Integer ambiguity resolution in precise point positioning: method comparison |
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| Authors: | Jianghui Geng Xiaolin Meng Alan H Dodson Felix N Teferle |
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| Institution: | (1) Institute of Engineering Surveying and Space Geodesy, The University of Nottingham, Nottingham, NG7 2RD, UK |
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| Abstract: | Integer ambiguity resolution at a single receiver can be implemented by applying improved satellite products where the fractional-cycle
biases (FCBs) have been separated from the integer ambiguities in a network solution. One method to achieve these products
is to estimate the FCBs by averaging the fractional parts of the float ambiguity estimates, and the other is to estimate the
integer-recovery clocks by fixing the undifferenced ambiguities to integers in advance. In this paper, we theoretically prove
the equivalence of the ambiguity-fixed position estimates derived from these two methods by assuming that the FCBs are hardware-dependent
and only they are assimilated into the clocks and ambiguities. To verify this equivalence, we implement both methods in the
Position and Navigation Data Analyst software to process 1 year of GPS data from a global network of about 350 stations. The
mean biases between all daily position estimates derived from these two methods are only 0.2, 0.1 and 0.0 mm, whereas the
standard deviations of all position differences are only 1.3, 0.8 and 2.0 mm for the East, North and Up components, respectively.
Moreover, the differences of the position repeatabilities are below 0.2 mm on average for all three components. The RMS of
the position estimates minus those from the International GNSS Service weekly solutions for the former method differs by below
0.1 mm on average for each component from that for the latter method. Therefore, considering the recognized millimeter-level
precision of current GPS-derived daily positions, these statistics empirically demonstrate the theoretical equivalence of
the ambiguity-fixed position estimates derived from these two methods. In practice, we note that the former method is compatible
with current official clock-generation methods, whereas the latter method is not, but can potentially lead to slightly better
positioning quality. |
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