ALBERT

Notes: Digital photogrammetry and softcopy workstations have added a new dimension to aerial triangulation, and some of the previously manual procedures are now available in automated form. Also, commercial software packages for automatic aerial triangulation came on to the market in the last decade. In this study, the results of automatic aerial triangulation using four triangulation software packages, Z/I Imaging's MATCH-AT (ISMAT) and ISAT, LH Systems’ MST and VirtuoZo AAT, are presented. For the comparison of the results of the tie point extraction and the bundle block adjustment for triangulation, a sub-block from the Uster block in Switzerland was selected and used. Differences between these software packages are discussed with respect to their functionality and performance in detail. The achieved standard deviation of image coordinates varies between 0·2 and 0·5 pixel for the systems tested. The more signalised control points and check points to be used, the better the σ0 estimate which could be expected. The average number of extracted tie points varied from system to system with respect to the matching method and the resolution of the images used in the programs. The digital aerial triangulation of the Uster sub-block was faster than analytical triangulation and the elapsed time for triangulation of one image using different systems varies between about 0·5 and 6 min. Nevertheless, results also show that automated aerial triangulation is still prone to error in all systems. Image matching produces many blunders, which can only be handled efficiently by using a sophisticated blunder detection procedure, as is available with robust estimation. This is not the case for all the systems tested, however. There still remains a lot to be done in terms of development (improvement of matching, for example, by integrating robust estimation for error detection at an early stage, implementation of on-line triangulation, better internal quality control procedures, more transparent and simple user interfaces and more useful information for the user with better software manuals). However, it was shown that automatic aerial triangulation provides higher redundancy and reliability of results and much more economical photogrammetric practice than ever before.

Notes: This paper is concerned with a new technique (the terrestrial/photogrammetric (TP) technique) for the detection and compensation of systematic height errors in block aerial triangulation. The technique improves the height accuracy of such triangulation by reducing the original bridging distance, using new bands of corrected photogrammetric tie points as height control together with the original bands of the terrestrial (or ground) height control. A number of photogrammetric blocks with different characteristics and configurations have been tested in a comprehensive manner. The tests show that the TP technique gives consistent results over a wide range of circumstances and that it is a most effective, simple and inexpensive method for the compensation of systematic errors.〈section xml:id="abs1-2"〉〈title type="main"〉RésuméCet article relate une technique nouvelle permettant de détecter et de compenser les erreurs altimétriques systématiques dans l'aérotriangulation par blocs: la technique terrestre/photogrammétrique (TP). Cette technique améliore la précision altimétrique de l'aérotriangulation en réduisant la distance de l'aérocheminement original, grâce à l'utilisation d'un canevas de points d'appuis altimétriques composés de points de liaison photogrammétriques corrigés, en supplément du canevas original de points d'appui altimétriques déterminés sur le terrain.On a essayé de manière approfondie un grand nombre de blocs dotés de caractéristiques et de configurations diverses. Les essais montrent que la technique TP fournit des résultats fiables dans un large éventail de circonstances et que c'est une méthode de compensation des erreurs systématiques efficace, simple et peu coûteuse.〈section xml:id="abs1-3"〉〈title type="main"〉ZusammenfassungIm Artikel wird ein neues Verfahren behandelt (das terrestrisch-photogrammetrische Verfahren (TP)), das zur Aufdeckung und Kompensation system-atischer Höhenfehler in der Block triangulation dient. Es wird die Höhengenauigkeit durch Verkürzung der ursprünglichen Überbrückungsdistanz verbessert, indem neue Streifen korrigierter Verbindungspunkte als Höhenpasspunkte zusammen mit den ursprünglichen Reihen der terrestrischen Höhenpasspunkte verwendet werden. Eine Anzahl photogrammetrischer Blöcke unterschiedlicher Figur und Charakteristik wurde umfassend getestet. Die Tests zeigen, dass die TP-Methode konstante Ergebnisse für einen grossen Bereich van Möglichkeiten ergibt und dass es ein höchst effektives, einfaches und billiges Verfahren zur Eliminierung systematischer Fehler ist.