Sensors & Software Conquest Series, Manual

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Conquest 5-Line Scans and Grid Scans
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One of the first things to note is the resolution of Conquest. Features will show up with a
minimum size of about 30 mm (1.5 inches). This is a fundamental limit of the transducer
response characteristics. You should not interpret a Conquest feature to be fully representative of
the dimension in the Depth Slice image. The object may be 1 inch in diameter or 1/8 of an inch in
diameter but it still will result in a 1.5 inch wide event on the depth slice image. You must be
careful about assigning size to features.
Step down through the depth slices and look for patterns. Normally regular patterns of rebar will
appear at different depths. Sometimes when a bar or conduit has a dip or a tilt, it will show up
partially at one depth and then show up at another depth more clearly as the bar or conduit cuts
down through the selected depth range.
The display allows you to view any pair of cross section images on the sides of the 3D view. This
is very instructive because you can see both the lateral position and the depth as you learn how
to use the three views.
Hyperbolic (inverted “V”) responses from crossing rebar perpendicularly are enhanced by turning
the Filter ON. The filter removes flat-lying reflectors in the cross section images. If your target is
flat-lying, like the bottom of concrete, make sure that the Filter is OFF.
The PCD image can also be displayed in the Slice View menu. The menu makes it easy to
toggle between the GPR Depth Slice images and the PCD image. Unlike depth slice images, the
PCD image is a single image that is NOT associated with a specific depth range.
Notice that, similar to GPR responses from rebar and other objects described above, the PCD
response are broad compared to the actual size of the cable so the width of the PCD response
has no relation on the size of the cable.
Details on displaying Depth Slice images are described in Help > Slice View .
5.9 Step 9: Interpretation of Results
You interpret the Conquest map results by looking for the dark areas on a light background or
light features on a dark background depending on the colour table. These areas indicate the
presence of an object in the subsurface at a particular depth.
In general, you will find that bars, pipes and conduits make straight lines across the depth slice
whereas layers and horizons such as the bottom of concrete show up as uniform coloring which
is somewhat marbled across the area.
Experience is required in understanding the images that you obtain. It is fairly straightforward to
get a first order sense of a site by stepping Up and Down through the depth slices to understand
the observations. You can see what depth you are at by looking at the slider bars on the side of
the vertical cross sections. By looking at the cross sections you can get a sense of what features
are occurring at different depths whereas the depth slice gives you the spatial location of these
features.
See Section 7: P33 for some examples and interpretation.