NaviTrack® II
signal. (See Figure 27 below). The signal should peak over the line and drop off on either side. The Signal Angle indicator will be near zero when the NaviTrack II is directly above the line.
Trace
Line (Solid)
Distortion
Line (Dashed)
Figure 27 – High Probability Locate
3.When tracing, the direction the pipe or cable is run- ning will be shown on the screen with 2 lines, one solid and one dashed. The solid line (the Tracing line) is the signal as seen by the lower antenna node and the dashed line (the Distortion Line) is the signal as seen by the upper one. (See Figure 27.)
4.The Tracing line has three important functions. It represents the location, and the direction, of the sig- nal being traced. It reflects changes in direction of the target utility — when the utility makes a turn, for ex- ample. And it helps recognize signal distortion, when compared to the dashed line — if something is inter- fering with the signal and distorting its shape, the dashed line could be significantly offset or skewed.
5.Use the Proximity Number, Signal Strength, and Tracing and Distortion lines to guide the line trace. These three pieces of information are generated from discrete signal characteristics to help the oper- ator discern the quality of the locate. An undistorted signal emitted from a line is strongest directly over that line. By maximizing the Proximity Signal, and cen- tering the Tracing and Distortion lines on the screen the confidence in a “good” locate is high. Confirm a lo- cate by testing whether the Measured Depth reading is stable and reasonable.
Testing for the consistency of the Measured Depth read- ing can be done by raising the NaviTrack II a known dis- tance (say, 12" exactly) and observing whether the Measured Depth indicator increases by the same amount. Small variation is acceptable, but if the Measured Depth does not change, or changes drastically, it is an indication of a “distorted” field, or a very low level signal on the line. As always, the only way to be completely certain of the location of a utility is through visual inspection by ex- posing the utility.
NOTE! The accuracy of position and Measured Depth measurements improves as the NaviTrack’s low- er antenna node is placed closer and closer to the target utility. Rechecking the Measured Depth and position periodically during the excavation process can help avoid damage to a target utility and may identify additional utility signals that were not noticed prior to excavation.
WARNING
Care should be taken to watch for signal interfer- ence that may give inaccurate readings. The Tracing line is only representative of the position of the buried utility if the field is UNDISTORTED. Do NOT base your locate solely on the Tracing Line.
Always cross check your locate by ensuring that:
•The Tracing Line and the Distortion Line are substantially aligned.
•The Proximity Signal and the Signal Strength maximize when the Tracing Line crosses the map center.
•The Measured Depth increases appropriately as you raise the unit vertically and the Tracing Line and the Distortion Line remain aligned.
Measured Depth readings should be taken as esti- mates and actual depths should be independently verified by potholing or other means prior to digging.
Note on 93 kHz Frequency Use
NOTE! European versions of the NaviTrack II offer an additional 93 kHz frequency for Line Tracing.
The default 93 kHz frequency has an actual cycle count of 93,696 cycles per second.
Some older transmitters use a different value for the nominal 93 kHz frequency, 93,622.9 cycles per sec- ond.
If you find that your transmitter signal at 93 kHz cannot be detected by the NaviTrack II, set the locator’s fre- quency to
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