How to calculate error due to curvature and refraction?
Answers
Answer: Error due to curvature comes into play, because in the cases of long distances, the horizontal line and level line do not coincide. Level line is a curved line, parallel to the level surface, but the horizontal lines goes straight.
This means that the vertical distance of that target from the level line is going to be larger than the distance which we calculate from the horizontal line. Please refer the figure given above, the amount of correction depends upon the magnitude of the horizontal distance between the target and the instrument station.
Formula:
Curvature correction, Cc = - 0.07849.D^2 meter
Error to refraction can be understood easily once you understand the phenomenon which takes place when light passes from one density system to another density system. Refraction is nothing but the phenomenon by which when light travels from a denser media to the lighter media, it deflects away from the normal to the plane of the media.
Formula :
Refraction Correction, Cr = 0.01121.D² meter
Combined Correction C = Cc+Cr= -0.06728. D² meter; here D is in kilometer
Explanation: