Guidance: As described in the previous chapter, an element must be embedded in a spatial reference system. Because the information described by GIS is located on the earth’s surface, the geographic coordinates (longitude and latitude network) based on the ellipsoid of the earth can be used as a reference system for all elements. Because the earth is an irregular sphere, in order to display the contents of its surface on a flat display or paper surface, coordinate transformation is necessary.
This chapter describes the ellipsoid parameters and common projection types. Considering that more than 1:1 million topographic maps currently used are all based on Gauss-Kruger projection, this chapter finally gives a brief introduction to this projection type and related topographic map division standards.