Geophysical Survey Systems, Inc.
SIR® 4000
Manual
MN72-433 Rev F
97
4
GSSI recommends sampling at 512 or 1024 samples/scan for most applications. More samples will be
required for deep geologic or polar ice thickness applications.
5
Scans/Unit
•
Scans/Unit allows you to adjust the number of scans per unit of horizontal distance when you are
collecting with a survey wheel. A unit of measure will appear based on the Units selected from
the Introduction Screen and the Horizontal Units selected from the Output Menu.
•
Smaller scan spacing produces higher resolution data, larger file sizes, and may require slower
data collection. For example, if you see a 12 here and the system is set to English feet, rather than
Metric units, you will collect 12 scans per foot, or 1 per inch.
•
Scan spacing will vary based on application. For example, 5-10 scans/inch (60-120 scans/foot) is
the optimal range for shallow structural features in concrete, but with lower frequency antennas a
coarser scan density of 12-24 scans/foot is typical.
6
Scans/Mark:
Set how many units (i.e., feet or meters) will be collected between system marks.
These marks will appear at the top of the data display along the horizontal scale.
7
Dielectric/Soil Type:
Choose a Dielectric Constant or Soil Type that best represents the area you are
surveying (See Appendix D: Dielectric Values for Common Materials). Modifying the Dielectric will
automatically adjust the Time Range, and vice versa.
8
Depth/Time Range:
There are two options for setting the depth or time range.
Depth Range:
The vertical scale displayed in whichever units are selected under the Output ->
Vertical Units menu.
•
Depth Range can be set from 1cm to 10000cm (0.4-3900 in).
Time Range:
The vertical scale in nanoseconds (ns) within which the SIR 4000 will record
reflections. It is proportional to depth viewed because a higher Time Range will allow the energy to
penetrate deeper and return deeper reflections.
o
Time Range can be set from 1-20000 ns.
o
It is important to remember that the Time Range is two-way travel time, so that a range of 50
ns means that the deepest possible reflector is at 25 ns.
o
A very long range may require a greater number of samples to create enough data dots for the
scan curve. Refer to the section above to determine the appropriate number of samples/scan.
o
Please see Appendix D for a list of common ranges for individual antennas.
o
Modifying Depth Range will automatically update the Time Range. Modifying Dielectric will
also update the Time Range.
9
LineTrac
:
Set LineTrac On or Off. There are two settings that can be adjusted when LineTrac is
turned On: Power Mode and Frequency Mode. When Power Mode is turned On a blue line will
appear at the base of the LineScan. When Frequency Mode is On a yellow line will appear. If both
Modes are turned on, a blue and a yellow line will appear.
Note:
When adjusting time/depth range in Digital 2D mode with the 350HS antenna, the
following procedure is recommended. Before changing the time range, press the red Stop
button to suspend communications with the antenna. Next, change time or depth range. Finally,
exit the Radar menu, and then press the Init button.
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