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7.5
Pinpointing
In order to save time in the recovery of an object and to reduce the size of
the hole required to extract it from the ground, it is necessary to pinpoint
the exact location of the object. The technique described here will be
particularly useful with the Double ‘D’ coil, but will also work with a Monoloop
coil.
When a likely object is detected, sweep the general area with the coil,
taking note of where the strongest signal is received. Raise and lower the
coil to one side of the target to make sure you are still ground balanced. If
necessary balance the detector again, then recheck the signal. If the ground
balance is accurate you may begin the pinpointing procedure. Decrease
the length of the sweep and it should be possible to draw an imaginary line
in the ground where the strongest signal is located (see figure 9). Now,
move around the target and sweep the coil at 90 degrees to the initial
direction. Repeat the process of drawing an imaginary line. Where the two
imaginary lines cross is where the object is located.
Figure 9 - Pinpointing Procedure
If using a Monoloop coil, small shallow
nuggets will give a signal near the rim
of the coil. An alternative pinpointing
technique for Monoloop coils is to turn
the detector coil on its side and move
the coil while it is vertical across where
you suspect the target to be. This may
assist in pinpointing as shown in figure
10.
The Minelab SD2200v2
Figure 10 - Alternative Pinpointing
Instruction Manual
7.6
Digging the Target
Once you have established the location of the target it is necessary to dig
a small hole to recover it. In order to preserve the environment, it is essential
to make the hole as small as possible and always replace any soil and
grass that you have removed. Carry at least one of the following digging
tools with you when searching. The best tools are:
·
a small, strong, digging spade
·
a pick
·
a shovel
·
a crowbar (for very deep objects in hard ground).
Before digging, clear the area of loose surface material and check that the
sound is still there. If it is not, the target must be among the surface material.
If the signal is still there, dig down 50mm to 100mm. If the target is not
visible, sweep over the hole. If the signal has gone then it must be in the
pile just dug. Make sure that there are no objects buried in the soil.
Take care when you dig because damaging a nugget can reduce its value.
Minelab suggests you start digging about 100mm in front of the target to
reduce the chance of damage. Pile the diggings carefully as it might be
necessary to search them systematically later. They must also be replaced,
just as they were dug, once your search ends.
If it becomes evident that the target is in the removed soil pile, sweep the
coil over the pile and pinpoint where it lies. Progressively halve the pile
containing the target. If the target is still difficult to find, lay the detector
down with the coil flat on the ground. Take a handful of the diggings and
pass them over the coil. If there is no signal, place the handful carefully
away from the pile and repeat with another handful. Of course, your hands
and wrists must be free of any metallic jewellery and watches. Once the
object has been recovered it is a good idea to sweep the hole again to
ensure that there are no other targets to be detected.
When you have found an object in a particular hole, search the surrounding
area very carefully as it is very likely that there are more objects nearby. If
you hear a target, keep searching until you find it. It is there and it might be
valuable.
Note: Refill the hole you have dug, and leave the area as you found it.
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