Assessing the stability of the new marine DGPS station of Hong Kong and its connection to the WGS84 datum

Abstract

The permanent DGPS station of Marine Department, located on Kau Yi Chau Island in Hong Kong, has begun its operation in 1996. One of the factors which affects the quality of the differential corrections generated by the station is the accuracy of its reference coordinates in the WGS84 datum. Although the station is positioned over one of the existing trigonometric stations of Hong Kong datum whose position is also known in the WGS84 datum, the accuracy of the known coordinates needs to be verified independently. We have used two months data to calculate repeated baselines from this station to five IGS core stations located in China, namely, Wuhan, Shanghai, Xian, Lhasa, and Taiwan using the GAMIT software. Sub-centimeter rms baseline error has been demonstrated during this period. These results indicate stability of GPS measurements over a long period of time well beyond expectations. We have used the estimated baseline vectors to connect Kau Yi Chau station to the ITRF94 and subsequently to the WGS84 datum. Preliminary results indicate centimeter and decimeter level agreement in latitude and longitude between the known reference coordinates and the ones derived from ITRF-94 connection. We have observed, however, over three meters of discrepancy in height.