Measuring Position - Sensors & Software pulseEKKO Product Manual

11.2.2 Free Run
If the Trigger Method
followed:
a) Set the antennas at the correct separation and centred on the starting position for the
survey line.
b) Press the Start button on the DVL screen.
c) The system starts to beep, indicating a data trace is being collected. The antennas should
be kept in contact with the ground surface while the system is beeping.
d) When the beeping stops, one trace has been collected.
e) Move the antennas together along the survey line a distance equal to the Step Size
distance. If you are moving the system in a vehicle or boat, for example, make sure you
maintain the constant speed that was set.
5. Then back to c) to repeat the cycle.

11.3 Measuring Position

A critical part of GPR surveys is accurately locating subsurface objects. When an odometer is
used (as in the SmartCart, SmartTow or SmartChariot systems), this is easy as the GPR is
triggered via the odometer at regularly spaced intervals. However, when using a full bistatic
configuration, the user needs to manually trigger the system at periodic intervals. In most
cases, a measuring tape is used to control position. In this case, make sure it is NOT metal or
does NOT have a metal center. Some cloth tape measures do have metal centers. Odd effects
can appear in data when such measuring tapes are used.
When collecting a GPR line where the accuracy need only be accurate to the nearest metre, set
the step size equal to some fraction of your antenna spacing. On the rope used to hold the
antennas at a fixed spacing, mark the step size with tape or a zip tie. Each time the antennas
are moved mark the ground (take note of a mark or feature) where the next antenna placement
will be based on the mark on the string.
(6.2.3) is set to Free Run, the following data collection sequence is
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Surveying Techniques & Tips