SPX SPIDAR NIC-500s, Operation Manual, Page: 44 / 119

SPIDAR Software
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The table below lists some default time windows and their associated depth of penetration,
assuming a velocity of 0.1 m/ns (or 0.328 ft/ns).
Frequency (MHz) Time Window (ns) Approx. Depth (m) Approx. Depth (ft)
12.5 1600 80 260
25 800 40 130
50 400 20 65
100 200 10 33
200 100 5 16
500 50 2.5 8
1000 25 1.25 4
Changing the time window will correspondingly change the points per trace (described below).
Points per trace
A trace is collected each time the GPR pulses and records new data at a specified location.
The trace contains all the data (as data points) from the top of the scan to the bottom of the time
window.
The points per trace is related to the Time Sampling Interval as per the equation below:
Points per trace = Time Window / Time Sampling Interval
Changing the points per trace will make a corresponding change in the time sampling interval,
such that the value for time window is maintained.
The value for points per trace must be between 70 and 30,000.
It is more common for the user to change the time sampling interval (below) than it is to change
the points per trace. Changing the sampling interval will automatically adjust the points per
trace.
Note : Points per trace must be set the same for the GPRs on a single NIC-500. Points per
trace can be different between NIC-500s on a daisy chained system.