Appendix C: Calculating Gps Latency - SPX SPIDAR NIC-500s Operation Manual

Appendix C: Calculating GPS Latency

Appendix C: Calculating GPS Latency
This section explains how to calculate the GPS latency. Remember this only applies when
collecting data on a fast-moving platform.
1. Choose a large outdoor area with a clear view of the sky, like a parking lot.
2. In the center of the area, place a metallic disk, roughly 1 ft in diameter. You can use a foil
covered piece of cardboard. It is advised that the disk be taped down so that it does not move.
3. Set up your GPR to collect GPS data as well. Make sure that the GPS is centered directly
over top of the GPR unit (as shown below).
4. Set GPR recording Depth to 0.50m (10.1ns) so that data can be collected quickly without
skipping traces.
5. Start a new line and collect data running over the disk in a flower pattern (see figure below).
Try to run over the disk in as many different directions and as many different speeds as you
can. The faster the data are collected over the plate, the more accurate the latency value will
be. ** Make sure no traces are skipped. **
6. Export the GPZ data from the flash memory card and open it in the EKKO_Project software.
MapView should display your GPS path like this:
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