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: Following the installation of the Wildmap digital mapping system, B.K.S. Surveys Ltd. has successfully completed a number of digital mapping projects in Europe, the Middle East and the United States. As a result of experience gained through meeting clients’requirements, carrying out market research and making in house developments the company has updated its original conceptual approach to digital mapping to meet current demands for a land information system. At present B.K.S. is involved in creating a database that is composed of utility, cadastral and topographical data designed for both graphical output and digital processing for resource planning.

Notes: The development and operation of a remote control system for a camera rig and for the camera attached to it are described. Now there is the possibility of reducing the crew from three to two for many tasks and to use the extra payload to collect contemporaneous data using a second airborne system.

Notes: In spite of the striking progress in block adjustment techniques, it is widely assumed that their application continues to be out of reach for a large part of the photogrammetric community that cannot afford expensive computer systems. The COBLO program performs rigorous block adjustment with models and can be implemented even on inexpensive microcomputers. The first COBLO versions are in operation in several places in South America and Europe and the latest versions, which are considerably more efficient, are now being introduced. This paper describes the main features of different COBLO versions and presents the experience of some users.