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AVTM651070 Rev B Nov 2006
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Offset Magnetic Field Identification
When adjacent cables or pipes are present in the right of way, they will
sometimes create locating errors. Some of the transmitted signal is picked up by
nearby conductors or pipes and reradiated so that it adds to or subtracts from the
original signal. The result is an offset magnetic field that can cause path locating
errors.
You can verify the presence of this problem by using triangulation to measure
depth, as described in the preceding section on Depth Measurement 45° Angle
Method. If the right side and the left side depth readings agree to within about 5
in. (12.7 cm), your path locate is fairly accurate. If the two depth readings do not
agree, your path locate is not accurate. You can decrease the error by marking the
path as being about halfway between the two outside depth locate marks. This
important strategy can be used to obtain the most dependable path location
possible. See Figure 15.
Summary of Contents for L1070
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