User Manual

2150GR Ground Penetrating Radar
054-139 - Rev. 1
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o For equal propagation speed, depth and type of target, the hyperbola will be wider
for geometrically larger targets (for examples for wider diameter pipes).
When interpreting the maps, it is a good idea to remember that the width of a hyperbola does
not just depend on the geometrical size and shape of the target.
Fig. 7-2 shows two maps featuring echoes of an irregular interface between two layers with
different dielectric properties (asphalt) and six pipes situated perpendicularly to the direction
of investigation.
Fig. 7-2 – Maps showing traces of an interface and
pipes perpendicular to the direction of investigation
As can be seen in Fig. 7-2, the echo of a target doesn’t simply consist of a single dark band,
it consists of alternate dark and light bands. These derive from the signal minimums and
maximums reflected back from the target (in fact, the black and white bands represented in
the figure correspond to maximum and minimum signal amplitude respectively).
A hyperbolic echo can be used to convert the ordinate of the map from time (nanoseconds =
ns) to depth (meters= m). To do this, the hyperbola traced in ns ordinates is compared with a
family of hyperbolas traced with ordinates in meters, obtained from that in ns ordinates with
various values of v
m
. The best v
m
approximation to the real value is that with the most
similar aperture to that of the one traced in time ordinate. Once v
m
has been identified, the
depth of the target corresponding to the hyperbolic section can be found.
interfaces
: Top
surface of
the pipes