Tape correction (surveying)

In surveying, tape correction(s) refer(s) to correcting measurements for the effect of slope angle, expansion or contraction due to temperture, and the tape's sag, which varies with the applied tension. Not correcting for these effects gives rise to systematic errors, i.e. effects which act in a predictable manner and therefore can be corrected by mathematical methods.

Cv=2Lsin^2(£/2)

Where

When distances are measured along the slope, the equivalent horizontal distance may be determined by applying a slope correction.

The vertical slope angle of the length measured must be measured. (Refer to the figure on the other side) Thus,

Where:

The correction ${\displaystyle C_{h}}$ is subtracted from ${\displaystyle s}$ to obtain the equivalent horizontal distance on the slope line:

When measuring or laying out distances, the standard temperature of the tape and the temperature of the tape at time of measurement are usually different. A difference in temperature will cause the tape to lengthen or shorten, so the measurement taken will not be exactly correct. A correction can be applied to the measured length to obtain the correct length.

The correction of the tape length due to change in temperature is given by:

Where:

The correction ${\displaystyle C_{t}}$ is added to ${\displaystyle L}$ to obtain the corrected distance:

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