5.3 Attitude of Platform

The geometric distortion depends on not only the geometry of the sensor but also the attitude of the platform. Therefore it is very important to measure the attitude of the platform for the consequent geometric correction.

The attitude of the platform is classified by the following two components.

a. Rotation angles around the three axes ; roll, pitch and yaw b. Jitter ; random and unsystematic vibration which cannot be measured.

The rotation angles ; roll (), pitch () and yaw () are defined as the rotation angles around the flight direction, the main wing and the vertical line respectively, as shown in Figure 5.3.1. Figure 5.3.2 show the satellite attitude parameters.

For a frame camera, the rotation angles are single values common to a full scene of aerial photograph, while for a line scanner the attitude changes as a function of line number or time. In the case of satellites, the variation of the position and the attitude will be continuous, though in case of aircraft, the variation will not always be smooth, which makes the geometric correction more difficult.

The typical attitude sensors for aircraft are as follows.

- Speedometer
- altimeter
- gyro compass (for attitude measurement)
- Doppler radar (for measurement of altitude)
- GPS (for positioning )
- gyro horizon
- TV camera
- flight recorder

The attitude sensors for satellites are introduced in section 5.4.


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