Angle measurement must be calibrated to calculate angle measurement.
Calibration is necessary as it compensates for any tilt of the photo image to the right or to the left.
A physical support on the image can be used as calibration reference, provided that it is orthogonal to the line of gravity.
Calibration is performed by clicking two reference points that must be orthogonal to the line of gravity; the two points must be either on a horizontal or vertical plane.
Example of calibration performed on two points on a horizontal plane.
In the example above, the reference is a horizontal support and the calibration indicates -0.2°.
This means that, assuming that the horizontal support is perfectly level, the image is tilted to the left by 0.2°.
Positive values and negative values
Negative values indicate that the tilt is to the left, positive values indicate that the tilt is to the right.
See also:
Manual GPS 5, version 1.0.5 release date:14-01-2011 Copyright © 2011 Chinesport