Strip and block adjustments in aerial triangulation

Abstract

The adjustment of aerial triangulation has been a subject of serious study since aerial triangulation was introducedo In recent years the usage of sophisticated computers has greatly advanced the techniques of adjustments. Many survey departments carry out aerial triangulation for mapping purposes only. Thus when adjustments are applied and accuracies specified, they are related to mapping at various scales. In this thesis, the author carried out aerial triangulation by independent models on wild A8. The original purpose for the photography was mapping for cadastral purposes at the scale of 1/2500. The photography covers an agricultural area.

The author has concentrated on the problem of transformation of machine strip coordinates into the ground system, and the subsequent adjustments. Some transformation and adjustment methods which had been recommended by L.P. Adams (10) have been modified. The relationship between long and short strips were investigated and the usefulness of Helmert's Transformation in-strip and Block transformation was investigated. An attempt was also made in the transformation of plan and height values simultaneouslyo This transformation was done on _an ICL 1900 computer, but all the other computations were done on Hewlett Packard Calculator. The author has also introduced and indicated the possibilities of using distribution-free statistical analysis. All the recommendations and conclusions arrived at are directed to the)prOblems of adjustment of aerial triangulation for mapping purposes, The data used consisted of the following: Block •••••••••••••••• Mathira, Ndia, South Tetu (Kenya) Contract ••••••••••••• 65.24 Purposes ••••••••••••• Cadastral Mapping Scale of Photography ••••• 1/12,500 Organization •••••••••••••• Survey of Kenya Date ••••••••••••••••• 1965 Flying Height ••••••• 7,500 ft. above Terrain )Camera •••••••••••••• Wild R.C. 8 Lens •••••••••••••••• Wild Aviogon F. 5.6 Calibrated Principal Distance ••••• 152.06 mm Fore and A~ Overlap ••••••••••• 60% Lateral Overlap •••••••••••••••• 28% Navigatio~ and Stabilisation •••••••••• Nil -Auxiliary Instruments •••••••••••••••• Nil Number of Strips ••••••••••••••••••••• 4 (4, 5, 6, 7) Average Number of Models •••••••••••••• 19

Although the purpose of mapping was for cadastral mapping, the survey is only tertiary and fourth order in accuracy_ It is supposed to provide base maps for land adjudication and consolidation, and also to provide Registry Index Maps, which indicate consolidated plot boundaries at scales of 1/2500. here Registry Index Maps are required, contours are not necessary and heights should be only sufficiently accurate to ensure adequate levelling of the stereo models. Topographic mapping is also done from such photography. The problem should therefore be considered as restricted to small section cadastral mapping to provide land titles to land owners. The computational problems should as well be considered as those of a small survey office, hence the extensive use of small desk computers.