San Jose Navigation GPS Mobile Locator GM-158-USB Instrukcja Użytkownika Pobierz pdf (Strona 31)

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8 Data examples and Interpretation

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Utilities are identified, as upside down “u” shaped objects know as

signatures or so called hyperbolas. An example of this is seen in Fig. 5.1

below. Note the direction of the GPR survey, marked with an arrow. The

direction is relatively perpendicular to the long axis of the utilities. A

signature does not form if a scan direction is parallel to the utility but rather

a linear feature is displayed.

Fig. 5.1. A radargram /cross section revealing a horizontal/parallel profile of

a water main. Note the arrow showing the direction of the survey.

Figure 5.2 shows a comparison between the “Shallow” and “Medium”

antennas. The radargrams are showing the same groups of utilities. Notice

the difference in resolution around the electrical conduits. Another

difference in the antennas can be seen by comparing the sharpness of the

force main in Figure 4.5 compared to that detected with the shallow

antenna.

Perpendicular

Storm Drain

Water Main parallel

to the scan

Lateral

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San Jose Navigation GPS Mobile Locator GM-158-USB Instrukcja Użytkownika Strona 31