Guidance: Spatial data acquisition is the first task to be carried out in the construction of geographic information system, which can be implemented in a variety of ways including data conversion, remote sensing data processing, digital measurement, etc, the digital input of existing maps is the most widely used means and the most human resource-consuming work. In GIS, the content entered includes spatial information and non-spatial information, the former is the subject of the entry. At present, there are two main ways to input spatial information, namely, hand-held tracking digitization and scanning vectorization, this chapter introduces two methods and related algorithms, such as curve approximation fitting, raster pattern refinement tracking, etc.

After the input of graphics data, various kinds of processing are needed, including coordinate transformation, stitching, etc. In the topology establishment process, various errors need to be modified first, this chapter describes various specific error scenarios, the polygon automatic topology generation algorithm is introduced finally.