Providing Highly Accurate Velocity Data for an Airborne Platform Using Differential GPS Velocity Corrections from a Non-Surveyed Reference Receiver

Randal C. Galijan and James Y. Gilkey

Abstract:	This paper presents work performed by SRI International to provide highly accurate, diffetentially corrected velocity data in non-real time for an airborne platform. Radial motion between the platform and satellites (SVs) is derived from Doppler generated by a multi-channel coarse-acquisition (C/A) code GPS receiver from integrated carrier phase measurements. Velocity data are differentially corrected using measurements from a statioiary GPS receiver at a non-surveyed location. Ephemeris data are used to calculate the angles between the platform, reference receiver, and SVs. The differentially corrected velocity data are used to calculate the path of a synthetic aperture radar (SAR) sensor aboard the airborne platform. Absolute location of the sensor in an earth-based coordinate system is not required, but highly accurate data of the sensor's movement along a fairly straight and level flight provide rerequimd to construct a radar image from sensor data. Preliminary indications are that velocity accuracies of a few centimeters per second were achieved in the horizontal and vertical axes. When relative motion is required instead of absolute location, a stationary (hut non-surveyed) reference receiver can be used to provide differential velocity corrections. Using this corQuration it is not necessary to resolve can& phase ambiguities or perform antenna swapping, or for the moving and stationary receivers to maintain continuous lock on a communal set of SVs. The absolute locations of moving and reference receivers are only needed to a certain accuracy to calculate angles.
Published in:	Proceedings of the 1993 National Technical Meeting of The Institute of Navigation January 20 - 22, 1993 Parc 55 Hotel San Francisco, CA
Pages:	103 - 111
Cite this article:	Galijan, Randal C., Gilkey, James Y., "Providing Highly Accurate Velocity Data for an Airborne Platform Using Differential GPS Velocity Corrections from a Non-Surveyed Reference Receiver," Proceedings of the 1993 National Technical Meeting of The Institute of Navigation, San Francisco, CA, January 1993, pp. 103-111.
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