Rapid and precise solution of the whole network of thousands of stations in China based on PPP network solution by UPD fixed technology
WANG Hu, DANG Yamin, HOU Yangfei, BEI Jinzhong, WANG Jiexian, BAI Guixia, CHENG Yingyan, ZHANG Shoujian
2020, 49(3):
278-291.
doi:10.11947/j.AGCS.2020.20190326
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Based on the PPP network solution by UPD (uncalibrated phase delay) ambiguity fixed technology, millimeter-level regional differential positioning without a base station and whole network disposable rapid precise solution can be achieved using GNSS data from the first phase of the National Datum Engineering of China and thousands of national CORS stations in each province or municipality.This is of great practical significance to enhance the ability of national survey to meet the urgent need, to realize the rapid establishment of benchmark in the disaster area and to quickly reconstruct the national unified coordinate frame and its service. Firstly, the UPD of wide-lane and narrow-lane are estimated using national GNSS data of 198 continuously operating reference stations during August in 2015. Then, the float carrier phase ambiguities from each GNSS station are fixed using the UPD of wide-lane and narrow-lane until those from all the GNSS stations are completed. The results indicate that there are 193 stations where average successfully fixed rate of wide-lane ambiguities is above 80% and 165 stations where that of narrow-lane ambiguities is above 60%. In addition, the root mean square of whole network solution in North, East and Up direction are 2.8, 3.9 and 5.3 mm, respectively; the standard deviation of whole network solution in North, East and Up direction are 2.1, 3.2 and 6.7 mm, respectively. Compared with single day solutions by SOPAC under the ITRF2008, the external errors in horizontal and vertical direction are both at millimeter level. Finally, we can obtain the accurately phase observations without ambiguities, which are fixed using the UPD of wide-lane and narrow-lane, from 1195 GNSS stations during August in 2015. The whole network disposable solution covering thousands of stations can be achieved using the accurately phase observations without ambiguities, which could reduce the number of ambiguity parameters and overcome the restriction of network in size and the number of stations. The double-difference monthly solution by GAMIT/GLOBK are used to validate the results by the above method. 99.92%, 99.33% and 79.83% stations share a difference of less than 1 cm in North, East and Up direction, respectively. Wherein, the Up-component difference of 93.22% stations are within 1.5 cm. In summary, the accuracy and efficiency of both regional precise positioning without a base station and rapidly calculating for GNSS huge network could be ensured based on the PPP network solution by UPD ambiguity fixed technology. Furthermore, it can also meet the urgent demand to fast reconstruct national coordinate frame and that in disaster area.
