ALBERT

Notes: The authors provide an account of current Directorate of Military Survey approaches to the provision of photocontrol by use of GPS and they pay special attention to the requirements of height control. 〈section xml:id="abs1-2"〉〈title type="main"〉SummaryGPS now provides us with a rapid method for determining plan and height for photogrammetric control directly over the points required by the photogrammetrist. By utilizing the slope of the geoid model, orthometric heights can be obtained to an accuracy of 0.15 m to 0.2 m. Surveys can be carried out quickly in all weather conditions and with none of the traditional terrestrial survey skills. Time, cost and manpower are greatly reduced. The plan accuracies are well within any requirements of the photogrammetrist and heights can be achieved to within 0.15 m to 0.2 m on test areas of UK. As photogrammetric height accuracy requires at best 1 m for plotting a 10 metre contour interval, heighting by GPS and the use of a geoid model solves the heighting problem.〈section xml:id="abs1-3"〉〈title type="main"〉Résumé Les auteurs fournissent un compte-rendu de la façon dont le Directorate of Military Survey aborde actuellement le problème de la fourniture de points ďappui photos avec ľemploi du GPS et prêterit une attention particulière à celui des points ďappui altimétriques.〈section xml:id="abs1-4"〉〈title type="main"〉Zusammenfassung Die Autoren geben einen Bericht über die gegenwärtigen Versuche beim Directorate of Military Survey zur Paβpunktbestimmung mit GPS, wobei sie den Anforderungen an die Höhenbestimmung besondere Aufmerksamkeit zollen.

Notes: The operational situation of precise airborne GPS positioning of camera air stations and its use in combined block adjustment for aerial triangulation is reviewed. The acceptance of systematic GPS errors, which occur especially with biased phase ambiguity solutions after loss of lock of signals in-flight, has motivated the method of additional linear GPS drift parameters which are to be solved in the combined block adjustment. It also implies that no absolute GPS co-ordinates are required and that the datum transformation is provided via a few ground control points. A great number of practical examples demonstrates that the method has been successfully applied within a wide range of photoscales and of block sizes. It has proved to be fully operational under various practical conditions. The high accuracy performance of GPS blocks and the economic benefit have been confirmed. It is particularly noticeable that the stationary receiver can be at a great distance, up to 500 km or more from the mission area. The conclusion is drawn that GPS supported aerial triangulation is ready to become standard. The potential improvement from dual frequency receivers and fast ambiguity solutions only enhances that conclusion. 〈section xml:id="abs1-2"〉〈title type="main"〉Résumé On examine, dans cet article, le degréďopérationnalité atteint par le GPS aéroporté dans le positionnement précis des sommets de prises de vues des caméras aériennes, et son insertion dans la compensation par blocs en aérotriangulation. La possibilityéďerreurs systématiques dans le GPS, en particulier en cas de perte des signaux en vol, qui se manifeste par des ambiguïtés de phase et des biais dans les résultats, à conduit a introduire dans la compensation en bloc des inconnues supplémental s, traduisant une dérive linéaire du GPS. II en résulte qu'il n'est pas nécessaire de disposer de coordonnées GPS absolues et que quelques points ďappui sur le terrain suffisent à assurer les changements de coordonnées. On a utilisé avec succès cette méthode dans de nombreux essaispratiques comportant un large eventail ďéchelles de prises de vues et de tallies des blocs. On a pu ainsi mettre en évidence ľentière opérationnalité de cette méthode, dans des conditions réelles différentes. On a également confirmé la haute précision des résultats des blocs GPS et les avantages économiques de ce système. En particulier, il est tout à fait remarquable que le récepteur fixe puisse se trouver à une grande distance de la zone du lasé, 500 km ou plus. On peut en conclure que ľaérotriangulation appuyée sur le GPS est en train de devenir une méthode standard. Les améliorations possibles que peuvent apporter les récepteurs à deux fréquences et la résolution rapide des ambiguïtés, ne font que renforcer cette conclusion. 〈section xml:id="abs1-3"〉〈title type="main"〉Zusammenfassung Die hochgenaue Kamera Positionierung durch GPS und ihre Anwendung für die Aerotriangulation wird zusammengefaβt dargestellt. Die Existenz systematischer GPS Fehler, wie sie inbesondere durch nur genäherte Phasen-Mehrdeutigkeitslösungen nach Signalabrissen im Flug verursacht werden, haben zu der speziellen Methode zusätzlicher linearer GPS Drift Parameter geführt, die in der kombinierten Blockausgleichung bestimmt werden. Ferner wird dabei die Datumtransformation mit Hilfe einiger weniger Paβpunkte bestimmt, d.h. es werden keine absoluten GPS Koordinaten vorausgesetzt. Mit einer groβen Zahl praktischer Beispiele wird demonstriert, daβ die Methode in einem groβen Bereich von Bildmaβstäben und Blockgröβen bereits erfolgreich angewendet wird. Sie hat sich unter den verschiedensten praktischen Bedingungen als voll operationell erwiesen. Dabei wurde die theoretisch erwartete hohe Genauigkeit der GPS Blöcke und ihre Wirtschaftlichkeit bestätigt. Besonders bedeutsam ist der empirische Nachweis, daβ der stationäre GPS Empfänger sehr weit, bis 500 km oder mehr, von dem Fluggebiet entfernt sein kann. Als Ergebnis wird empfohlen, die GPS gestützte Aerotriangulation als verfügbares photogrammetrisches Standardverfahren allgemein zu verwenden. Diese Schluβfolgerung wird durch die neuesten Entwicklungen von Zwei-Frequenz Empfängern und schnellen Mehrdeutigkeitslösungen, in die hohe Erwartungen gesetzt werden, nur noch bekräftigt.

Notes: Photogrammetrists are acutely aware that remote methods of survey are commonplace. However, it is only relatively recently that high precision levelling of the national motorway network has been conducted in this manner. There are now several competing methods available, all of which have gained some acceptance. This paper describes a low level aerial photographic method employing a helicopter as the platform. It begins with the reasons for the development, describes the system and methods involved, addresses the safety aspects, attempts to outline the necessity for the largest scale possible to maintain precision, analyses the potential developments and discusses the advantages and disadvantages compared with ground based systems.

Notes: An investigation has been made into the feasibility of using a low cost GPS receiver fitted to a light fixed wing aircraft as an aid to flying parallel flight lines for block aerial vertical photography. Two cases were examined: (I) the pilot controlled the heading of the aircraft according to the indications on the course deviation indicator of the GPS receiver; (2) the autopilot, being connected to the GPS receiver, controlled the heading of the aircraft. The results obtained for both sidelap and endlap were equal to or superior to those obtained with a CCTV system. 〈section xml:id="abs1-2"〉〈title type="main"〉RésuméOn a mené une recherche sur la faisabilité du GPS comme aide au maintien du parallélisme des axes de prises de vues d'un bloc de photographies aériennes verticales, en utilisant un récepteur GPS bon marché fié a un avion léger. On a examiné deux cas: (i) celui ou le pilote a maintenu le cap de l'avion en suivant les indications de l'index de changement de route du récepteur GPS; (ii) celui ou c'est le pilote automatique qui, par une liaison au récepteur GPS, a maintenu le cap de l'uvion. Les résultats obtenus pour le recouvrement latéral et l'extrgmité des bandes se sont révélés égaux ou supérieurs ii ceux obtenus avec un systPme CCTV.〈section xml:id="abs1-3"〉〈title type="main"〉ZusammenfassungEs wurde eine Untersuchung über die mögliche Nutzung billiger GPS-Empfanger, die in ein Kleinjlugzeug als Hilfsmittel zum Flug paralleler Bildstreifen für die blockweise Luftbildaufnahme eingebaut wurden, durchgefuhrt. Dabei wurden 2 Falle geprüft: (1) Der Pilot steuerte das Flugzeug entsprechend der Anzeige auf dem Kursindikator des GPS-Empfangers. (2) Der mit dem GPS-Empfänger verbundene Autopilot steuerte das Flugzeug. Die Ergebnisse sowohl für Querals auch Längsüberdeckung waren gleich oder besser als die mit einem CCTV-System erhaltenen.

