Considerations for Sensor Stabilization Using Stand-Alone GPS Velocity and Inertial Measurements

This paper explores the concept of using a high rate (i.e. 100 Hz), high accuracy integrated velocity (i.e. mm accuracy) estimate from stand-alone GPS measurement for sensor stabilization. The velocity algorithm uses GPS LI code measurements at a rate of 2 Hz and LI carrier measurements at 100 Hz. This velocity can be used for heading determination and then for inertial alignment or stabilization of other sensors. The integrated velocity vector accuracy is at the mm level and can be used to provide heading measurements better than 1 deg. This paper addresses several issues such as the velocity propagated position, relation between the velocity error and position error due to sensor lever-arms, timing accuracy of measurement association between various sensors, and a statistical technique to estimate the velocity error on a dynamic platform using two or more GPS antennas. High update rate position estimates, formed using the propagated velocity is shown to improve upon the noise performance of a triple difference technique. A velocity vector alignment technique is compared to a navigation-grade inertial heading alignment over a long lever-arm. A tradeoff discussion illustrates some measurement alignment and integration considerations for a remote sensor. Analysis of these concepts is provided using flight test data collected on April 12, 2006.