A Geodetic Survey Receiver With up to 12 L1 C/A-Code Channels, and 12 L2 Pseudo-P-Code Channels

Timo Allison, Dom Farmer, Gary Lennen, Kreg Martin

Abstract:	High accuracy long baseline determination using signals from the Global Positioning System (GPS) satellites requires use of dual- frequency (Ll, L2) receivers. This enables compensation for ionospheric delays, and is particularly important at the current time due to higher ionospheric activity near the peak of the 11 year sun-spot cycle. For the survey application, squared-L2 channels have been shown to be a very effective low cost and less complex solution for accessing the L2 phase observable. Squared channels also have the advantage of remaining operational when the P-code is encrypted into the classified Y-code (Anti-spoofing, or AS). However, the squaring process halves the wavelength of the received L2 signal and results in a h-cycle ambiguity when attempting to construct the double-differenced L2 phase. This must be accepted as a penalty of squaring. Current DOD policy would seem to indicate that the P-code will be encrypted only during short periods for AS testing. This will be very beneficial to the survey community (and indeed to any user of P-code equipment without the necessary crypto-interface). A new commercial geodetic survey receiver is described which combines parallel squared-L2 channels with a single sequencing L2 P-code correlating channel. The result provides up to ‘t-2 Pseudo-P-code channels which are able to provide full-cycle L2 phase and P-code pseudorange at every survey measurement epoch. The advantages of processing the full-cycle L2 phase include easier resolution of the L2 integer cycle ambiguities over long baselines, and the availability of the wide-lane technique with an effective wavelength of 86 cm (in a squaring receiver without P- code this would be 43 cm). Results are presented which indicate that the L2 Pseudo-P-code channels can provide high quality full-cycle L2 phase measurements for both static and kinematic surveys. Tracking L2 is unaffected by the magnitude of the rate of change of the ionospheric delay.
Published in:	Proceedings of the 3rd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1990) September 19 - 21, 1990 The Broadmoor Hotel Colorado Spring, CO
Pages:	31 - 40
Cite this article:	Allison, Timo, Farmer, Dom, Lennen, Gary, Martin, Kreg, "A Geodetic Survey Receiver With up to 12 L1 C/A-Code Channels, and 12 L2 Pseudo-P-Code Channels," Proceedings of the 3rd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1990), Colorado Spring, CO, September 1990, pp. 31-40.
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