Technical Studies

This project is a continuation of the Dongsha bathymetric lidar survey project conducted by the Ministry of Interior. The goal of this project includes the analysis of the satellite tracking station signals quality, developing validation scheme for the stability of the GPS antenna, Dongsha tidal and vertical datum analysis, and producing contour layers for multipurpose use of the bathymetric dataset. The specification from five international agencies on the establishment of satellite tracking stations is collected. GPS and triangulation surveys were performed for examining the Dongsha satellite tracking station. It is revealed that the antenna tilts toward the TSAA. The current position of TNSM has shifted about one centimeter relative to the three surrounding control points, based on the published coordinates. The quality of the GPS signal calculated by the TEQC software was good. A draft assessment model for the satellite tracking station is proposed. The maintenance of Dongsha tracking station buildings is performed, including the structure enforcement and water proof of the roof. Two surveying missions for monitoring the subsidence of Dongsha control points, including the tidal station reference point were conducted. Two regular maintenance of the tidal station were also carried out. Based on the surveying result, no significant subsidence was observed. 511 days tidal data were collected and analyzed. The elevation of different tidal datum is calculated. This project collected and summarized the mapping standards related to IHO S-57, S-100 and S-102. Intervals of 1m, 5m and 10m contours were derived from the Donghsa digital elevation model (DEM). Two conference papers derived from this project were presented. For the future work, it is recommended that the stability analysis scheme for satellite tracking station could be applied to stations in Taiwan, such as YNSM, for comparison and analysis. Control point monitoring, tidal station maintenance and tidal data analysis are the fundamental spatial data infrastructure work, and should be continued. This project discovered that the Dongsha Atoll existed not only with different tidal phases, but also with different tidal ranges. It is suggested that further research on this subject is necessary. The spatial distribution of patch reef could be important for habitat study. The standard working scheme should be studied.