Notes: Cartography andphotogrammetry have always been strongly linked and this paper emphasises a view of cartography as a process of spatial data representation, rather than as a method of creating a product, a map. Of course, the definition of cartography must change with developments in its practice. An outline of the historical background to the subject is presented, followed by a consideration of the relationship between the cartographer and the user of the product. The basic problems involved in the transfer of information from the complex real world to a generalized cartographic product are analysed and technological aspects of the discipline are described. Contemporary applications of cartography include hazard mapping, links with GIS, tactile products and electronic hydrographic representation, all of which represent customer driven progress. It is concluded that the future of cartography is, overall, dependent on a graphical representation of high quality being supplied to the end user, rather than on the methods used to attain this objective. 〈section xml:id="abs1-2"〉〈title type="main"〉Résumé La cartographie et la photogramétrie ont toujours été liées étroitement ľune àľautre, et ľ‘on souligne dans cet article ľ‘idée que la cartographie est un systéme de représentation des données à trois dimensions, plutôt qu‘un ensemble de procédés de fabrication ďun produit, la carte. II est évident que la définition de la cartographie doit changer au fur et à mesure que des évolutions apparaissent dans sa pratique. Aprés un aperçu du contexte historique de ce thème, on examine les relations qui se développent entre le cartographe et ľutilisateur du produit. On analyse les problèmes fondamentaux du transfert ďinformations du monde réel, complexe, à un produit cartographique géneralisé et ľ‘on décrit la technologie qu'utilise cette discipline. Les applications récentes de la cartographie concernent la cartographie des risques naturels, les relations avec les SIG, les cartes qui se lisent par le toucher, et la représentation electronique de ľ‘hydrographic produits qui tous sont issus de cheminements pilotés en aval, par le client. On en déduit que la cartographie est, àľ'avenir, par dessus tout fonction ďune represséntation graphique de haute qualityé fournie à un utilisateur final, plutôt que de processus utilisé pour parvenir à cet objectif.〈section xml:id="abs1-3"〉〈title type="main"〉Zusammenfassung Kartographie und Photogrammetrie waren immer eng verbunden, und dieser Beitrag betont starker eine Auffassung von der Kartographie als einem Prozeβ der Darstellung von Raumdaten als ein Verfahren zur Herstellung eines Erzeugnisses, der Karte. Natürlich muβ sich die Definition der Kartographie bei Entwicklungen in ihrer Praxis ändern. Es erfolgt eine Skizzierung des historischen Hintergrundes des Gegenstands, gefolgt von Betrachtungen zur Beziehung zwischen Kartographen und dem Nutzer des Erzeugnisses. Die mit der Übertragung von Informationen aus der komplexen realen Welt in ein generalisiertes kartographisches System verbundenen grundlegenden Probleme werden analysiert, und es werden technologische Aspekte der Disziplin beschrieben. Zeitgenössische Anwendungen der Kartographie schlieβen die Kartierung von Katastrophen, Verbindungen zu GPS, gefühlsmäβge Erzeugnisse und elektronische hydrographische Darstellungen ein, die alle den vom Nutzer beeinflufiten Fortschritt darstellen. Es wird geschluffolgert, daft die Zukunft der Kartographie vor allem von der graphischen Darstellung hoher Qualität, die dem Endnutzer geliefert wird, abhängig ist undnicht so sehr von den Methoden, me dieses Ziel erreicht wird.

Notes: The paper entitled The Photogrammetric Society Analogue Instrument Project was published in The Photogrammetric Record, 14(82): 565–582 (October 1993) and contained, as Appendix A, an extract from the Archive concerned with the history of the Zeiss Stereoplanigraph in Great Britain. In The Photogrammetric Record, 14(83): 769–782 (April 1994), three further Appendices were published which dealt with the Williamson Multiplex equipment and other instruments. In this third extract, the history of five other instruments of the Multiplex type are described. This brings to a close that section of the Archive dealing with instruments using direct optical projection.〈section xml:id="abs1-2"〉〈title type="main"〉Résumé On a publicé dans le numéro 14(82) (pp 565–582) ďoctobre 1993 du“Photogrammetric Record”ľarticle intitulé“le projet de la Société (britannique) de Photogrammétrie sur les instruments analogiques” et inséré dans ľannexe A un extrait des Archives relatif a ľhistorie du Stereoplan-igraphe Zeiss en Grande-Bretagne. On a publicé dans le numéro 14 (83) ďavril 1994 du“Photogrammetric Record”(pp 769–782) trois annexes supplémentaires qui traitaient de ľappareil Multiplex de Williamson et ďautres instruments. Dans ce troisième extrait, on présente ľhistorie de cinq autres appareils du type Multiplex. Cette partie des Archives qui traitait des appareils basés sur ľemploi ďuneprojection optique directe, se trouve ainsi achevee.〈section xml:id="abs1-3"〉〈title type="main"〉Zusammenfassung Der Beitrag mit dem Titel“The Photogrammetric Society Analogue Instrument Project”wurde im Photogrammetric Record, 14(82): 565–582 (Oktober 1993) veröffentlicht und enthielt als Anlage A einen Extrakt vom Archiv, das mit der Geschichte des Zeiss Steroplanigraph in Groβbritannien verbunden war. Im Photogrammetric Record, 14(83); 769–782 (April 1984) wurden 3 weitere Anlagen veröffentlicht, die vom Williamson Multiplex und anderen Geräten handelten. In diesem 3. Auszug wird die Geschichte von 5 anderen Geräten des Multiplex-Typs beschrieben. Das führt zum Abschluβ desjenigen Teils des Archivs, das sich mit Geräten mit direkter optischer Projektion befaβt.

Notes: An analysis is given of the modelling of XY stage errors in an analytical plotter by polynomial functions. This is discussed as an alternative to demanding strict mechanical accuracy in the stage construction. In an era of plentiful computational resources, it is concluded that apportioning more of the responsibility to the mathematical co-ordinate refinement is an effective strategy. A second degree polynomial is used for each of the two stages in an analytical plotter, modelling the systematic stage errors to within the variability of a single observation. A requirement for instrument stability is emphasized. Such techniques have application for other instruments such as image scanners. 〈section xml:id="abs1-2"〉〈title type="main"〉Résumé On étudie la modélisation des erreurs des chariots XY ďun restituteur analytique en utilisant des fonctions polynomials. II s‘agit en fait de trouver une alternative à des exigences de prêcision mêcanique très strictes dans la réalisation de ces chariots. A une époque oùľon dispose ďune abondance de ressources en moyens de calcul, il apparait en effet relever ďune stratégie efficace de s'appuyer davantage sur les traitements mathématiques pour améliorer les valeurs des coordonnées. On utilise, pour chacun des deux chariots, un polynome du second degrè pour modéliser les erreurs systématiques des chariots, et les rendre inférieures aux erreurs propres à une observation unique. On insiste sur la nécessitéďune grande stabilityé instrumental. Ces processus peuvent également s'appliquer àďautres instruments comme les scanneurs ďimages. 〈section xml:id="abs1-3"〉〈title type="main"〉Zusammenfassung Es wird die Modellierung von Fehlern des xy-Wagens bei analytischen Auswertegeräten mit Hilfe von Polynomen analysiert. Des wird als Alternative zur Forderung nach einer strengen mechanischen Genauigkeit bei der Bildwagenkonstruktion diskutiert. Im Zeitalter hervorragender Computer-Ressourcen, so wird geschluβfolgert, ist es eine effektive Strategie, sich mehr der mathematischen Koordinatenverbesserung zuzuwenden. Ein Polynom 2. Grades wird für jeden der 2 Bildträger eines analytischen Auswertegerätes genutzt, um die systematischen Fehler im Bereich der Variation von einzelnen Beobachtungen zu modellieren. Bezüglich der Stabilität des Instruments wird eine Anforderung formuliert. Solche Verfahren kännen auch bei anderen Geräten, wie zum Beispiel Bildscanner angewendet werden.

Notes: This paper discusses analytical relative orientation for two-media photogrammetry. After a brief introduction concerning the collinearity condition, the coplanarity equation is derived, which is similar inform to the conventional expression. By considering the differences from one-medium photogrammetry, the computational strategy of relative orientation for two-media photogrammetry is studied, including linearization of the equation, the correction for refraction and, especially, the determination of the boundary between the two media. Simulated test results verify the theoretical analysis. 〈section xml:id="abs1-2"〉〈title type="main"〉Résumé On étudie dans cet article ľ orientation relative analytique dans la photogrammétrie à deux milieux. Après une brève introduction relative à la condition de colinéarité, on en dérive les équations de coplanarité dont la forme est tout à fait semblable à celle du cas classique. On dégage ensuite une stratégie de calcul de ľ orientation relative pour la photogrammétrie à deux milieux, en s'attachant aux différences avec celle à un seul milieu, et en mentionnant la linéarisation des équations, la correction de la réfraction et, plus particulièrement, la détermination de la limite entre les deux milieux. Les résultats obtenus sur des simulations sont conformes àľ‘analyse théorique. 〈section xml:id="abs1-3"〉〈title type="main"〉Zusammenfassung ImArtikelwirddie analytische relative Orientierung für die Zweimedien-Photogrammetrie diskutiert. Nach einer kurzen Einführung, die sich mit der Kollinearitätsbedingung befaβt, weden Komplanaritätsgleichungen ähnlich der konventionellen Form abgeleitet. Unter Beachtung der Unterschiede zur Einmedium-Photogrammetrie wird die rechnerische Strategic der relativen Orientierung für die Zweimedien-Photogrammetrie studiert. Das schließt die Linearisierung der Gleichungen, die Refraktionskorrektur und besonders die Bestimmung der Grenze zwischen den beiden Medien ein. Simulierte Testergebnisse bestdtigen die theoretische Analyse.

Notes: Treaty verification involves the acquisition and interpretation of data to establish a country's compliance to an agreement. Remote sensing and photogrammetry in verification is established in the intelligence community and is progressively entering the civilian sector as well. The Open Skies Treaty and the proliferation of commercial satellite imagery have created a niche for open, multilateral verification. These recent developments come at an opportune moment as the verification task has become more cumbersome and complex.This paper surveys the changes in the field of verification, aerial monitoring and satellite surveillance. It details existing and future verification tasks and presents the operational capabilities for fulfilling those tasks. The limiting factors are also presented.

Notes: In a continuing drive to reduce the radiation exposure of nuclear workers, many routine aspects of nuclear plant maintenance and refurbishment are increasingly undertaken by robotic or remote handling tools. Accurate “as built” documentation of plant records is vital to the successful planning and execution of such operations since an unexpected obstruction or undocumented site modification may result in a costly disruption or even failure of the intervention. In recognition of the importance of such documentation, a recent European Community† sponsored project has been directed towards the development of techniques for cost effective survey and modelling of such plant. This paper will detail the rationale behind the design of such a system and will describe typical results from a number of pilot projects.

