Surveying - Engineering

Q1:

Horizontal distances obtained tacheometerically are corrected for

A slope correction

B temperature correction

C refraction and curvature correction

D all the above.

ANS:C - refraction and curvature correction

People saying temperature correction, I want to ask them where they do apply this correction, correction to the ray of light?

Because in tachometer we do not measure distance by any physical means the correction applied to the light ray is curvature and refraction, also known as Cc&Cr.