25
Fig. 4.2
. Example of measurement swaths and mapped objects in the surrounding for reference.
So called Tie-in points are used if the Total Station position needs to be moved. More can be read in
the operation manual for MIRASoft.
To control the actual data acquisition, an odometer (encoder) wheel is used to achieve a precise trace
interval (point distance). The encoder is mounted on the carrying vehicle and directly connected to
standard antenna box and the ProEx control unit. The wheel controls the data acquisition along the
survey line while the positioning system logs the position at predefined times/events. When selecting
the point distance, one should use a distance no longer than the channel spacing within the array. To
get good data for the radar and the positioning a suitable speed for a survey is roughly 20 km/hour.
Note!
The encoder on the carrier wheel should be placed in line with the Total Station Prism or the
GPR rover antenna to ensure a good quality length measurement.
As previously shown, a spray can, attached to the antenna array box, is advisable to use to mark the
edge of the swath measured, and by that see where the next swath should be measured to get
sufficient. Minor, uncovered, areas do not result in significantly deteriorated data, though. See an
example in Figure 4.3.
Fig. 4.3
. Example of radar data were the radar swaths are not completely overlapped, leaving
unmeasured white spots in the data.