Notes: Some of the economic and operational aspects of mapping are discussed, including the conditions that may offer air survey a competitive advantage over other methods. The financing of national mapping programmes around the world is increasingly market oriented, driven by the need to provide the end users with information that they can turn into sustainable economic growth and social progress. Despite these economic pressures, map makers seem to find their work more enjoyable and rewarding than most professionals.

Notes: A description is given of a heighting accuracy test carried out at Cartographical Services Limited on 1:2000 scale aerial photography. Premarked points, with ground surveyed heights, were established on a dual carriageway road near Worcester and photography was flown using a Leica RC20 aerial camera with EMC. Photogrammetric height measurement was carried out with both a Zeiss P3 analytical plotter and a Cartographic Engineering Limited/Carto Instruments AP190 plotter; respective r.m.s.e. accuracies of ± 25 mm and ± 30 mm were obtained. The new Cartographic Engineering Limited CP2 analytical plotter has subsequently been used for height measurement on similar photography and comparable accuracy has been achieved. 〈section xml:id="abs1-2"〉〈title type="main"〉Résumé On présente un essai de précision altimétrique, effectué par la Société“Cartographical Services” de Southampton, sur des photographies aérienne àľéchelledu 1:2000. On a utilisé des points pré-balisés, repartis sur une route à double voie près de Worcester, et dont ľaltitude a été déterminé sur le terrain. La prise de vue a été fait avec une caméra Leica RC20 munie ďun système de compensation du filé longitudinal. On a effectué les déterminations photogrammétriques des altitudes en utilisant à la fois un restituteur analytique Zeiss P3 et une restituteur AP190 de la Société“Cartographic Engineering/Carto Instruments.” On a obtenu comme erreurs moyennes quadratique les valeurs de ± 25 mm et ± 30 mm respectivement. On a enfin utilisé le noveau restituteur analytique CP2 de la Société“Cartographic Engineering” pour ces déterminations altimétriques et ľon a obtenu une précision comparable. 〈section xml:id="abs1-3"〉〈title type="main"〉Zusammenfassung Es wird ein Versuch zur Bestimmung der Höhengenauigkeit, der beim Cartographical Services Ltd. in Southampton für den Bildmaβstab 1:2000 durchgeführt wurde beschrieben. Signalisierte Punkte, deren Höhen im Gelände bestimmt wurden, wurden aufeiner Doppelfahrbahn in der Nähe von Worcester angeordnet undmit einerLeica RC20 mit EMC aufgenommen. Die photogrammetrische Höhenbestimmung erfolgte mit einem analytischen Auswertegerät P3 von Zeiss und einem AP 190 Plotter von Cartographic Engineering Ltd./Carto Instruments. Dabei wurden mittlere Fehler von ± 25 mm bzw. ± 30 mm erhalten. Das neue analytische Auswertegerät CP 2 von Cartographic Engineering Ltd. wurde danach für Höhenmessungen bei ähnlichen Luftbildern genutzt, wobei vergleichbare Genauigkeiten erreicht wurden.

Notes: This paper describes a method for modelling the SPOT satellite imaging process using a single Ground Control Point (GCP) and for extracting ground planimetric information. Satellite position is derived using the collinearity condition equations. Initial orbit is obtained from the given ephemeris data and refinement is carried out using an iterative least squares solution. Attitude variations are taken into account by fitting a third order polynomial in time to the attitudes derived from the ephemeris by integration. After refining the satellite position, planimetric co-ordinates can be derived using the collinearity equations with an accuracy of up to 38 m in latitude and 52 m in longitude (average of the r.m.s. errors from two tests) when the GCP used for modelling is obtained from the 1:50 000 scale map. These figures include the measurement errors as well as the modelling error. It has been found that the method is not sensitive to the location of the GCP used for modelling. Résumé On présente dans cet article une méthode de modélisation du traitement des images du satellite SPOT ne faisant appel qu'à un seul point ďappui au sol et permettant ďextraire des informations planimétriques. On obtient la position du satellite à partir des équations traduisant la condition de colinéarité. On part ďune orbite initiale issue des données fournies par les éphémerides, et on ľameliore par une résolution itèrative, basée sur les moindres carrés. On tient compte des variations ďattitude par ľintermédiaire ďun polynome du troisième ordre fonction du temps et correspondant aux attitudes dérivées des éphémérides par intégration. Une fois obtenue la position définitive du satellite, on peut tirer les coordonnees planimétriques des équations de colinéarité avec une précision qui atteint 38 m en latitude et 52 m en longitude (valeurs moyennes des erreurs moyennes quadratiques rèsultant de deux essais), lorsque le point ďappui au sol utilisé dans la modélisation provident de la carte au 1:50 000. Ces chiffres incluent les erreurs de mesure ainsi que ľerreur de modélisation. On a trouvé que la méthode nétait pas du tout sensible à la position qu'occupait le point ďappui au sol utilisé dans le modélisation. 〈section xml:id="abs1-2"〉〈title type="main"〉Zusammenfassung Im Artikel wird ein Verfahren zur Geländemodellierung des SPOT-Abbildungsprozesses unter Verwendung eines einzelnen Geländepaβpunktes (GCP) und zur Ableitung planimetrischer Informational beschrieben. Die Satellitenposition wird mit Hilfe der Kollinearitätsgleichungen beschrieben. Die Näherungswerte für die Bahnkurve werden aus gegebenen Ephemeriden bestimmt, die durch einen iterativen Prozeβ nach der Methode der kleinsten Quadrate verbessert werden. Veränderungen der Bahn werden rechtzeitig durch Anpassung mit einem Polynom 3. Grades an die aus den Ephemeriden abgeleitete Bahn durch Integration angepaβt. Nach Verbesserung der Satelliten-position können die Lagekoordinaten mit Hilfe der Kollinearitätsgleichungen mit einer Genauigkeit bis zu 38 m in der Breite und 52 m in der Länge (Mittelwert der mittleren Fehler aus 2 Versuchen) bestimmt werden, wenn der Paβpunkt (GCP) aus einer Karte 1:50 000 entnommen wurde. Dabei ist der Meβfehler ebenso wie der Modellierungsfehler enthalten. Es zeigte sich, daβ das Verfahren nicht empfindlich ist in bezug aufdie Lage des zur Modellierung benutzten Paβpunktes.

Notes: Book Reviewed in this article:THE MICROSCOPIC PHOTOGRAPHS OF J. B. DANCER. By B. Bracegirdle and J. B. McCormick.ROBOT CALIBRATION. Edited by R. Bernhardt and S. L. Albright.BASIC CARTOGRAPHY FOR STUDENTS AND TECHNICIANS: VOLUME 1. Second edition. Edited by R. W. Anson and F. J. Ormeling.A HALF AND HALF AFFAIR: CHRONICLES OF A HYBRID DON. By D. R. Denman.IMAGE INTERPRETATION IN GEOLOGY. Second edition. By S. A. Drury.VERMESSUNG UND ORTUNG MIT SATELLITES NAVSTAR-GPS UND ANDERE SATELLITENGESTUTZTE NAVIGATIONSSYSTEME. Second edition. By M. Bauer.HANDBOOK OF THE MOIRE FRINGE TECHNIQUE. By K. Patorski.LANDSCAPE ECOLOGY AND GEOGRAPHIC INFORMATION SYSTEMS. Edited by R. Haines-Young, D. R. Green and S. H. Cousins.INTRODUCTION TO INTEGRATED GEO-INFORMATION MANAGEMENT. By S. Cassettari.GEOGRAPHIC INFORMATION 1994: THE SOURCE BOOK FOR GIS. Edited by D. R. Green, D. Rix and J. Cadoux-Hudson.CAMERAS, SCANNERS, AND IMAGE ACQUISITION SYSTEMS. Edited by H. C. Marz and R. L. Nielsen.INVENTORY OF WORLD TOPOGRAPHIC MAPPING. Volume 3, Eastern Europe, ASIA, Oceania and Antarctica. Compiled by R. Böhme. English language editor R. Anson.POSTPROCESSING VON SAR-SATELLITENBILDDATEN. By F. Holecz.DISPLAY SYSTEMS. Edited by C. T. Bartlett and M. D. Cowan.STEREOSCOPIC DISPLAYS AND VIRTUAL REALITY SYSTEMS. Edited by S. S. Fisher, J. O. Merritt and M. T. Bolas.

Notes: Photographic lenses are produced in a variety of types for numerous image formats. Innovations in optical technology enable technically advanced lenses to be produced and camera systems improved. Following descriptions of computer aided design and manufacture and the importance of new optical materials, aspheric surfaces and floating elements, several types of lenses are described in detail, including zoom, soft focus, high resolution, micro, large format and telephoto designs. Also discussed are optical attachments and the optical systems of compact cameras, viewfinders and three-chip video cameras.

Notes: A case is made for the development of an inexpensive and portable data capturing unit which could be used with existing mirror stereoscopes and which could provide an accuracy sufficient for most digital map databases. The results of simulation experiments to test the accuracy of the system are presented.

Notes: The pianoforte in the Mozarthaus at Salzburg is a state of the art instrument of the late 18th century. It was recorded photogrammetrically in order to enable fundamental musicological investigations to be carried out. An important aspect of the piano survey was high precision three dimensional point determination performed by combined bundle adjustment. The process was optimized by use of software tools for simulation, automatic error detection and graphical analysis of the adjustment results. This procedure considerably increased the efficiency and reliability of the photogrammetric reconstruction.

