海上保安庁のDGPSの高精度利用 [in Japanese] High Accuracy Utilizing of the MSA's DGPS [in Japanese]
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The MSA (Maritime Safety Agency) is promoting the development of a DGPS (Differential Global Positioning System) service network, which will contribute to improvement of GPS positioning accuracy. Back in December 1995, the MSA established experimental stations in Tsurugizaki in Kanagawa Prefecture and Daiozaki in Mie Prefecture. The MSA's DGPS evaluates errors in the GPS at specified points on a coordinate system on which the DGPS is based. The DGPS then broadcasts information on corrections to the distances between the reference points and all the GPS satellites and the rates of change in them. The resolution of the corrected values and that of the rates of change are ±0.1 m and ±0.001 m/s respectively. The information is updated at two to five seconds intervals. This information was received at points remote from the sending stations, and GPS positioning was performed. As a result of one day experiment standard deviation of positioning was around ±1 m. This value is a little too large compared with the resolution of corrected values. In order to investigate the cause, these errors were arranged on the time base and the way the errors were produced was studied. As a result it was found that the errors were not produced at random but exhibited one-day periodicity in sidereal-time. Though the cause of the periodical errors is unknown, it is possible to estimate errors. So, the error at a time of a day was estimated based on measured values obtained at the same time of the previous day, and correction was made. As a result, the standard deviation was improved to within ±0.5 m. Thus it was found that the use of the DGPS developed by the MSA would achieve a standard deviation of around ±0.5 m for mobile positioning of navigating ships and so on, and of a root mean square of around ±1 cm on average for long-hour positioning of stationary pionts.
- Jour. Japan Soc. Mar. Surv. Tech.
Jour. Japan Soc. Mar. Surv. Tech. 9(1), 33-41, 1997-03-31
Japan Society for Marine Surveys and Technology