UTM in search & rescue

On my scanner I've been monitoring the search for the missing hunter
in the mountains north of Los Angeles. He disappeared a week ago. Most
of the time the search teams are reporting their positions to the
command post in UTM. For example, "0436629 by 3796711". Usually they
omit the zone (11).

I'm puzzled by the leading zero on easting. Isn't the largest possible
easting less than 1000 km? If that's true, then the leading zero is a
do-nothing digit. It will never be anything but zero. Yet, on radio I
almost always hear UTM given that way.

Just now I tried out a couple of my GPS receivers. Neither one
displays a leading zero on easting. These are both Magellans, and not
recent models. Is it now the modern fashion to show easting and
northing with an equal number of digits?

Apparently there have been datum problems on this search and rescue
project. I overheard someone say that the coordinates have to be UTM
in NAD27 -- "that was our problem yesterday".

The search is suspended for the night, but I think it will resume
tomorrow. If you're in Los Angeles County and have a scanner, listen
to CTAC 2 (sheriff's countywide tactical channel #2) on 482.8375 MHz.
That's audible all over the county and beyond on the repeater system.
If that channel is needed for something else, they may switch the
operation to CTAC 1 (482.8125) or ATAC 1 (483.0875). I've heard all
those channels used for SAR. The ATAC channels have less coverage("A"
meaning "area", as opposed to countywide), so if they're on ATAC 1 you
may not hear anything if you're near that area.

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I said:

Correction -- it sounds like they're terminating the search because
the hunter was found deceased.

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Can't argue with that reasoning. As an old friend of mine would often
remark in jest, why do you always find things in the last place you look?

Keith

| On my scanner I've been monitoring the search for the missing hunter
| in the mountains north of Los Angeles. He disappeared a week ago. Most
| of the time the search teams are reporting their positions to the
| command post in UTM. For example, "0436629 by 3796711". Usually they
| omit the zone (11).

I'm surprised they don't use MGRS. "36629 by 96711" is easier to say,
and besides with MGRS there is a well defined way to chop off trailing
digits if you don't need all that precision - as in "3662 by 9671" or
even "366 by 967" if 100 meter accuracy is sufficient. (Actually, I
guess you're not even supposed to bother with the word "by" in the
middle, and say "366967"?)

As far as I understand, this is precisely why MGRS was invented: A
concise way to give a position within a limited area. You need to
bother with those pesky letters only if the area of operation is about
100 km wide or more, which is not likely in the typical SAR situation.

IIRC, MGRS was even renamed USNG and supposed to become the canonical
grid for civilian use in the US a few years ago. There were certainly
some lively discussions about it in this group at the time.

--
- It is undesirable to believe a proposition
when there is no ground whatsoever for supposing it is true.
-- Bertrand Russell

Harald Hanche-Olsen wrote:

While USNG is similar to MGRS they are not the same. For example USNG is
not defined outside the US and its territories. Datums are also defined
differently in the two systems.

Dale

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