GPR4 Concrete Scanner – User Manual
D-000002-000021
Earth Science Systems, LLC
February 29, 2019
Copyright © 2019 ESS, LLC. All rights reserved.
Page 16 of 28
6. The
GPR4 Record
tab has standard A-scan and B-scan plots that are customary for
most GPR systems. The plot parameters can be changed by pressing the
Plot
parameters
button
(see Figure 5). For most users, the default settings will be
sufficient. For those interested, the dialog functions are described below.
a.
Use automatic range gain
When this is selected the program automatically
increases gain with increasing range to compensate for signal attenuation with
range. The gain profile is automatically readjusted at the start of each line.
b.
Automatic zero time
Use this setting to move the first arrival to the beginning of
the plot.
c.
Antenna combination
For the Pavement Scanner, this should always be set to
TxA RxA
.
d.
Depth/Time units
Select the units for the vertical scale on the B-scan. The most
basic units are sample number (
Samples
). Sample number multiplied by the
digitizer sample period gives sample time (
Nanoseconds
). Sample time
multiplied by the medium velocity gives distance (
Centimeters
,
Inches
,
Meters
,
Feet
).
e.
Depth/Time range
Users can opt to display the full range, half range, quarter
range, or eighth range. Users may wish to display only a shallow portion of the
usable range when interested in the more shallow portions of the surveyed range
(depth).
f.
Velocity of medium
The velocity of EM waves is dependent on the material type.
In order to properly convert from time of flight to depth, the velocity of the
medium must selected (see
Depth/Time units
above). Select the medium type
and the corresponding dielectric constant. The EM velocity is
ε
ν
/
c
=
where
v
is the EM wave velocity,
c
is the speed of light in a vacuum, and
ε
is the dielectric
constant of the medium.
Air
ε
= 1
Dry concrete/indoor/mature - Dry soil
ε
= 4
Damp concrete/outdoor - Damp soil
ε
= 6.5
Moist concrete/outdoor/young - Moist soil
ε
= 9
Wet concrete/outdoor/young - Wet soil
ε
= 16
Saturated concrete/outdoor - Saturated soil
ε
= 25
g.
Distance units
Select the units for the horizontal scale on the B-scan
(
Centimeters
,
Inches
,
Meters
,
Feet
,
Seconds
).
h.
Distance range
Select the horizontal range of the B-scan in distance units (
10
,
20
,
50
,
100
,
200
).
The
GPR4 Record
tab also has buttons for saving the B-scan image
and generating
a short report
. The image can be saved as a PNG, BMP, or JPG file. The report will
be saved as a PDF file, and will contain the survey metadata and the B-scan image.
7. The
Survey Grid
tab shows how the linear traverses making up the survey will be
arranged. This step can be skipped when only conducting a single scan line. These
traverses are planned using the
button and the dialog shown in Figure 5. To type