Notes: Although accuracy of digital elevation models (DEMs) can be quantified and measured in different ways, each is influenced by three main factors: terrain character, sampling strategy and interpolation method. These parameters, and their interaction, are discussed. The generation of DEMs from digitised contours is emphasised because this is the major source of DEMs, particularly within member countries of OEEPE. Such DEMs often exhibit unwelcome artifacts, depending on the interpolation method employed. The origin and magnitude of these effects and how they can be reduced to improve the accuracy of the DEMs are also discussed.

Notes: : Water marketing has been proposed as one means of reallocating water supplies in the western United States. While markets for western water currently exist and may be expected to expand, the institutional constraints within which the markets must operate will limit the ultimate size and efficiency of those markets. Lack of articulation of public interests in the water resource itself leads to incomplete definition of the private rights to use the water, and it is those private rights which are sold or leased in the market. The increase in size and efficiency of any market in water rights will be dependent on the willingness of legislatures to specifically define the nature and extent of public interests in water supplies, and detailed definition is unlikely.

Notes: : Diquat herbicide and rhodamine WT dye were applied in a lake to three 1.6 ha plots either with a polymer, which reportedly aids in sinking and confinement of aquatic herbicides, or without a polymer. Diquat and dye concentrations were measured at three different depths in the water column within the plots during the first three hours after application to determine vertical distribution of diquat and dye, and in composite samples at fixed distances from the plot up to 168 hours after application to determine movement out of the treated plots. Diquat and dye were homogeneous in the water column when no polymer was used, but were concentrated near the surface when polymer was used. This distribution may have resulted from temperature stratification. Polymer did not affect movement of diquat or dye out of the plots. The half-lives of diquat within the plots were 25 (SE=6.2) hr, 39 (SE=4.3) hr, and 25 (SE=2.0) hr. Forty-six percent of samples collected at the edges of the plots did not contain detectable diquat residues and only 66 percent of those samples with detectable diquat contained greater than the potable water tolerance (10 ppb). Diquat was not found in any samples 168 hours after application 61 m or farther from the edge of the plots. Dye and diquat concentrations were weakly correlated within and outside the plots. Dye half-lives were consistently higher than diquat, which suggests that the herbicide was removed from the water by plants and sediments more rapidly than dye.

Notes: : Water marketing is an increasing important topic for policy makers and water managers, especially in the Western United States. Indian reserved rights (or Winters rights) differ in significant ways from water rights under most state prior appropriation systems. As Winters rights are quantified, a number of issues are emerging concerning the extent to which these water rights may be marketed, particularly to off-reservation users. This paper will review the evolution of Indian reserved water rights and discuss key issues surrounding the marketing of these rights.

Notes: : The concentrations of dissolved fixed inorganic nitrogen (ΣN) in Bermuda ground waters can be very high due to both natural and anthropogenic processes. The high anthropogenic flux is due to domestic cesspit operation. Mass balance calculations indicate that ground water seepage, especially rich in ΣN, is a major source of nutrients into the near shore coastal zone of Bermuda. The ground water flux of ΣN is approximately 1.5 to 4 times that of the sewage flux of ΣN to Bermuda's nearshore waters. This input of ΣN may be important in the development of algal blooms in these waters. Our work, coupled with other recent investigations, suggests that the ground water input of nutrients into nearshore marine waters is an important process globally.

Notes: : Voluntary water transfers through markets have been advocated by many diverse groups as a means to reallocate scarce water supplies in the semi-arid western U.S. Although transfers of water rights have occurred almost since the creation of prior appropriation laws over a century ago, functioning water markets have been very slow to develop and are few in number. The structure, composition, administration and transactions of one of the most well established water markets, shares in the Bureau of Reclamation, Colorado-Big Thompson project, are examined to better understand the institutional and transfer conditions that sustain an active water market. Results from a detailed study of C-BT project records reveal that between 1970 and 1993 there were 2,698 transactions through which over one-third of the project water changed ownership or type of use. Further analysis shows that the transactions involved many individual sellers and categories of buyers with different uses, including agricultural buyers. The transfer activity and efficiency of the C-BT market has lead some to suggest that it be used as a model for other markets. However, because this market has fewer institutional restrictions, a well developed infrastructure and unique market conditions, it will be difficult to transfer this model to other areas without accompanying modifications in water right administration and institutions.

Notes: : Recent stream survey data (1989–1993) from 31 stream segments of 21 streams within the upper South Umpqua Watershed Oregon were compared to 1937 stream survey data collected from these same stream segments. Current low-flow wetted stream widths of 22 of the 31 surveyed stream segments were significantly different than in 1937; 19 stream segments were significantly wider while the remaining three stream segments were significantly narrower. In only 1 of 8 tributaries to the South Umpqua River which had headwaters within land designated wilderness area did low-flow stream channel width increase since 1937. Conversely, 13 of the 14 tributaries to the South Umpqua River which originated from lands designated as timber emphasis were significantly wider than in 1937. The observed change in stream width was linearly related to timber harvest (r2= 0.44), road density (r2= 0.45), and the amount of large organic debris remaining within the active stream channel (r2= 0.43). These findings suggest that timber harvest and road construction may have resulted in changes in channel characteristics. These channel changes may also be a factor in the observed decline of three of the four populations of anadromous salmonids within the basin.

Notes: : To quantify the effectiveness of best management practice (BMP) implementation on runoff, sediment, and nutrient yields from a watershed, the Nomini Creek watershed and water quality monitoring project was initiated in 1985, in Westmoreland County, Virginia. The changes in nonpoint source (NPS) loadings resulting from BMPs were evaluated by comparing selected parameters from data series obtained before, during, and after periods of BMP implementation. The results indicated that the watershed-averaged curve number, sediment, and nutrient (N and P) concentrations were reduced by approximately 5, 20, and 40 percent, respectively, due to BMP implementation. The nutrient yield model developed by Frere et al. (1980) was applied to the water quality parameters from 175 storms, but it failed to adequately describe the observed phenomena. Seasonal changes in nutrient availability factors were not consistent with field conditions, nor were they significantly different in the pm- and post-BMP periods. An extended period of monitoring, with intensive BMP implementation over a larger portion of the watershed, is required to identify BMP effectiveness.

Notes: : Simulation of ground-water flow and fate of contaminants in the subsurface environment constitutes a major phase of most environmental assessment and site remediation studies. These simulation studies yield information on spatial and temporal distributions of contaminants in the subsurface media. An important use of this information is to conduct exposure assessment studies. Spatial and temporal distributions of both chemical concentrations and exposed populations render this integrated exposure analysis task rather difficult. Geographic Information Systems (GIS), on the other hand, provide a platform in which layered, spatially distributed databases can be manipulated with ease, thereby simplifying exposure analysis tasks significantly. In this paper, we describe procedures that combine the simulation models and demographic databases under a GIS platform to automate the exposure assessment phase of a typical health assessment study. Procedures developed herein significantly simplify the post-processing phase of the analysis, and render the overall task more ‘user friendly.’ A site-specific application is included as a demonstration of the proposed process.

Notes: : Suspended solids and ammonium concentration profiles measured at five locations in Duluth-Superior Harbor during July-October 1985 were analyzed to quantify wind and ship effects on sediment resuspension and resulting harbor water quality. Wind components from the SE quadrant correlated strongly with depth-averaged suspended solids concentrations that were unaffected by ship passage or thermal stratification. Winds from that quadrant have the largest fetch in the harbor. The highest correlation (r2= 0.93) was with the 6-hour average of the ESE wind velocity component. Multiple linear regression analysis of data from post-ship passage concentration profiles yielded numerical estimates of settling velocities of 0.08 to 0.25 cm s−1, typical of ship-resuspended sediments, and vertical eddy diffusivities of 4 to 13 cm2 s1. The results suggest that ambient vertical eddy diffusivities in the harbor are less than 4 cm2 s−1 in the absence of ship passages and with winds less than 5 m s−1 (10 knots).

Notes: : Design of a stormwater pump station is a complicated procedure because of the large number of parameters that are involved. Even the most basic pump station serving a small catchment requires a computationally intensive iterative evaluation. However, the design problem consists primarily of finding the combination of temporary storage and pump capacity that accommodates runoff of the selected recurrence interval for the least cost. A procedure is developed for rapidly obtaining the needed relation between storage volume and discharge for small pump stations where a constant outflow can be assumed and the inflow hydro-graph can be represented using the modified rational method with rainfall given by a widely-used intensity-duration equation. Accepting the limitations of the modified rational method and the simplifications applied to pump station operation, the procedure provides an uncomplicated way of rapidly finding the stormwater runoff volume that needs to be temporarily stored for given values of pump discharge and activation water level (or, equivalently, activation storage volume). Ultimate determination of temporary runoff storage will depend on an economic analysis of the trade-off between storage volume and pump capacity.

Notes: : Current conventions for reporting analytical results from environmental samples brings the objectives of laboratory scientists into conflict with those of environmental scientists. The objective of chemical analyses is to provide estimates of the true composition of samples. Reported results must reflect the analytical uncertainty. Current conventions require left-censoring of those results below the Limit of Detection. The objective of statistical interpretation of environmental data is to provide estimates of the characteristics of ecosystems. Such statistical analyses are often confounded by left-censoring of analytical results. We review the different points of view and propose a compromise which recognizes these conflicting perspectives.

