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The second step acquires the wide-offset reflection (WOR) data. These profiles are denoted as WOR profiles because the offset between the antennas is much wider than is usually used in standard GPR reflection profiles. The method uses an optimal antenna separation derived from CMP surveys to reliably identify the air wave and the direct ground arrival times.

Wide Offset Reflection Acquisition

Optimal offset (3.5 m)

Transmitter

Receiver

FIGURE 23.3 Acquisition geometry for the wide-offset reflection (WOR) profiles. The transmitter antenna is held stationary and the receiver antenna is moved away at 0.1 m increments until the optimum offset is obtained. This stage is the walkaway stage. The antennas are then moved together in 0.25 m increments across the profile.

Transmitter

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