Differential GPS: Efficient Tool in Photogrammetry

In the photogrammetric mapping process, a reduction of the amount of ground control can be realized when the position of the aerial camera, or to be more precise the position of its projection center, is determined during the flight. In this paper the results of a testflight performed to investigate the use of differential GPS for this position determination are discussed. From a testfield with extensive ground control, 360 photographs were taken in twelve different strips. Using two different photogrammetric block‐adjustment methods, the coordinates of the projection centers were determined for two different block‐configurations. The estimated accuracies for these coordinates vary between 5 and 10 cm. During the flight these coordinates are also measured with Sercel GPS receivers in a differential mode. Based on a comparison of both results a 10 cm accuracy for the GPS positions is demonstrated within each strip.