Notes: : Most hydrologic models require input parameters which represent the variability found across an entire landscape. The estimation of such parameters is very difficult, particularly on rangeland. Improved model parameter estimation procedures are needed which incorporate the small-scale and temporal variability found on rangeland. This study investigates the use of a surface soil classification scheme to partition the spatial variability in hydrologic and interrill erosion processes in a sagebrush plant community. Four distinct microsites were found to exist within the sagebrush coppice-dune dune-interspace complex. The microsites explained the majority of variation in hydrologic and interrill erosion response found on the site and were discernable based on readily available soil and vegetation information. The variability within each microsite was quite low and was not well correlated with soil and vegetation properties. The surface soil classification scheme defined in this study can be quite useful for defining sampling procedures, for understanding hydrologic and erosion processes, and for parameterizing hydrologic models for use on sagebrush range-land.

Notes: : According to the 1990 National Water Quality Inventory nutrient runoff from agriculture is one of the largest contributors to watershed contamination. Nutrient balance studies suggest that many farmers use more fertilizer than necessary because of insufficient crediting for nutrients coming from manure and legumes. Using data from the USDA's 1990 Farm Costs and Returns Survey, we found that farmers raising only conventional crops spend between $470 to $624 million more per year on fertilizer than necessary. This accounts for a range of 24 percent to 32 percent of total annual nitrogen (N) purchases. The excess N amounts to between 2.5 to 3.3 billion pounds N and has considerable water pollution potential. Farmers and the fertilizer industry have responded positively to highly focused research and education programs which support improved crediting of these nutrients.

Notes: : Injection of water and subsequent withdrawal were carried out in three existing water wells (SU-10, C-105, and SU-135A) in Kuwait. The objective of the study was to assess the technical feasibility of artificial recharge in the carbonate Dammam Formation and the clastic Kuwait Group aquifers. In the absence of any pretreatment of injection water and measures for maintenance of line pressure, clogging from suspended solids and air entrapment occurred in all three experiments. It was, however, possible to inject for one month in Wells SU-10 and C-105 where injection took place in the Dammam aquifer. In Well SU-135A, where the Kuwait Group aquifer was the target for injection, clogging became so severe that the injection experiment had to be abandoned. The injection/withdrawal data were analyzed with the help of a multi-aquifer flow model and a transport model. The models took into account the effects of crossflow within the boreholes on the distribution of intake and discharge rates for different aquifers, and hence, on the recovery efficiency. The experiments suggested that the artificial recharge of the Dammam and the Kuwait Group aquifers was technically feasible. The problem of clogging was, however, more severe for the Kuwait Group.

Notes: : This paper first presents a brief review of an earlier effort to estimate the benefits associated with achieving the Clean Water Act objectives. It then discusses what would be involved in doing a retrospective benefit-cost analysis of the Clean Water Act and some information on changes in several measures of water quality over the past 20 years. The paper concludes with a summary of a recent effort to estimate the realized benefits associated with the Clean Water Act and some implications for policy. (KEY TERMS: benefits; benefit-cost analysis; costs; recreation; water pollution; water quality.)

Notes: : This paper summarizes key provisions of the Clinton Administration's proposals for change in the Clean Water Act. Two of the important themes for change are tougher controls for non-point source pollution and the use of market-based instruments. A detailed analysis of market-based abatement suggests limited potential for reducing costs. The keys to nonpoint source pollution control are clearer definition of property rights combined with changes in government programs that encourage polluting activities.

Notes: : The degree of progress achieved under the 1972 Clean Water Act is reviewed by reference to traditional measures of program implementation, and to evidence of tangible, or “real-world” progress, such as beach closures, drinking water contamination, fishing bans and advisories, species health, and habitat degradation. Significant progress has been made in reducing pollution from point sources, but large point source releases of toxic and other pollutants remain. Little progress has been made in addressing runoff pollution, and in protecting aquatic habitats. Clean Water Act reauthorization should focus on pollution prevention to reduce further the release of toxics by point sources, a new program of mandatory but flexible controls on sources of runoff, and watershed protection programs to promote habitat protection and restoration. Economic factors should be considered in Clean Water Act programs, but must be balanced against scientific and governmental factors as well.

Notes: : Salinity increases in water in some parts of the Nava-jo aquifer in southeastern Utah have been documented previously. The purpose of this paper is to use bromide, iodide, and chloride concentrations and del oxygen-18 and deuterium values in water from the study area to determine if oil-field brines (OFB) could be the source of increased salinity. Mixing-model results indicate that the bromide-to-chloride X 10,000 weight ratio characteristic of OFB in and outside the study area could not be causing the bromide depletion with increasing salinity in the Navajo aquifer. Mixing-model results indicate that a mixture of one percent OFB with 99 percent Navajo aquifer water would more than double the bromide-to-chloride weight ratio, instead of the observed decrease in the weight ratio with increasing chloride concentration. The trend of the mixing line representing the isotopically enriched samples from the Navajo aquifer does not indicate OFB as the source of isotopically enriched water; however, the simulated isotopic composition of injection water could be a salinity source. The lighter isotopic composition of OFB samples from the Aneth, Ratherford, White Mesa Unit, and McElmo Creek injection sites relative to the lsmay site is a result of continued recycling of injection water mixed with various proportions of isotopically lighter make-up water from the alluvial aquifer along the San Juan River. A mixing model using the isotopic composition of the simulated injection water suggests that enriched samples from the Navajo aquifer are composed of 36 to 75 percent of the simulated injection water. However, chloride concentrations predicted by the isotopic mixing model are up to 13.4 times larger than the measured chloride concentrations in isotopically enriched samples from the Navajo aquifer, indicating that injection water is not the source of increased salinity. Geochemical data consistently show that OFB and associated injection water from the Greater Aneth Oil Field are not the source of salinity increases in the Navajo aquifer.

Notes: : A synoptic sampling of five surface-water sites in central Nebraska was conducted by the U.S. Geological Survey as part of its National Water-Quality Assessment Program during storm runoff in May 1992 to relate transport, yields, and concentrations of atrazine to environmental setting. Atrazine was the most extensively applied pesticide in the study unit. Atrazine transport was related to the size of contributing drainage area, quantity of atrazine applied, amount of precipitation, and volume of stream-flow. Estimated yields and mean concentrations of atrazine were related to the percentage of cropland in a drainage area. The largest estimated yields and mean concentrations of atrazine in surface water were associated from drainage areas with the highest percentage of cropland, and the smallest was associated with the smallest amount of cropland. Atrazine concentrations increased as streamflow increased but decreased at or near the time of peak streamflows, perhaps due to dilution. Atrazine concentrations then increased and remained elevated far into the stream recession. Atrazine is a regulated contaminant in finished public-water supplies. Large concentrations of atrazine could affect the management of public-water supplies because atrazine remains in solution in contrast to many other pesticides that are more easily removed.

Notes: : The sensitivity of streamflow to climate change was investigated in the American, Carson, and Truckee River Basins, California and Nevada. Nine gaging stations were used to represent streamflow in the basins. Annual models were developed by regressing 1961–1991 streamflow data on temperature and precipitation. Climate-change scenarios were used as inputs to the models to determine streamflow sensitivities. Climate-change scenarios were generated from historical time series by modifying mean temperatures by a range of +4°C to—4°C and total precipitation by a range of +25 percent to -25 percent. Results show that streamflow on the warmer, lower west side of the Sierra Nevada generally is more sensitive to temperature and precipitation changes than is streamflow on the colder, higher east side. A 2°C rise in temperature and a 25-percent decrease in precipitation results in stream-flow decreases of 56 percent on the American River and 25 percent on the Carson River. A 2°C decline in temperature and a 25-percent increase in precipitation results in streamflow increases of 102 percent on the American River and 22 percent on the Carson River.

Notes: : Spatial distributions of nitrogen and phosphorus in water were related to environmental setting as part of a regional water-quality assessment of the Central Nebraska Basins. The environmental settings (Sandhills, Loess Hills, Glaciated Area, and Platte Valley) were characterized by different concentrations of nitrogen and phosphorus in ground water and stream water. Statistically significant differences in nitrate concentrations in both ground-water and stream-water samples were related to regional distributions of cropland and rangeland. Nitrate concentrations were larger, especially in shallow ground water, in environmental settings dominated by cropland and associated fertilizer use than in settings dominated by rangeland. Similarly, total-nitrogen and nitrate concentrations were relatively large in selected streams draining primarily cropland. Comparative concentrations of phosphorus in stream water on the basis of environmental setting were similar to those of nitrogen, although the largest phosphorus concentrations probably relate to wastewater discharge into small streams. Nitrogen and phosphorus concentrations in much of the Platte River apparently reflected the quality of water entering the study unit from upstream and limited base-flow contributions from within the Platte Valley itself.

Notes: : The 1986 Amendments to the Safe Drinking Water Act mandate a multifaceted approach to wellhead protection. This approach includes: (1) delineating wellhead protection areas; (2) identifying and managing potential contaminants; (3) developing contingency plans in the event of weilfield contamination; (4) siting new wells; and (5) encouraging public participation. These elements encompass technical, administrative, and educational considerations. In functioning both as a research tool and as a decision support system, a geographic information system (GIS) is shown to have proven utility in addressing these issues. This article describes the application of common GIS functionality in facilitating a comprehensive wellhead protection scheme for an agricultural municipality in North Dakota.

Notes: : Economic theory clearly indicates that the use of increasing rate structures will reduce the demand for water and produce monetary incentives for consumers to conserve. One problem with estimating the effectiveness of using rate structures as a conservation program is that they are usually accompanied by other conservation efforts. Thus, it is difficult to determine the effectiveness of any one conservation component. This paper examines the effectiveness of increasing rate structures in a situation where no other conservation program was introduced. The paper uses customer data from the Spalding County (Georgia) Water Authority where an increasing rate structure replaced a descending rate structure in January 1991. Since the imposition of the increasing rate structure, the number of customers has increased 21 percent while total water demand has gone up only 15 percent and per customer water use has declined 5 percent. The daily water use per connection has declined from 243 gallons in 1990 to 231 in 1993, and monthly use has gone from 7,381 gallons to 7,028 per connection over the same period. Statistical tests indicate that water consumption during the two periods was significantly different while weather factors were not.

