The completion of the foundation buried stone heads, four measurements, a flat wire measurement, substandard level of measurement, map the root control field data collection and data editing.
The biggest difficulties in gravimetric observations are to get a first class map and the exact location of every measurement.
重力测量中最大的困难就是取得高精度的地形图以及确定每一测点的精确位置。
3
The data of GIS include space data and property data. Position errors are mainly from errors of direct measurement, digitalization of map, data input and store.