What are the coordinate systems commonly used in photogrammetry?

Coordinate system is divided into plane rectangular coordinate system, polar coordinate system and cylindrical coordinate system.

1, Cartesian coordinate system.

Based on two vertical number axes, the origin (0,0) is set at the intersection of the number axes, and the positive direction and length of the coordinate axes and the included angle between the coordinate axes can be set arbitrarily. The position of a point is represented by an ordered number pair (x, y).

2. Cylindrical coordinate system.

Cylindrical coordinate system is generally a three-dimensional coordinate system, which is mainly composed of a circular plane and a straight line perpendicular to the plane from every point on the plane. The coordinates in this system consist of a point on the plane, the corresponding polar angle and the vertical coordinate (height).

3. Polar coordinate system.

Take a fixed point O (pole) as the center, take any ray (pole axis) on the plane, take a point on the ray as the starting point (pole), and calibrate the point on the plane according to the distance r from the point to the pole and the included angle θ between the point and the pole axis. Usually (r, θ) indicates the position of a point.

Coordinate system:

Coordinate system is a reference system to describe the spatial position (coordinate) of matter, which is realized by defining specific datum and its parameter form. Coordinates are a set of numerical values that describe the position.

According to the dimension of coordinates, they are generally divided into one-dimensional coordinates (highway milestones), two-dimensional coordinates (cartesian plane rectangular coordinates and Gaussian plane rectangular coordinates) and three-dimensional coordinates (geodetic coordinates and spatial rectangular coordinates). In order to describe or determine the position, a coordinate system must be established, and only when the coordinate exists in a coordinate system can it have practical significance and specific position.