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8. Positioning
It is better to choose the positioning before data acquiring to correctly determine
the location and/or geometric dimensions (traveled distance) of the acquiring GPR profile,
because it will help while data processing and interpreting. The profile's traveled distance
(its length) is used to locate targets relative to its starting point. There are many positioning
methods, the main ones implemented in the Prism2 software and consisting of:
Manual
– manual way of positioning. User has to measure the traveled distance by
some measuring device (tape measure, odometer, laser meter, etc.) for the manual
method and then enter measured value manually while acquired data saving to the
hard drive, or to the Output parameters menu item. parameters) (see below in
section 11. Working with sounding data files on page 50).
Wheel
– survey wheel method of positioning. It is possible to use different types of
measuring wheels (for example, our current measuring wheel has a diameter of 200
mm, a shock-proof cart wheel has the diameter of 250 mm, but a built-in 1500 MHz
antenna wheel has the diameter of 80 mm). The wheel positioning can be selected
in the main menu (see Fig. 8.1) or in the GPR Setup (take a look on Section 9. GPR
tuning at the page 34). The GPR has a wheel interface and counts pulses got from
the wheel encoder. Software has to know the wheel parameters to recalculate it to
the traveled distance. A difference of a few mm in diameter can lead to meter errors
while measuring the traveled distance. There are two possibilities to describe the
wheel:
o
Parametric
- the software allows adding (fig. 8.2), editing (fig. 8.3) or selecting
previously added wheel. The main parameters of the wheel are diameter (in mm)
and number of pulses per revolution, which you will find on the wheel.
Fig.8.1. Survey wheel settings
