There seems to be a gradual increase in the use of metal
detectors to assist in relocating trig blocks. Perhaps we
could share information. To start with an obvious question
- how useful are they?
The OS sometimes made a block easier to find either by
covering it with a piece of scrap metal or by using an
'emplacement ring' containing phosphor-bronze (known to
trig baggers as a concrete ring). Issues affecting the
detection would include depth (surface block - typically
a few inches; buried block - a couple of feet); also the
amount of vegetation cover and perhaps also moisture
content of the ground.
The OS would have had better access to details about the
siting of a trig block; for example, a sketch with
measurements to nearby points of reference; maybe
undocumented information and perhaps also temporary markers.
I don't know how much detector technology has changed in
the 50+ years since the blocks were originally placed.
Probably lighter, cheaper and with more sophisticated displays.
But is the detection fundamentally better?
From a trig baggers point of view, the bulk and weight of
carrying a detector to a remote spot could be an issue.
Its use could also provoke a response from others,
especially when visiting land where permitted access could
not be assumed.
Are modern detectors prone to false-positives; i.e. signalling
a find when theres nothing there? I'd guess that, in a typical
trig location, the chance of finding a spurious metallic object
is relatively low, especially if the search zone is initially
reduced with a GPS device.
Any do's, don'ts, makes/models recommended or best avoided?
How about metal-detector phone apps?
Opinions gratefully received, even if you think that detectors
are a waste of time!