GSSI PaveScan RDM 2.0, Руководство пользователя

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Geophysical Survey Systems, Inc. PaveScan® RDM 2.0
Manual
MN36-716 Rev A 8
The GPS Settings screen is shown below. The current GPS status is indicated on
the top right. NMEA GGA sentences are updated at the GPS update rate when the
GPS is properly connected.
GPS Settings Screen
Baud Rate:
The Baud Rate of the GPS. The Baud Rate of the Garmin GPS that comes with the RDM
system is 9600.
Inline Offset (ft):
The inline offset of the GPS relative to the center sensor. If the GPS is in front of the
center when looking in the direction of travel, the value is positive. If the GPS is in back of the sensor
(e.g. between the sensor and the Toughpad) the value is negative.
Crossline Offset (ft):
The crossline offset of the GPS relative to the center of the cart. Typically, this
will be 0.0, but if the GPS is to the left of the center sensor looking in the direction of travel, the value is
positive. Correspondingly, if the GPS is to the right of the center sensor facing the direction of travel, the
value is negative.
GPS Time Lag (seconds):
For high-accuracy GPS systems, the lag, or time difference between the
arrival of the PaveScan dielectric measurement and the GPS position information can be calculated and
entered here. This value is then used to correct the time synchronization between the two measurements.
Typically, to calculate the GPS time lag, a number of measurements are made traversing over a location
where the dielectric contrasts with the surrounding asphalt (which can be achieved by placing a metal
strip on the asphalt). The GPS coordinates at this dielectric contrast are also known. Then, the data are
exported to Google Earth using different GPS Time Lags and the lag used that most closely corrects the
GPS locations of the exported data is subsequently used as the entry for this field. The accuracy of the
Garmin GPS that comes with the PaveScan RDM isn’t high enough to warrant using the GPS Time Lag
correction. By default, this value is 0.0.