User's Manual

DIGITAL CONTROL INCORPORATED

68 DigiTrak Falcon



Operator’s Manual

Side View of Actual Depth due to Fore/Aft Offset When Steep and Deep

The above figure shows a transmitter positioned in a drill string that is drilling at either a

positive or a negative pitch—the pitch is positive if you are drilling left to right, negative if you

are drilling right to left. The transmitter’s signal field is also pitched at the same angle as the

transmitter. The locate line (LL), which is where the depth measurement is taken, is the

horizontal component of the transmitter’s signal field flux lines. That is, the LL is found where

the flux lines are horizontal, illustrated by short horizontal yellow lines above.

The locate points (FLP and RLP) are also shown above. These points are located at the

vertical components of the signal field illustrated by short vertical yellow lines above. Note

how the locate points are not the same distance from the LL when the transmitter is pitched.

Again, this situation requires compensation for the projected depth and the fore/aft offset.

Using the following tables to find:

 actual depth based on the receiver’s depth reading (projected depth) and the transmitter

pitch – Table C1

 fore/aft offset based on the receiver’s depth reading (projected depth) and the

transmitter pitch – Table C2

 projected depth that you will see on the receiver during drilling if you know the required

depth (actual depth) of your installation – Table C3

 conversion factors for determining the projected depth from the actual depth, or the

actual depth from the projected depth at various transmitter pitches – Table C4

These "steep and deep" calculations for projected depth are important when using a bore

plan that has specified target depths on steeper and deeper bores.

Projected depth

Actual depth

30% (17°)

pitch

Fore/aft offset