Development of an Accurate and Low Cost GPS-Based Heading Determination System

Principal Investigator:

Demoz Gebre-Egziabher, Professor, Aerospace Engineering & Mechanics

Project Summary:

Heading is defined as the angle measured from north to a vehicle's longitudinal axis (the axis aligned with the direction of travel). This work explored the development and testing of a GPS-based attitude and heading determination system (AHRS) using single-frequency (L1) carrier-phase differential GPS (CPDGPS). A vehicle's attitude can be uniquely determined from two non-collinear relative-position vectors, known as the baseline vectors. The accuracy of the resulting attitude estimate depends on the accuracy of the baseline vector estimates and their respective magnitudes (length). The shorter the baseline, the higher the vector accuracy required to give the same attitude accuracy that can be obtained through a longer baseline system. Issues such as ambiguity resolution and phase center variations are discussed in the research findings. Test results show that single-frequency CPDGPS is still a challenge, caused primarily by the integer ambiguity problem inherent to CPDGPS. A more feasible but less accurate method using a short baseline is also included in the results. Phase center calibration remains a challenge for this attitude determination system.

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