SubSurface Instruments AML Operator's Manual page 14

- Depth Estimate via Triangulation – True of any locator using this method -
Ground Level
NOT Drawn to Scale!
The triangle on the right, if drawn to scale,
would have vertical and horizontal sides
"equal" -- The depth equals the distance
between the two "marked spots", as long
as the "laser pointer line" is at a 45
degree angle... depending on the
diameter of the target.
*unless the target is not of a small diameter. See the bottom of the corner of the triangle
above as it (hidden) meets at the center of the target... so it will be "shallower" then the
distance between the "spots", or about ½ the diameter of the target.
"AML" held Vertical
Pinpoint position
Laser
Pointer
Line
Distance between "spots" is the depth*
Marked Laser Spot
(We're picking the center
detectable "edge" of the
target for this example –
not the outside edges.)
Buried
Target
Pipe
At 45 degree angle
Laser
Pointer
Line
Marked Laser Spot
Now, notice the triangle at the left does not
completely reach to a "point" at the bottom,
the two sides do not "join" at the bottom.
The vertical side comes off the closest
point: the top of the pipe. The 45 degree
angle comes off the closest point of the
angle in that direction, so the sides do not
meet.
So. If the target were a "wire", the distance
would be extremely accurate. If the target is
a 48" diameter pipe, the measurement
would be off 2 feet... The top of the pipe
would be 2' higher than the measured
distance, because the sides of the triangle
come to a point in the center of the pipe.
So: KNOW YOUR TARGET!
"AML" held
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