Principle of EDM

Let the distance between P and Q be “D” which is to be measured.

Wave is transmitted from the transmitter at station P which certain phase angle. This is reflector at the other end Q reflector consist of prism. The wave strike on reflector at Q and then gets reflected from Q. It is received back at the transmitter end at P with difference phase angle. For finding the distance the phase difference between transmitted wave and reflected wave is measured and converted into distance.

Advantages of EDM

1) Measurement of horizontal distance precisely.

2) Measurement of vertical distance more accurately.

3) Measurement in rough and accurate modes.

4) Measurement of N and E co-ordinate.

5) Measurement of inclined distance on slope.