Before revision: Thus, the correction is subtracted from to obtain the corrected distance: Note that the weight of the tape per unit length is equal to the weight of the tape divided by the length of the tape: so: Therefore, we can rewrite the formula for correction due to sag as:
After revision: Please observe that is not the weight of the complete tape, but of the section between its supports, making this formulation less useful.Thus, the correction is subtracted from to obtain the corrected distance: Note that the weight of the tape per unit length is equal to the weight of the tape divided by the length of the tape: so: Therefore, we can rewrite the formula for correction due to sag as: