HR: 1340h
AN: G43A-0917    [Abstracts]
TI: Numerical Simulation of Positioning Errors due to Tropospheric Delay- a Case Study With the Japanese GPS Network (GEONET)
AU: * MUNEKANE, H
EM: munekane@gsi.go.jp
AF: Geographical Survey Institute, 1 Kitasato, Tsukuba, 3050811, Japan
AU: KUROISHI, Y
EM: yuki@gsi.go.jp
AF: Geographical Survey Institute, 1 Kitasato, Tsukuba, 3050811, Japan
AU: HATANAKA, Y
EM: hata@gsi.go.jp
AF: Geographical Survey Institute, 1 Kitasato, Tsukuba, 3050811, Japan
AU: YARAI, H
EM: yarai@gsi.go.jp
AF: Geographical Survey Institute, 1 Kitasato, Tsukuba, 3050811, Japan
AB: In this study, we evaluate positioning errors due to tropospheric delay in the coordinate time series of GPS stations in the Japanese GPS network (GEONET) through numerical simulation and investigate their dependence on analysis software and strategies. For this purpose, we have developed simulation software to reproduce GPS observations under certain weather conditions. The software take numerical weather models as input, calculate tropospheric delays using the ray tracing method, and output simulated GPS observations in the RINEX format which are ready for analysis with general GPS analysis software. Here, we first demonstrate the ability of the simulation software by reproducing daily variations of observed positioning errors under severe weather conditions. Then we investigate the characteristics of long-term positioning errors due to tropospheric delays and their dependence on analysis software and strategies. First, we simulated the GPS observations at 71 points in and around Izu peninsula, central Japan from August 29 to September 2 in 2004 when we observed large positioning errors that are coincidental with bad weather conditions due to the combination of the weather front and the typhoon. We used tailored fine-scale numerical weather models which have spatial resolutions of 2km as input. We preliminary analyzed the simulated and observed GPS data with the GIPSY-OASIS software under the same analysis strategy (precise point positioning; NMF mapping function). As a result, we successfully reproduced the daily variations of the directions of observed horizontal errors as well as the patterns of observed vertical errors. This result shows the ability of the software to reproduce the realistic positioning errors of tropospheric origin. Then we investigated long-term positioning errors. We tentatively simulated the GPS observations at 101 points which are more or less evenly-spaced throughout Japan for 2004. We used the meso-scale objective analysis from the Japanese Meteorological Agency (JMA) with spatial resolutions of 10km as input. We analyzed the simulated and observed GPS data with the GIPSY-OASIS software under the same analysis strategy with the former case. As a result, we found clear spatial pattern in the annual signal in the simulated vertical time series. The annual amplitudes gradually increase toward north, reaching 4mm in the northern Japan. The phases are generally homogeneous, taking maximum at around DOY 240. This pattern is recognizable in the observed vertical time series as well, confirming that there still remain considerable unmodelled biases in the GEONET time series on the annual time scale. In this presentation, we will also discuss the spectrum characteristics of troposphere-related positioning errors as well as these seasonal characteristics. Then we will compare the time series obtained with different analysis software and strategy to investigate the dependence of these characteristics on analysis software and strategies.
DE: 1240 Satellite geodesy: results (6929, 7215, 7230, 7240)
DE: 1241 Satellite geodesy: technical issues (6994, 7969)
SC: Geodesy [G]
MN: 2007 Fall Meeting