Notes: : Under an approved remining program, a coal mine operator can remine abandoned sites without legally assuming treatment responsibilities of the previously degraded water, as long as these discharging waters are not further degraded. Determination of discharge degradation caused by remining of abandoned coal mines requires knowledge of mine water quality and discharge flow rate characteristics both before and after remining. Normality tests performed on the water quality and flow data from 57 mine discharges indicate generally nonnormal distributions and extreme right-skewness. Exploratory data analysis (notched box-and-whisker plots) of the differences among medians indicates that the water quality of underground mines was more highly degraded in terms of acidity, iron, and sulfate concentrations than that from surface mines. Spearman's rank correlation tests, normality testing, and exploratory data analysis indicate that discharge flow rate is the primary controlling factor on the variability of pollution load rate. Reduction of recharge from the surface and adjacent unmined strata should decrease the mine discharge flow rate and in turn the pollution load.

Notes: : An integrated, multi-disciplinary effort to model land processes affecting Mayaguez Bay in western Puerto Rico is described. A modeling strategy was developed to take advantage of remotely sensed data. The spatial, interannual, and seasonal variability of sediment discharges to the bay were also evaluated. Classified images of remotely sensed data revealed the spatial distribution and quantities of land use classes in the region and aided in the discretization of the watershed into homogeneous regions. These regions were modeled using a geomorphic modeling technique based upon spatially averaged parameters.Simulation results from the modeling effort compared favorably with observations at two locations within the watershed. Results showed that runoff and sediment loads from the area exhibit a marked seasonal trend and that deforested areas located in the foothill regions of the watershed contribute a disproportionate share of the sediment load to the bay. In years when rainfall distributions are uniformly distributed over the area, the sediment yields may be up to 100 percent higher than years when the rainfall is concentrated in the heavily forested mountainous regions.

Notes: : Water budget studies are essential for water resources and environmental management. In this study, a water budget analysis is presented for the Everglades Agricultural Area (EAA) in South Florida for the period from 1973 to 1991. The EAA is a highly productive irrigation/drainage basin that has a high water table and organic soils. Water quality problems are associated with the drainage discharge from the basin. During dry periods, supplemental water is used for irrigation and in rainy periods excess water with relatively higher phosphorus content is pumped out of the basin to Lake Okeechobee and the Everglades ecosystem. Elevated concentrations of phosphorus in the runoff/drainage that is discharged from the EAA basin have created water quality problems. The mean surface water inflow to the basin was 63,990 ha-m, and the outflow was 131,447 ha-m per year. On the average, supplemental surface water use was 47,411 ha-m, and runoff/drainage was 114,816 ha-m per year. The mean annual basin rainfall was 120.9 cm. A general trend in the decline of the wet season rainfall is observed.

Notes: : Geographic Information Systems (GIS) have been successfully integrated with distributed parameter, single-event, water quality models such as AGNPS (AGricultural NonPoint Source) and ANSWERS (Areal Nonpoint Source Watershed Environmental Response Simulation). These linkages proved to be an effective way to collect, manipulate, visualize, and analyze the input and output date of water quality models. However, for continuous-time, basin large-scale water quality models, collecting and manipulating the input data are more time-consuming and cumbersome due to the method of disaggregation (subdivisions are based on topographic boundaries). SWAT (Soil and Water Assessment Tool), a basin-scale water quality model, was integrated with a GIS to extract input data for modeling a basin. This paper discusses the detailed development of the integration of the SWAT water quality model with GRASS (Geographic Resources Analysis Support System) GIS, along with an application and advantages. The integrated system was applied to simulated a 114 sq. km upper portion of the Seco Creek Basin by subdividing it into 37 subbasins. The average monthly predicted streamflw is in agreement with measured monthly streamflw values.

Notes: . The limited success of command-and-control policies for reducing nonpoint source (NPS) water pollution mandated under the Federal Water Pollution Control Act (FWPCA) has prompted increased interest in economic incentive policies as an alternative control mechanism. A variety of measures have been proposed ranging from fairly minor modifications of existing policies to substantial revisions including watershed-wide polices that rely on economic incentives. While greater use of economic incentive policies, such as environmental bonds and point/nonpoint source trading is being advocated in the reauthorization of the CWA, the expected effects of individual proposals will be modest. The characteristics of NPS pollution, namely uncertainty and asymmetrical information, underscores that there is no single, ideal policy instrument for controlling the many types of agricultural NPS water pollution. Some of the usual incentive-based policies, such as effluent taxes, are not well suited to the task. Individual incentive policies proposed for the reauthorized CWA, such as pollution trading or deposit/refund systems, are not broadly applicable for heterogeneous pollution situations. Economic incentive policies may be appropriate in some cases, and command-and-control policies will be preferable in others and may in fact complement incentive policies.

Notes: : Water quality in eutrophic Lake Tohopekaliga, Florida, improved markedly from 1982 to 1992 as a result of reductions in phosphorus and nitrogen loading to the lake. Annual budgets of water, chloride, phosphorus and nitrogen were constructed for the lake, and indicate it is a sink for phosphorus and a source for nitrogen. Water column concentrations of total phosphorus, soluble reactive phosphorus, total nitrogen, dissolved inorganic nitrogen, and chlorophyll a all declined as external inputs of nutrients decreased. Water column nitrogen: phosphorus ratios have increased, suggesting a probable shift from nitrogen- to phosphorus-limitation. This apparent shift in nutrient limitation status also is supported by comparisons of the mean Trophic State Indices for phosphorus, nitrogen, and chlorophyll a. These improvements in water quality are attributed to the diversion of wastewater treatment plant effluent from the lake, and the increased use of wet retention ponds for stormwater runoff.

Notes: : Concentrations of nitrite plus nitrate, ammonia, orthophosphate, and atrazine were measured in streams and ground water beneath the streams at 23 sites in the South Platte River basin of Colorado, Nebraska, and Wyoming to assess: (1) the role of ground water as a source of nutrients and atrazine to streams in the basin, and (2) the effect of land-use setting on this process. Concentrations of nitrite plus nitrate, ammonia, orthophosphate, and atrazine were higher in ground water than in the overlying streams at 2, 12, 12, and 3 of 19 sites, respectively, where there was not a measurable hydraulic gradient directed from the stream to the ground water. Orthophosphate was the only constituent that had a significantly higher (p ≤ 0.05) concentration in ground water than in surface water for a given land-use setting (range land). Redox conditions in ground water were more important than land-use setting in influencing whether ground water was a source of elevated nitrite plus nitrate concentrations to streams in the basin. The ratios of nitrite plus nitrate in ground water/surface were were significantly lower (p ≤ 0.05) at sites having concentrations of dissolved oxygen in ground water ≤ 0.5 mg/L than at sites having dissolved oxygen concentrations ≥ 0.5 mg/L. Elevated concentrations of ammonia or atrazine in ground water occurred at sites in close proximity to likely sources of ammonia or atrazine, regardless of land-use setting. These results indicate that land-use setting is not the only factor that influences whether ground water is a source of elevated nutrient and atrazine concentrations to streams in the South Platte River Basin.

Notes: : The American Society of Civil Engineers (ASCE) Model State Water Code provides suggested statutory language and commentary helpful in guiding western water law reform. Departing from the past preference for stream diversions and consumptive uses, the code is sensitive to the public's interest in maintaining environmental quality. The traditional doctrine protected inefficient uses and in some states hampered transfers. The model code addresses these issues as well as advocating integrated manage. meat and water resource planning. The debate on how to reform water law has already started, and the model code provides material useful in the reform process. Even with the current draft code, a few gaps exist for later resolution.

Notes: : Due to the spread of Islam in the seventh century the number of pilgrims to the City of Makkah increased sharply, resulting in an acute water shortage. To solve this problem, galleries were built to collect water from the upstream of Wadi Naaman and transfer it to Makkah.Expansion of Makkah and the absence of any mapping of the galleries have resulted in the destruction of a part of the galleries. This caused a discontinuity of flow in the galleries and, consequently, the ground water table is rising at a rate of 0.48 m/yr, causing environmental problems. Research was conducted to rehabilitate the destructed part of the galleries, and to find an appropriate use for the ground water. The study found that the quality of the ground water is suitable for landscaping purposes, that is, for the irrigation of trees and ornamental plants.

Notes: : The Rational Method continues to be the most widely used approach for estimating P-year return frequency peak flow rates for small catchments of about one square mile or less in area. The Balanced Design Storm unit hydrograph method is perhaps the second most widely used technique for estimating peak flow rates (and is the most widely used method for developing runoff hydrographs) but is generally considered to be more accurate than the Rational Method. In this paper, both of these T-year return frequency peak flow rate estimators are shown to be mathematically comparable. The close similarity between these two approximators may help explain why the Rational Method continues to be widely used even though other more computationally sophisticated techniques are readily available due to widespread computer software.

