NaviTrack® II
When line tracing, it is important to remember that Tees, curves, other conductors in the vicinity, and nearby masses of metal can add distortion to the field requiring closer scrutiny of the data to determine the path of the target. These distortions are likely to be worse when trac- ing passively.
For best accuracy, use directly connected Active Line Tracing whenever possible.
WARNING
In Passive Line tracing, or when signals are ex- tremely weak, the Measured Depth will generally read too DEEP and the actual buried depth may be MUCH shallower.
Operating Tips for Active Line and Passive Line Tracing
•The NaviTrack II quickly identifies distorted fields. If the lines are not centered on the map, when the Proximity Signal or Signal Strength is maximized, distortion is creating a complex
1.Try changing the frequency used to a lower one.
2.Move the ground stake position away from the line being traced.
3.Make sure that the line is not commonly bonded to another utility. Undo common bonds only if safe to do so.
4.Move the transmitter to a different point on the line, if possible.
•If the tracing lines will not center or if they move across the screen erratically, then the NaviTrack II may not be receiving a clear signal. The Measured Depth and the Proximity Signal may also be unstable under these circumstances.
1.Check the transmitter to be sure that it is operating and well grounded.
2.Test the circuit by pointing the lower antenna at ei- ther transmitter lead.
3.Check that the NaviTrack II and transmitter are op- erating on the same frequency.
4.Try different frequencies, starting with the lowest, until the line can be picked up dependably.
5.
•Using the Signal Angle Indicator is another way to check for distorted signals. Move the NaviTrack II perpendicularly to both sides of the traced line until the Signal Angle Indicator reads 45 degrees. Be sure to keep the lower Omnidirectional antenna node at the same height and the locator level. If there is little or no distortion the traced line should be in the middle and the distance to each 45 degree point should be ap- proximately the same on either side.
Another variation of this technique is to move the same distance to the right and left of the traced line, say 24 inches (60 cm) and check that the Signal Strength read- ings are similar.
Same Distance
45° Point | 45° Point |
Energized Pipe
Figure 30 – Checking for Distortion
•While tracing, the Proximity Signal and Signal Strength should maximize, and the Measured Depth should minimize at the same place where the lines center on the display. If this is not the case, the utility may be changing direction or other coupled signals may be pre- sent.
•Higher frequencies bleed over to adjacent utilities more readily, but may be needed to jump breaks in tracer wires or go over insulating couplers. If the line is un- grounded at the far end, higher frequencies may be the only means to make the line visible (See on page 28).
•When using the transmitter inductively, be sure to begin the locate about 30 feet (10m) away to avoid “di- rect coupling”, also known as air coupling. This occurs when the NaviTrack II picks up the signal from the
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