The "projection transformation" of the basic concept of GIS-a brief discussion

Directory

1, overview

Overview

　　Because GIS describes information that is located on the Earth's surface, it can be used as a reference system for spatial data based on the geographic coordinates (GRATICULES) established by the Earth's ellipsoid. And the earth is an irregular sphere, in order to be able to display the content of its surface on the plane of the display or paper, the spherical geographic coordinate system must be transformed into a planar projection coordinate system (Figure 4.1)

The common projection methods are:

• Positive solution transformation: By establishing a close or approximate analytic relationship of projection transformation to another projection, the coordinate x and y of a projection are transformed directly from the digitized coordinates x and y to another projection.
• Inverse transformation: That is, by a projection of the coordinates of the geographical coordinates (x, Y→b, L), and then the geographical coordinates into another projection of the coordinate formula (B, L→x, y), so as to achieve from one projection of the coordinates to another projection coordinate transformation (x, Y→x, y).
• Numerical transformation: According to the two digitized points of the same name in the transformation region, using interpolation method, or finite difference method, least squares, or finite element method, or undetermined coefficient method, so as to realize the transformation from one projection coordinate to another.

The normal solution transformation method is used.

The "projection transformation" of the basic concept of GIS-a brief discussion