Notes: : The proportionality coefficient, K, and the weighing parameter, X, required for the Muskingum-Cunge Flood Routing Method are dependent on the hydraulic characteristics of the channel and the dynamic characteristic of the flood wave. This work focuses on the determination of the Muskingum-Cunge Flood Routing Method parameters for streams where measured hydrographs are not available (i.e., ungaged streams) with floods that stay within the channel banks. In the present work, a gaged creek was used and a dynamic wave was routed to test the reliability of the parameters determined through the Schaefer and Stevens technique (Schaefer and Stevens, 1978). The predicted outflow hydrographs are compared to the hydrographs obtained for the same stream determined with the Muskingum Routing option of the HEC-1 program. Cypress Creek in Harris County, Texas, was the model for this work; and the corresponding data were extracted from the Grant Road and Westfield, Texas, USGS gaging stations.

Notes: : The unique characteristics of the hydrogeologic system of south Florida (flat topography, sandy soils, high water table, and highly developed canal system) cause significant interactions between ground water and surface water systems. Interaction processes involve infiltration, evapotranspiration (ET), runoff, and exchange of flow (seepage) between streams and aquifers. These interaction processes cannot be accurately simulated by either a surface water model or a ground water model alone because surface water models generally oversimplify ground water movement and ground water models generally oversimplify surface water movement. Estimates of the many components of flow between surface water and ground water (such as recharge and ET) made by the two types of models are often inconsistent. The inconsistencies are the result of differences in the calibration components and the model structures, and can affect the confidence level of the model application. In order to improve model results, a framework for developing a model which integrates a surface water model and a ground water model is presented. Dade County, Florida, is used as an example in developing the concepts of the integrated model. The conceptual model is based on the need to evaluate water supply management options involving the conjunctive use of surface water and groundwater, as well as the evaluation of the impacts of proposed wellfields. The mathematical structure of the integrated model is based on the South Florida Water Management Model (SFWMM) (MacVicar et al., 1984) and A Modular Three-Dimensional Finite-Difference Groundwater Flow Model (MODFLOW) (McDonald and Harbaugh, 1988).

Notes: : Water resources professionals should be engaged actively in revisiting state water rights law. During the past four years, sponsored by the American Society of Civil Engineers with cooperation of other water resources organizations, over a hundred engineers, hydrologists, geographers, lawyers, administrators, educators, water users, and other persons interested in water law have been preparing a Model State Water Rights Code. Preliminary drafts of the Model Code have been considered in four states, and its provisions will be disseminated nationally to state legislators and other policy makers upon formal publication in September 1994. The Model Code gathers the best provisions from state water laws into comprehensive regulated riparian and prior appropriation provisions, includes commentaries explaining how its textual sections address water resources planning and management issues, and references similar language in current state water statutes. The goal of the Code Project is to provide materials which will assist legislators so they can enact effective, efficient, and equitable water laws. In the future, the Code drafting group will expand its efforts to develop legal guidelines for allocating shared transboundary water resources, water quality law, federal water statutes, and other water resources legal issues.

Notes: : Water hyacinth (Eichhornia crassipes L.) has shown to be effective in the treatment of municipal wastewater in a pilot study begun in January 1989 by the Pima County Wastewater Management Department and researchers associated with The University of Arizona's Office of Arid Lands Studies in the Sonoran Desert near Tucson. The influent pumped into the pilot facility's six raceways (ponds) typically has been treated secondary effluent diverted from a conventional treatment facility, although primary effluent from the same facility also has been treated. The Secondary Influent Treatment System has met the Arizona Department of Environmental Quality (ADEQ) tertiary standard for BOD5 and TSS of 10 mg/l for every month of its operation since March 1990; the Primary Influent Treatment System met the ADEQ secondary standard for BOD5 and TSS of 30 mg/1 for most of the 10 months it was in operation.

Notes: : The U.S. Geological Survey (USGS) is assessing the ground-water resources of the carbonate bedrock aquifers in Indiana and Ohio as part of their Regional Aquifer Systems Analysis program. Part of this assessment includes the determination of unknown aspects of the hydraulic characteristics, boundaries, and flow paths of the carbonate aquifer. To accomplish this, the USGS drilled three wells through the carbonate aquifer near the Kankakee River in northwestern Indiana. Geophysical logs were used to help determine depths and thicknesses for testing and to help describe geology at the three wells. Packer tests were used to determine direction of ground-water flow and to provide data for an analysis of the distribution of transmissivity in the carbonate aquifer.Transmissivity of the carbonates is associated with two physical characteristics of the rocks: fractures and interconnected porosity. Almost all of the transmissivity is derived from horizontal fracturing; however, only a few of the fractures present in the carbonate are transmissive. Some transmissivity is associated with a zone of fossiliferous, vuggy dolomite, which yields water from the rock matrix. Most of the transmissivity is associated with large fractures and solution crevices in the upper 30 feet of the bedrock; less transmissivity is associated with the deeper vuggy reef material, even where extensively fractured. Transmissivity of individual fractures and fossiliferous zones ranges from 300 to 27,000 feet squared per day. The aquifer bottom is defined by a lack of transmissive fractures and an increased shale content near the contact of the Silurian and Ordovician sections.Water-level data from the three wells indicate that flow is horizontal at well site 1 north of the Kankakee River, upward at well site 2 near the river, and downward at well site 3 south of the river. Most of the flow occurs in the upper part of the carbonate bedrock where fracturing and solution-enlarged crevices are most developed. Water levels indicate the the Kankakee River is a hydrologic boundary for the regional carbonate bedrock aquifer.

Notes: : This paper describes methods for estimating volume-duration-frequency relations of urban streams in Ohio with drainage areas less than 6.5 square miles. The methods were developed to assist engineers in the design of hydraulic structures on urban streams for which temporary storage of water is an important element of the design criteria. Multiple-regression equations were developed for estimating maximum flood volumes of d-hour duration and T-year recurrence interval (dVT). Maximum annual flood-volume data for all combinations of six durations (1, 2, 4, 8, 16, and 32 hours) and six recurrence intervals (2, 5, 10, 25, 50, and 100 years) were analyzed. The significant explanatory variables in the resulting 36 volume-duration-frequency equations are drainage area, average annual precipitation, and basin-development factor. Standard errors of prediction for the 36 dVT equations range from ±28 percent to ±44 percent.

Notes: : A study of concentrations and distribution of major and trace elements in surficial bottom sediments of Little Rock Lake in northern Wisconsin included examination of spatial variation and grain-size effects. No significant differences with respect to metal distribution in sediments were observed between the two basins of the lake, despite the experimental acidification of one of the basins from pH 6.1 to 4.6. The concentrations of most elements in the lake sediments were generally similar to soil concentrations in the area and were well below sediment quality criteria. Two exceptions were lead and zinc, whose concentrations in July 1990 exceeded the criteria of 50 μg/g and 100 μg/g, respectively, in both littoral and pelagic sediments. Concentrations of some elements, particularly Cu, Pb, and Zn, increased along transects from nearshore to midlake, following a similar gradient of sedimentary organic carbon. In contrast, Mn, Fe, and alkali/alkaline-earth elements were at maximum concentrations in nearshore sediments. These elements are less likely to partition to organic particles, and their distribution is more dependent on mineralogical composition, grain size, and other factors. Element concentrations varied among different sediment grain-size fractions, although a simple inverse relation to grain size was not observed. Fe, Mn, Pb, and Zn were more concentrated in a grain-size range 20–60 tm than in either the very fine or the coarse fractions, possibly because of the aggregation of smaller particles cemented together by organic and Fe/Mn hydrous-oxide coatings.

Notes: : Small systematic changes in climatic records are often poorly visualized by standard time series plots because they are usually hidden by the magnitude and variability of the data values themselves. A visualization approach based on the rescaled adjusted partial sums (RAPS) which overcomes the above-stated shortcomings is presented. This visualization highlights trends, shifts, data clustering, irregular fluctuations, and periodicities in the record. Additional information on the number, magnitude, shape, frequency, and timing of fluctuations and trends can also be inferred. The visualization approach can be used for preliminary visual inspection of a time series, to gain a feel for the data, and/or to guide and focus subsequent statistical tests and analyses. It is not intended as a substitute for standard statistical analysis. Alternatively, the visualization approach can be used to display findings of a time series analysis. The capabilities and limitations of the approach are discussed and illustrated for two time series of annual rainfall values.

Notes: : Methods of computing probabilities of extreme events that affect the design of major engineering structures have been developed for most failure causes, but not for design floods such as the probable maximum flood (PMF). Probabilities for PMF estimates would be useful for economic studies and risk assessments. Reasons for the reluctance of some hydrologists to assign a probability to a PMF are discussed, and alternative methods of assigning a probability are reviewed. Currently, the extrapolation of a frequency curve appears to be the most practical alternative. Using 46 stations in the Mid-Atlantic region, the log-gamma, log-normal, and log-Gumbel distributions were used to estimate PMF probabilities. A 600,000-year return period appears to be a reasonable probability to use for PMFs in the Mid-Atlantic region. The coefficient of skew accounts for much of the variation in computed probabilities.

Notes: : In May 1993, a single-family home and adjoining information center opened to the public at the Desert Botanical Garden in Phoenix, Arizona. Desert House is designed as an example of what can be achieved today using available technology to improve residential water and energy efficiency. The home is expected to reduce water and energy use by 40 percent compared with that for the typical three-bedroom, single-family residence in the Phoenix area. Water-conserving features include: landscape design employing low-water use plants, minimum turf area, mulch around plants to reduce evaporation, and drip irrigation system; spa cover for evaporation reduction; rainwater harvesting; low-flow shower heads, faucets, and toilets; and graywater reuse system. The home will be occupied by a family and monitored for water and energy use by computer. Visitors are able to access real time water and energy use data about the home, as well as tour the information center, technical exhibits, surrounding landscape, and the home when it is open (one afternoon a week).

