
12
Correct Stake Orientation
When placing stakes, correct orientation is important.
For checking purposes, the orientation of the pin relative to the locator is shown in Figure 16.
Check the pin with one orientation. Then rotate
the pin 180°. The orientation that gives the largest
reading is the one that should be used. This
reading should be positive in the Northern
Hemisphere and negative in the Southern
Hemisphere.
An iron pin has two types of magnetization. One
is the magnetization induced by the Earth's
magnetic field. The induced magnetization is
always downward in the Northern Magnetic
Hemisphere and produces a positive output no
matter which end of the stake is driven into the
ground. The other type of field is the permanent
magnetization that is fixed to the pin. For
maximum detection, the stake should be driven
into the ground such that the permanent
magnetization is in the same direction as the
induced magnetization.
Locating Manholes, Septic Tanks and Well Casings
The magnetic field is strongest at the edge of a shallow manhole
cover. You can easily trace the edges of covers near the
surface. Locating depths for manhole covers range up to 9 feet.
Figure 17: Locating Manhole Covers
The great length of a well casing provides a strong field at the
surface that makes it easy to locate casings buried up to 16 feet
deep.
Figure 18: Locating Water Well Casings
Figure 16: Checking a Stake’s
Orientation