Effects of Exterior Orientation Elements on Direct Georeferencing in POS-Supported Aerial Photogrammetry

Direct georeferencing has become more and more important in aerial photogrammetry, but the accuracy can't satisfy the requirements at small mapping scales in practical projects. The main reason is that the accuracy of exterior orientation elements determined by the POS is not high enough. According to the theory of space intersection and error propagation law, mathematical model of exterior orientation elements' effects on direct georeferencing based on space intersection proposed firstly. Afterwards, mathematical model of exterior orientation elements' effects on direct georeferencing based on collinearity equations are proposed according to collinearity equations and least square adjustment. The mathematical models are experimented using three sets of actual data at different photographic scales and terrains. Based on the empirical results, the effect rules of exterior orientation elements' errors on direct georeferencing in theory and in practice are analyzed respectively. Finally, effects of different combinations of same accuracies of exterior orientation elements on direct Georeferencing are discussed.