10
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 15.
Check the pin with one orientation. Then
rotate the pin 180°. The orientation which
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.
Figure 15: Checking a Stake’s Orientation
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 which 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 depth ranges up to 12 feet.
Figure 16: Locating Manhole Covers
