Geoscience Reference
In-Depth Information
profile generated from data collected along a transect oriented perpendicular to the drain lines. The
reflection hyperbola apex coincides with the top of pipe position. A banded linear feature is the
drainage pipe response most commonly found on a GPR profile generated from data collected along
a transect oriented directly along trend over a buried drainage pipe (Figure 29.3b, Figure 29.3d,
Figure 29.4b and Figure 29.4e). The position of the top of the banded feature corresponds to the top
of the buried drain line.
Figure 29.5 displays 250 MHz antenna drainage pipe detection results for a test plot in northwest
Ohio and provides a good example of the drainage pipe response shown on GPR profiles generated
from measurements collected along transects that are not oriented 90° (perpendicular) or 0° (along
trend) to the drain line. Figure 29.5a is a west-to-east GPR profile, Figure 29.5b is a south-to-north
GPR profile, Figure 29.5c is a GPR time-slice amplitude map of the test plot, and Figure 29.5d
is an interpreted map of the drainage pipe pattern based on the time-slice amplitude map. The
Figure 29.5d interpreted map shows all the drain lines trending east-west except one that trends
southeast-northwest. The measurement transect for the south-to-north GPR profile (Figure 29.5b)
crosses the southeast-northwest drain line at an angle of 60°, and the measurement transect for
the west-to-east GPR profile (Figure 29.5a) crosses the southeast-northwest drain line at an angle
We st
East
South
North
-0.46
-0.46
0.00
0.00
0.46
0.46
0.88
0.88
1.33
1.33
1.75
1.75
0.0
4.0
11.6
Line Distance (m)
7.6
15.2
19.2
22.9
0.0
4.0
7.6
11.6
15.2
19.2
22.9
Line Distance (m)
(a)
(b)
22.9
22.9
19.2
19.2
30°
15.2
15.2
60°
11.6
11.6
7.6
7.6
4.0
4.0
N
N
0.0
0.0
22.9
0.0
4.0
7.6
11.6
Distance (m)
15.2
19.2
22.9
0.0
4.0
7.6
11.6
Distance (m)
15.2
19.2
(c)
(d)
fIGURe 29.5
Ground-penetrating radar (GPR) results from a test plot in northwest Ohio emphasizing
changes in the GPR drainage pipe response due to different orientations of the GPR measurement transect
relative to the drain line, (a) west to east GPR profile, (b) south to north GPR profile, (c) 25 to 40 ns GPR time-
slice amplitude map, and (d) interpreted map of drainage pipe pattern. (Dashed black lines represent drainage
pipes, and solid gray lines show the position of the GPR measurement transects of profiles a and b.)
