4:15 PM - 4:30 PM
[SCG56-22] DOP-based accuracy evaluation of GNSS-A positioning on a drifting moored buoy quantified using sea trial observation data
Keywords:GNSS-A measurement, Moored buoy, DOP
To interpret the accuracy degradation and directivity in relation to the position of observing points, we introduced Dilution of Precision (DOP: Langley, 1999) for GNSS-A positioning, which represents the degree of propagation of measurement errors to positioning errors. We firstly calculated EDOP/NDOP (the degree of error propagation to the EW/NS components of the array position) from the diagonal elements of the normal equation matrix of the observation equation of array positioning. Next, we computed error ellipses by diagonalizing the normal equation matrix because the nondiagonal elements were significantly large in many cases. The error ellipses clearly exhibit the feature that the estimation error of array positions was large in the direction from an observing point to the array center. Then, we converted the error ellipses to the positioning accuracy by multiplying the standard deviation of traveltime residuals when an array position was estimated using the data of all the 527 pings. The resulting positioning accuracy well explained the array position error and its dependency on the observing position found in the results of the sea trial.
The DOP analysis and its conversion into the positioning accuracy based on the actual observation data enable detailed assessment of the directional accuracy of GNSS-A positioning at arbitrary observing point, which is quite important in interpreting a realtime measurement of seafloor movement upon the occurrence of a huge earthquake. In this presentation, we will explain the above method and discuss its application to realtime GNSS-A positioning using the system assuming the occurrence of a huge earthquake.
Acknowledgements: This study was supported by MEXT project for Development of GPS/Acoustic Technique, JST Cross-ministerial Strategic Innovation Promotion Program (SIP, Reinforcement of resilient function for preventing and mitigating disasters) and MEXT/JSPS Research Project for compound disaster mitigation on the great earthquakes and tsunamis around the Nankai Trough region.