Geophysical Survey Systems, Inc.
SIR® 4000
Manual
MN72-433 Rev F
151
Appendix F: Basic LineTrac Setup and
Interpreting Field Data
GSSI’s LineTrac is an optional accessory for digital GPR
antennas. LineTrac is a sensitive and versatile locating device
that measures the AC current of powered utilities and induced
frequencies in non-powered utilities. Two modes are
available: Power Mode, a passive detection mode that tracks
AC current in energized lines; and Frequency Mode, where
the device tracks a specific frequency that has been user-
induced into a utility line.
The LineTrac is installed on a digital antenna via four screws
near the front of the antenna. The device is then plugged
directly into the digital antenna via the integrated accessory
port. When the SIR 4000 is powered on, you will see a Green
Indicator Light on the top of the LineTrac. To begin using the
LineTrac you must configure settings in the Collect/Setup
screen. Select the Radar Menu, and scroll to the bottom using
the Control Knob. Turn LineTrac On.
Next, select either Power Mode, Frequency Mode, or both, and
choose the appropriate settings for your survey.
•
Power Mode can be set to 0, 50 or 60.
•
Power Mode is a passive detection method that can
locate the AC current of energized cables that are
under load. These frequencies are typically 50Hz or
60Hz.
•
Frequency Mode can be set to 1, 8, 16, or 33 KHz.
•
Frequency Mode is an active detection method used in
combination with a user-supplied signal application
device. Set the value of Frequency Mode to match the
frequency of the applied signal.
Once the LineTrac settings are configured, enter the Collection
Screen by pressing the Green Start Button on the SIR 4000. As
you move the antenna, LineTrac data will scroll across the
screen with the GPR data. Power Mode data will appear as a
blue line and Frequency Mode data will be yellow. You will
notice many small data peaks in the absence of a large Power
or Frequency target. When you approach a real target the small
spikes will be minimized and a large Power or Frequency
spike will appear. As you pass over the energized target the
spike will build to a peak (Power Mode) or two peaks with a
trough between them (Frequency Mode). As you move beyond
the target the LineTrac readings will decrease. You can then
pull the antenna backwards and center the Backup Cursor on
the target based on the GPR data, Power Mode peak, or the
Accessory
Port
Attachment
Screws
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