中山站至A冰穹考察及沿线GPS复测结果分析

南极中山站至A冰穹（Dome-A)考察沿线布设有GPS等精度定位点，通过用高精GPS静态定位处理软件GAMIT／GLOBK对三期观测数据的处理可知，考察沿线的GPS点以8－25m/a的速度向西北方向（冰盖边缘方向）流动，越接近冰盖边缘，运动速度赵快，最快达到100m/a；而且冰川整体上以1－5m/^2的加速度流动。同时，由冰盖的流动，引起了垂直方向0－2－1m/a的沉降速度。

Antarctic Traverses from Zhongshan Station to Dome-A and the Results Analysis for the GPS Points along the Expedition Route

The traverse route from Zhongshan station to Dome-A is one of the most important expedition routes of the ITASE (International Trans-Antarctic Scientific Expedition) project.China had carried out her 3 inland traverses during the 1996/1997,1997/1998,1998/1999 Antarctic summer seasons,and pushed forwarded to 300 km,500 km and 1 100 km far away from Zhongshan station respectively.The 3rd scientific traverse team arrived successfully to Dome-A zone on Jan.8,1999.It's the first time for mankind to this zone. 　　In order to develop the ice dynamics to study the mass balance,the ice velocity,etc.,some GPS points with the interval of 30 to 50 kilometers were set up and occupied and reoccupied along the traverse route.The GPS data were collected by the dual-frequency geodetic GPS receivers such as WILD 300,GEOTRACER 3220 GPS receiver,etc.A same type of GPS receiver was set up at Zhongshan station synchronously.At the same time,the GPS data of the Australian Davis station or Mawson station could be downloaded from the AUSLIG (Australian Surveying and Land Information Group) ftp server by anonymous ftp.Thus,the coordinates of the rover GPS points along the traverse route could be achieved from the fiducial sites of Zhongshan station and Davis station or Mawson station.Due to the long-term data collection,which is about 10 hours,the precise ephemeris (SP3 file from the IGS) and the precise coordinates of fiducial sites from the bulletin of IGS were included,and the cm- even mm-level coordinates concerning the rover GPS points can be easily gotten.Thus,the ice flow velocity could be available by comparing the coordinates between the different stages of the same point. 　　There are 7 GPS points named LT980,LT940,LT918,DT008,DT038,DT063 and DT085 respectively on the first 500 kilometers route.The most popular high-accuracy GPS static processing software,GAMIT/GLOBK,was utilized to analyze the sedimentation rate,that is to say,the vertical flow velocity of the above 7 points with the three different epochs 1998.1169，1999.0754 and 1999.9879,as well as the horizontal flow velocity. 　　The results analysis for the GPS data processing was presented in this paper.It indicated that the ice along the traverse route flowed with an 8～25 m/a velocity to the northwest in the last 3 years.Moreover,the nearer it is to the edge of the ice sheet,the faster the flow is.The maximum horizontal flow velocity is about 100m/a.Moreover,due to the ice flow,a 0.2～1 m/a sedimentation rate is achieved.Finally,a 1～5 m/a2 horizontal acceleration was achieved from the 3 different stages' GPS data. 　　Due to no repeating GPS data,the ice flow velocity of the other 18 GPS points along the last 600 kilometers traverse route couldn't be available.Moreover,due to no GPS points was set up on the first 90 kilometers along the traverse route,ice flow information of this route was not available.It is suggested that all of the GPS points be re-occupied and additional 4 to 7 GPS points be interpolated averagely along the first 90 kilometers traverse route in the future traverses.