Investigation of physical sensor models for modelling SPOT 3 orbits

This paper investigates the feasibility of modelling entire image strips, instead of individual scenes, that have been acquired from the same orbital pass through bundle adjustments. The focus differs from previous researches in the following aspects: firstly, in modelling image strips when control points are available only on a small portion of the strips and, secondly, in comparing the performance of two types of physical sensor models with various sets of adjustment parameters. The models tested were based on modified collinear equations and on satellite orbit and attitude. For each model seven adjustment parameter sets were defined and checked against two SPOT 3 strips of 420 km in length. Results showed that the accuracy of orbit modelling is highly dependent on the choice of parameters to be adjusted. Models with high-order parameters showed exponential error patterns whereas models with low-order parameters showed linear error patterns. Among the two types of sensor models, those based on satellite orbit and attitude yielded better orbit modelling performance. In particular, the best performance was achieved by the model that adjusts attitude biases only; a nearly constant accuracy of better than 2 pixels was maintained over the whole orbital segment of 420 km. This supports the feasibility of orbit modelling.