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TIPS: Common Mid-Point GPR surveys using the DVL-500P

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ne of the advanced surveys that can be conducted with a bi-static GPR system like the pulseEKKO (see accompanying story), is a Common Mid-Point survey. A CMP survey provides a simple way of measuring GPR velocity in the ground or other material; critical information for determining the depth of a target.

The velocity measurement relies on incrementally changing the antenna separation to increase the signal path length from the GPR transmitter to the GPR receiver over a mid-point reflector. For accurate velocities, CMP surveys are best performed in an area with one or more horizontal reflectors.

pulesEKKO GPR Map View
pulesEKKO GPR Map View
Figure 1:
pulseEKKO CMP survey using the bi-static pulseEKKO GPR system

The new pulseEKKO DVL 500P contains a number of features to make collecting CMP surveys quick and efficient.

  • The new, customizable System Configuration menu allows users set up and save hardware and survey parameters for specific surveys. If you frequently collect CMP data, creating a System Configuration for your CMP surveys is a good idea.
  • The Start Offset Position setting defines the location of the center point of the CMP survey. If you are collecting a CMP along a previously-collected reflection line, the Start Offset Position can be set to the position on the reflection line. In the example in Figure 1, this position is 25 meters. This makes comparing the CMP analysis results to the reflection line much easier.
  • During data collection, the Transmitter & Receiver positions are indicated relative to the Start Offset Position; making it much easier to position the transmitter and receiver at the correct position along the tape before collecting the next trace.
  • Once the CMP survey is complete, users can take advantage of the DVL-500P’s display capabilities to perform a preliminary analysis of the move out velocities at different times using the Hyperbola Velocity Calibration tool.
new pulseEKKO GPR DVL 500P user interface
Figure 2:
new pulseEKKO GPR DVL 500P user interface

Export the data to a PC and used the CMP Analysis function in the of the EKKO_Project software for further analysis (Processing module required).

Analyze velocity in the field
Figure 3:
Analyze velocity in the field
Perform CMP analysis easily in EKKO_Project
Figure 4:
Perform CMP analysis easily in EKKO_Project

Click here to learn more about pulseEKKO Ground Penetrating Radar.

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