Mounted search and rescue

[Una Smith <una.smith@att.net>]

As a child I spent a lot of time in corn fields, playing hide&seek
and looking for animals.  I don't recall corn being much worse than
the tall grass hay I also played in, that gave nasty cuts.  Someone
with dementia, who liked playing in the corn as a child, might be
expected to go into the corn.

Irv wrote:
>The first rule of any incident is never assume.

That's right.  The probability of the subject being in a given area
(POA) does not change once an area has been searched.  Searching
changes the probability of detecting the subject (POD) from 0 to
some value approaching 1.  Probability of success (POS) = POA x POD.
So it is a mistake to hasty search an area and declare it "clear",
ie that POA = 0.

In this case, let's say the global prior probability of the subject
being in a corn field is X.  But there 1000 corn fields in the
vicinity of his town.  Let's say they are all equal area, and 
equally accessible.  He can be in only one of them, so POA for each
is X/1000.  If X is 10%, then POA is 0.1/1000 = 0.0001.  Not likely.
Now consider POD.  POD is a function of search effort.  POD per
groundpounder day spent in a corn field is very low, because the
corn is dense and tall.  Searchers might need to walk every row
or at least every other row.  A quarter mile is 1320 feet.  If the
corn rows are planted 2 feet on center then there are 1320/2=660 
rows and the distance to be walked between them is 660 rows / 4
rows per mile = 165 miles.  To walk a single average corn field
that is 1/4 mile square would take somewhere on the order of 20
groundpounder days.  That is assuming a person could walk 8 miles
in a corn field in one day, probably a very optimistic assumption.

How much searcher effort would you put into searching a corn field
with such a low POA?  Not much, especially when you know the field
will be harvested soon, and harvesting will yield a very high POD
for essentially 0 searcher effort.

To search low POA, high effort fields, I would want to use air
scenting animals, dogs or horses.

        Una Smith
        New Mexico