GPR Concepts
RD1500 Operation Manual 34 ยฉ Radiodetection 2016
Hyperbolas are best viewed when subsurface targets are crossed perpendicularly or at a 90
degree angle. The actual position of the object is located at the apex of the hyperbola.
7.3 Calculating Depth
Ground penetrating radar records the time it takes a radio wave to travel to a target and
back; it does not measure the depth to that target directly. Depth to target is calculated
based on the velocity with which the wave travels to the target and back.
To calculate depth:
๐ท = ๐ ๐ฅ ๐/2
๐โ๐๐๐ ๐ท ๐๐ ๐ท๐๐๐กโ
๐ ๐๐ ๐๐๐๐๐๐๐ก๐ฆ
๐ ๐๐ ๐กโ๐ ๐๐ค๐ โ ๐ค๐๐ฆ ๐ก๐๐๐ฃ๐๐ ๐ก๐๐๐
For the RD1500, velocity is indicated by the Soil Calibration Value, known as Soil Cal. Once
the Soil Cal values are set, the measured depths will be determined accurately (Section
8.6.6)
7.4 Soil Calibration values
Below is a table of common subsurface materials and their corresponding Soil Cal. This is only
a guideline and there is some variation based on the fact that there can be a mixture of different
materials in the subsurface. The soil water content has the biggest influence, by far, on Soil Cal
values.
Apex of hyperbola is where
the object is located
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