
Determining Target Depth by Triangulation
The receiver can be used for the traditional triangulation method to determine the approximate depth of a target as illus-
trated in Figure 5-10. However, when using this method it is necessary to take into account the fact that the center of
the cable-sensor is located 11 inches up the receiver tube from the black tip. When the position of the target has been
determined by the null, mark the spot (#1) on the ground. Hold the receiver tip on the ground at this spot, slant the
instrument at a 45° angle and slowly move directly back, to one side, from the target until a second null is obtained.
Now mark a spot (#2) on the ground that is directly below a point 11 inches up the receiver tube from the black tip.
Measure the distance between spot #1 and spot #2. This measurement indicates the approximate depth of the target.
Figure 5-10. Determining Approximate Depth of Target
Schonstedt Instrument Company
5-7
MARK SPOT 2
MARK SPOT 1
TARGET
DISTANCE
EQUALS
DEPTH OF
TARGET
NOTE
You should always take a depth reading on both sides of the line. If the
measured distances between spots #1 and #2 on both sides of the line are
not the same, there is a good chance that a nearby line is causing the two
measurements to be different. Move further along the line and repeat the
depth reading procedure until the measurements are the same on both
sides of the line. Once two very similar measurements are obtained, the
calculated depth of the cable will always be within 4 to 6 inches of its actual
depth. “Simple geometry calculations never give an incorrect indication of
depth.” Push-Button depth indications provided by some products are
affected by soil composition, salinity, and moisture content and have been
reported to be off by up to 2-1/2 feet.
45 Degrees