User's Manual

DIGITAL CONTROL INCORPORATED
DigiTrak Falcon
™
F5

Operator’s Manual 77
Appendix C: Projected Depth Versus Actual
Depth and the Fore/Aft Offset
What Happens When the Transmitter Is Steep and Deep
The signal field emitted by the transmitter consists of a set of elliptical signals, or “flux lines”.
The flux lines indicate the position of the transmitter. When the transmitter is level with
respect to the ground, the locate line (LL) is directly over the transmitter, the depth displayed
on the receiver is the actual depth, and the locate points (FLP and RLP) are at equal
distances from the transmitter. The location of the LL is found at the intersection of the
ground and the horizontal component of the flux field; the FLP and RLP are found where the
vertical components of the flux field intersect with the ground. Some of the horizontal and
vertical components are identified below by short yellow lines.
Side View of Flux Field and Geometry of FLP, RLP, and LL
Due to the shape of the transmitter’s signal field, when it is at a pitch greater than ±10%
(±5.7°) and/or a depth of 15 ft. or more, the position of the locate line will be some distance
ahead of or behind the transmitter’s actual position. In this case, the depth displayed on the
receiver becomes what is called the projected depth. The transmitter’s distance ahead of or
behind the locate line is called the fore/aft offset.
The projected depth and fore/aft offset must be accounted for when the transmitter is steep
and/or deep. See Table C1 and Table C2 to determine the actual depth and fore/aft offset
when you know the displayed (projected) depth and pitch of the transmitter.
FLP
LL
RLP