User's Manual

Locating
44 DigiTrak
®
SE™ Operator’s Manual
Locate Points (FLP & RLP) and Locate Line (LL)
The SE receiver locates the transmitter by detecting three specific places in the transmitter’s magnetic
field: the locate points and the locate line. The locate points are indistinguishable from one another by the
receiver. They represent similar points in the transmitter’s field in front of and behind the transmitter. The
front locate point (FLP) is ahead of the transmitter, and the rear locate point (RLP) is behind the
transmitter. (See Appendix B for more information about the transmitter’s magnetic field.)
The locate line (LL) extends 90° to the left and right of the transmitter and represents the location of the
transmitter between the FLP and RLP.
The most accurate tracking requires the use of all three locations to determine the position, heading, and
depth of the transmitter. Aligning the FLP and RLP reveals the heading and left/right position of the
transmitter. The LL determines the central position and depth of the transmitter when the receiver is
properly aligned between the FLP and RLP. The full procedure for tracking is given later in this section
under “Standard Method for Locating the Transmitter.”
LL
Transmitter
FLP
RLP
Axis Line
Drill
Surface of
Ground
Drill
LL
Transmitter
FLP
RLP
Bird’s-Eye View
(Looking Down)
Side View
Geometry of FLP, RLP, and LL from Top (Bird’s-Eye) and Side Views
Note how the RLP and FLP are equal distances from the LL when the transmitter is level.
NOTE: If the transmitter pitch exceeds ±30% (or ±17°) and/or the transmitter depth exceeds 15 ft
(4.6 m), the position of the locate line will be somewhat ahead of or behind the transmitter’s
actual position. In these cases, the depth displayed on the receiver is referred to as the
projected depth (see Appendix B for more information regarding this situation).