As the length a line goes on increasing, the error in measurement of distance using EDM repeatedly changes to a maximum and a minimum value non-linearly. This non-linearity of error in measurement is determined by making use of a series of stations placed at precise intervals. The distance between the first and the last point at which reflector has been placed should be at least equivalent to the half wavelength of maximum modulated frequency. Readings are taken from a single instrument setup placing reflectors at successive points. A plot of distance versus correction provides the correction for measurement of distance.

In most EDM, factory calibration is performed so that the average non-linearity and true distance coincide. However, calibration for non-linearity is needed when it is being used for high precision projects.

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