Notes: : The Basin Characteristics System (BCS) has been developed to quantify characteristics of a drainage basin. The first of four main BCS processing steps creates four geographic information system (GIS) digital maps representing the drainage divide, the drainage network, elevation contours, and the basin length. The drainage divide and basin length are manually digitized from 1:250,000-scale topographic maps. The drainage network is extracted using GIS software from 1:100,000-scale digital line graph data. The elevation contours are generated using GIS software from 1:250,000-scale digital elevation model data. The second and third steps use software developed to assign attributes to specific features in three of the four digital maps and analyze the four maps to quantify 24 morphometric basin characteristics. The fourth step quantifies two climatic characteristics from digitized State maps of precipitation data.Compared to manual methods of measurement, the BCS provides a reduction in the time required to quantify the 26 basin characteristics. Comparison tests indicate the BCS measurements are not significantly different from manual topographic-map measurements for 11 of 12 primary drainage-basin characteristics. Tests indicate the BCS significantly underestimates basin slope. Comparison-measurement differences for basin slope, main channel slope, and basin relief appear to be due to limitations in the digital elevation model data.

Notes: : In this paper, we review recent experience with drought in south Florida, and report some results of a study of the likely agricultural economic impacts of drought. Our conclusions can be summarized as follows. (1) Whether a period of low rainfall becomes a “drought” in south Florida is determined largely by institutional factors. (2) The impacts of a drought event are dependent on the rules the Water Management District uses to manage the event. If the rules involve effective reductions in irrigation supply, the financial impacts may be large, but are sensitive to the way in which cutbacks are imposed. (3) Current drought management regulations do not appear to minimize the short-run cost of drought. (4) Current policies which seek to minimize the short-run cost of drought are inconsistent with dynamically-optimal policies.

Notes: ABSTRACI:. Slash burning is a common site preparation technique used after timber harvest throughout the Southeastern United States. Little quantitative information exists on the hydrologic response to burn severity. This study compared the effects of low-severity and high-severity burns on runoff and sediment yields during rainfall simulation and during natural rainfall in the Southern Appalachian Mountains. Fire severity was largely determined by moisture conditions of the forest floor prior to ignition. Runoff and sediment yield variability was high between plots within the same treatment area due to differences in forest floor characteristics and infiltration rates. Conditions of high-severity resulted when burning was conducted with relatively dry fuels. Sediment yields were 40-times greater for the high-severity treatment areas than the low-severity treatment areas.

Notes: : Application of fertilizer can degrade quality of runoff, particularly during the first post-application, runoff-producing storm. This experiment assessed and compared runoff quality impacts of organic and inorganic fertilizer application for a single simulated storm occurring seven days following application. The organic fertilizers used were poultry (Gallus gallus domesticus) litter, poultry manure, and swine (Sus scrofa domesticus) manure. All fertilizers were applied at an application rate of 217.6 kg N/ha. Simulated rainfall was applied at 50 mm/h for an average duration of 0.8 h. Runoff samples were collected, composited, and analyzed for nitrate N (NO3-N), ammonia N (NH3-N), total Kjeldahl N (TKN), ortho-P (PO4-P), total P (TP), chemical oxygen demand (COD), total suspended solids (TSS), fecal coliforms (FC), and fecal streptococci (FS). Application of the fertilizers did not alter the hydrologic characteristics of the receiving plots relative to the control plots. Concentrations of fertilizer constituents were almost always greater from treated than from control plots and were usually much greater. Flow-weighted mean concentrations of NH3-N, PO4-P, and TP were highest for the inorganic fertilizer treatment (42.0, 26.6, and 27.9 mg/L, respectively). Runoff COD and TSS concentrations were greatest for the poultry litter treatment. Concentrations of FC and FS were greater for fertilized than for control plots with no differences among fertilized plots, but FC concentrations for all treatments were in excess of Arkansas' primary and secondary contact standards. Mass losses of fertilizer constituents were low (≤ 3 kg/ha) and were small proportions (≤ 3 percent) of amounts applied.

Notes: : This paper explores the occurrence of multiple critical depths in one-dimensional computational models of open channel systems. The mathematical formulation is reviewed, including examination of the number of possible roots by Descartes' Rule. Governing equations and dependent variables are scrutinized using two compound cross sections. Occurrence tendencies are reviewed for singular channels. Critical flow is introduced as a tool to determine the existence and location of computationally based multiple critical depths. A strategy to manage multiple critical depths in existing one-dimensional steady or unsteady models is proposed.

Notes: It seems likely that historians in the past have seriously underestimated the number of English townsmen in the early fourteenth century. In London alone there may have been 80–100,000 around 1300. The population of Norwich in the early fourteenth century was higher than used to be thought, and it was growing: Rutledge proposes 17,000 for 1311 and 25,000 for 1333. Keene's estimate of about 10,000 for Winchester in the early fourteenth century can serve as a basis for estimating the population of other towns in the same period. Those whose taxable value in 1334, and whose contribution to the poll tax of 1377, was at least as great as Winchester's, probably had a population equal to Winchester's or greater around 1300. By this argument about fifteen towns, including London, are likely to have had 10,000 or more people at the beginning of the fourteenth century, and perhaps 5 per cent of England's population lived in towns of this rank. Estimates taking account of smaller towns are much more precarious, but it is possible that all told 10 per cent of England's population lived in towns of over 2,000 inhabitants and that a further 5 per cent lived in small boroughs, some with as few as 300 people. Even this estimate does not take account of many small market towns, not described as boroughs, that had elementary urban characteristics.

Notes: What did the public think about public health reform in mid-Victorian Britain? Historians have had a lot to say about the sanitary mentality and actions of the middle class, yet have been strangely silent about the ideas and behaviour of the working class, who were the great majority of the public and the group whose health was mainly in question. Perhaps there is nothing to say. The working class were commonly referred to as ‘the Great Unwashed’, purportedly ignorant and indifferent on matters of personal hygiene, environmental sanitation and hence health. Indeed, the writings of reformers imply that the working class simply did not have a sanitary mentality. However, the views of sanitary campaigners should not be taken at face value. Often propaganda and always one class's perception of another, in the context of the social apartheid in Britain's cities in the mid-nineteenth century, sanitary campaigners' views probably reveal more about middle-class anxieties than the actual social and physical conditions of the poor. None the less many historians still use such material to portray working-class life, but few have gone on to ask how public health reform was seen and experienced ‘from below’. Historians of public health have tended to portray the urban working class as passive victims who were rescued by enlightened middle-class reformers. This seems to be borne out at the political level where, unlike with other popular movements of the 1840s and after, there is little evidence of working-class participation in, or support for, the public health movement.

Notes: For over thirty years demography has featured prominently on the urban history agenda. As long ago as 1963, in an article subtitled ‘On broadening the relevance and scope of urban history’, Eric Lampard emphasized that ‘An autonomous social history ought to begin with a study of population: its changing distribution in time and space’. In 1968 Leo Schnore suggested concentration upon ‘the demographic and ecological aspects of urban life’, according demography the number one priority. Leading British urban historians and historical geographers repeated such injunctions in the 1970s, emphasizing how little was known about even the most basic aspects of pre-industrial urban populations and how far British researchers lagged behind their continental colleagues in the field of urban demography. Unfortunately the response of the last generation of researchers to these precepts has been decidedly muted, and pre-industrial urban demography in England remains in its infancy.

Notes: In spite of the campaigns for social housing conducted by its most ardent supporters, at the beginning of the century Greece completely lacked the various low-cost housing organizations that were quite common in Europe. During the inter-war period, progressive governments took various steps to rationalize the provision of housing, aiming, among others, at encouraging the formation of housing co-operatives. Under the provisions of appropriate legislation, housing cooperatives acquired land on favourable terms either in or outside the city of Athens. The proposed schemes, which were meant to be supported by state funds, were, however, inadequately administered, mainly because of the political instability and economic hardships of the inter-war period. As a result, the function of the housing co-operatives was gradually restricted to providing small investors with cheap land, on which they would build individually at a more convenient time. The happy exceptions to the rule were co-operative housing schemes which owed their implementation to the higher economic and social status of their members.

Notes: Historians have long recognized the central role of debt and credit for producers, retailers and consumers in the later eighteenth and early nineteenth centuries. Against a background characterized by persistent shortages of specie, limited banking facilities and erratic transport mechanisms, the speculative impulse that fed the expanding economy drew sustenance from a proliferation of instruments of private credit — notably bills of exchange, promissory notes, and accommodation bills — which, together with an increase of trade credit to retailers and their customers, served to promote and intertwine the industrial, commercial and consumer revolutions. ‘At any one time any business owed and was owed many goods caught up in the process of exchange’, Julian Hoppit observes of the later decades of the eighteenth century. ‘All businessmen were creditors and all businessmen were debtors.’ As trade and manufacture increased in English towns and cities, extended chains of indebtedness multiplied the economic links both between individual producers, retailers or consumers and among these sectors of the economy. Thus in Lancashire innkeepers were the debtors of maltsters, brewers and wine merchants, but were the creditors of shopkeepers, who in turn extended webs of consumer credit to sawyers and carpenters, artisans typically indebted (in their capacity as producers) to the master builders for whom they laboured in Liverpool's shipyards. Based on personal faith rather than tangible securities, these varied forms of private credit were notoriously unstable. Broad-based financial crises fuelled by the failure of private credit became commonplace in the last three decades of the century, and persistently disrupted economic life into the Victorian period.