Sheridan, Kevin Francis; (2001) GPS based position and attitude determination for airborne remote sensing. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

The design and testing of a system to determine the position and attitude of an airborne sensor from GPS observations are described. Using GPS data from a fixed array of four antennas, each connected to an independent receiver, all six exterior orientation parameters of an airborne scanner can be determined with an accuracy that meets the georeferencing requirements for a range of applications. Airborne data collected in two flight trials have been processed using software developed during this research project, and a number of previous studies, to determine a best estimate of the aircraft trajectory. The position and attitude determination algorithms both employ single epoch ambiguity resolution. Attitude is determined directly from GPS measurements, without explicitly estimating relative antenna positions. This increases the redundancy in the solution and hence improves the reliability and robustness of the system. Attitude values derived from GPS data have been integrated with attitude data from a gyro to improve the efficiency of the ambiguity resolution process. A Kalman filter is used to obtain an optimal estimate of the trajectory by integrating all available data and generating orientation values for each scan line. Initially the subjects of georeferencing and GPS based attitude determination are introduced. Trends within georeferencing are discussed, particularly the development of systems that directly measure the position and attitude of airborne sensors using on-board instruments. This provides the context for the specific experimental system developed in the course of this work. The direct georeferencing system is described in terms of the instrumentation and processing methodology employed. Results show that the system is capable of positioning accuracies of 5 to 10mm in plan, and 10 to 30mm in height. It determines attitude with an accuracy of 7 arc minutes in pitch, 20 arc minutes in roll, and 3 arc minutes in heading. At a nominal flying height of 600m this leads to an 'on-the-ground' positioning accuracy of below 4m. By comparing this performance to application and sensor accuracy requirements, the suitability of the georeferencing system can be evaluated.

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