User's Manual

5-Data Collection Mode pulseEKKO PRO
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5.5.4.3 Target of Known Depth
If there are no suitable hyperbolas visible in the data to perform the Hyperbola Matching described above,
it may be the situation that there is a target of known depth in the area being scanned. If this is the case,
use the bottom tip of the hyperbola matching triangle and move it until it lies on top of the GPR response to
the known target. Then, use the Vel+ and Vel- buttons to adjust the velocity value up or down until the
known target depth is correct. Once the depth is matched, the current velocity value is the one used for all
subsequent data acquisition.
Figure 5-11: If a target of known depth is visible in the GPR data image, it is possible to use this target to determine the velocity
of the material above the target. Ignoring the tails of the hyperbola superimposed on the data image (top left) and using the bottom
tip of the triangle, use the Left, Right, Up and Down buttons to move it until it lies on top of the GPR response to the known target
(top right). Then, use the Ve l+ and Vel- buttons to adjust the velocity value up or down until the known target depth listed on the
bottom of the screen is correct (bottom), in this case 0.6 m. Once the depth is matched, the current velocity value listed on the bot-
tom of the screen can be used for all subsequent data acquisition in the area, in this case 0.15 m/ns. This velocity can also be used
for an accurate depth axis when plotting the data to the screen or after it has been transferred to a PC.
If units are metres then depths will appear in metres and velocities in metres per nanosecond (m/ns). If
units are feet then depths will appear in feet and velocities in feet per nanosecond (ft/ns).