Velocity sounding – What is CMP?

September 28 2022

CMP stands for Common Mid-Point, a simple sounding to measure the GPR velocity in the ground or in other materials.

Velocity sounding is a useful way to estimate the velocity of the signal in the subsurface. The two most common methods for velocity sounding are Common Mid-Point (CMP) and Wide Angle Reflection and Refraction (WARR). Note that both these methods require separate transmitter and receiver antennas.

CMP can be carried out with a point or horizontal layer reflector. From a common mid-point, the transmitter and receiver antennas are moved outwards, continuously, or stepwise.

In the resulting radargram you see the following features, where the slope of the reflected wave is used to calculate the velocity:

Velocity sounding – What is CMP?

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