[DS2] Question About Spotting Mine Fields

I'm working on a scenario for DS which involves one
side making a penetration attack through a mine field
to take a crossing point on a river.  The mine field
is represented by a 3:1 mix of mine and dummy
counters.  According to the rules pre-laid mine
counters should be placed face down and only turned
over once an element comes within the 2 inches of the
counter.

So the question is, should a unit be able to discover
if the counter is a dummy marker (or not) without
running through the minefield?

How does it work in the Real World?  Is it possible
for a non-specialist unit to discover a mine field
before they start hitting mines?  Or is it possible
for a VTOL to spot a minefield?

--
J.Friant

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