Relevance of Dual Frequency Surveying System Tests for Real Time Field Performance

Bernhard Richter, Alastair Green

Abstract:	Precision applications such as precise navigation and surveying demand the position uncertainty to be in the cm or even mm level. Receiver noise will propagate into the coordinates, but to what extent does the pure receiver noise degrade the position accuracy? Surveying institutes publish GPS receiver and antenna tests to give an indication of the expected performance and there are a large number of performance indicators available such as measurement noise, correlation or inter-channel bias – but these indicators are in general, not well understood. A method commonly employed to estimate receiver system performance is the zero baseline test, where two sensors are connected to the same antenna. The standard deviation of the zero baseline phase noise can differ by an order of magnitude simply depending on the different effective measurement bandwidths. The wrong conclusion could then be made that one receiver has significantly lower noise than the other and would therefore perform better as an RTK-rover. The question therefore arising is whether the zero baseline test or other benchmark tests are relevant for the final Real Time field performance of a dual frequency surveying system. This paper explains the definition and design of various test set-ups which give an indication of the true field performance of a dual frequency GPS sensor. Such tests were employed during the development of System 1200, Leica’s new high-performance GPS surveying system. In order to achieve unequalled performance on long baselines, high reliability, high accuracy, excellent multipath mitigation and good tracking capability during vibration or shock, the design of the performance tests played a significant role in the continual improvements of the system as a whole. Many of the generally known tests such as the zero baseline test must always be viewed in the context with other limiting parameters. Narrowing the phase lock loop band width for example would decrease the noise, but at the same time the tracking capability during vibration or shock would be reduced. These and similar problems where the tests are correlated are discussed in detail in this paper and results of the specified tests for Leica System 1200 are presented.
Published in:	Proceedings of the 17th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2004) September 21 - 24, 2004 Long Beach Convention Center Long Beach, CA
Pages:	1367 - 1373
Cite this article:	Richter, Bernhard, Green, Alastair, "Relevance of Dual Frequency Surveying System Tests for Real Time Field Performance," Proceedings of the 17th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2004), Long Beach, CA, September 2004, pp. 1367-1373.
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