Bundle Adjustment For 35 mm Oblique Aerial Photography

Abstract

The full provision of ground control points for oblique, small format photography used for mapping purposes is uneconomic because each photograph covers a small area of ground. This paper describes the implementation of a bundle adjustment program for 35 mm oblique aerial photography. Image co‐ordinates are measured on enlarged prints, with a digitizing tablet driven by Carto MDSD software, and are then processed with the NLHBUNT program. The measurement system was proved by using vertical standard format photographs of a test block saturated with high quality ground control. Measurements taken with the MDSD system gave acceptable accuracy when compared with a set taken with a Zeiss P3 analytical workstation. A bundle adjustment was then carried out with the MDSD data; the results obtained compared satisfactorily with known ground values. A hand‐held 35 mm Pentax LX camera was flown over the test site and three strips of 1:30 000 scale oblique photography were obtained. Following bundle adjustment, the empirical accuracy of derived co‐ordinates was about 1.5 m in X, 3 m in Y and 2 m in Z. Factors affecting this accuracy are discussed and further developments of the system are proposed.