GE XL VU Operating Manual page 108

Measurement
Depth
The perpendicular distance between a surface and a point above or
below it.
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Place first three cursors on an even surface to define a reference plane.
Place the fourth cursor at the point of uncertain depth.
Note: Negative measurements indicate the point is below the plane.
Positive measurements indicate the point is above the plane.
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108 XL Vu™ VideoProbe