[aprssig] APRS LAT/LONG standards

Curt, WE7U archer at eskimo.com
Fri May 27 12:00:51 EDT 2005

On Thu, 26 May 2005, Robert Bruninga wrote:

> >>> steve at dimse.com 5/26/2005 4:19:39 PM >>>
> >Curt has already pointed out aircraft use decimal
> >degrees.
> But he is wrong.  Every pilot and Naval Avaiator
> here in the Aerospace Departement and every
> naval officer fully qualified in Navigation says so.

I just spoke to one of our Helo crew for SAR.  He's not one of our
pilots but he's proficient with compass and GPS, does some of our
training on such matters, and he's been on the Helo crew for a few

He says that they _don't_ use DD.DDDDD format in the helo.  They
prefer UTM in most cases, which is of course what the
ground-pounders are using in our county as well.  If they need to go
to Lat/Long format in the Helo it sounds like they use DD MM.MMM
format just as Bob says.

They have a couple of GPS's in there and can switch to other
coordinate systems when necessary, but they always seem to be busy
keeping the darned thing in the air so they don't play with the GPS
unless they have to.  It stays in UTM nearly all the time.

Sorry to cause a bit of confusion on this thread.  They say memory
is the 2nd thing to go.  I can't remember what the first is!

Seriously, I do remember having to convert to/from decimal degrees
at base before, having to do with helicopter operations.  It may
have been just another one of those cases where we didn't and
couldn't get the GPS format info at the time.  Sometimes things get
real busy when they're doing helo stuff and we must maintain radio
silence unless we're directly associated with the helo operation
under progress.  It's a safety thing.  In that case we would have
been trying all formats in order to cover all our bases, plotting
objects on the map to see which ones were outside our search area,
and asking questions about GPS format later after the critical helo
operations were concluded.

I also asked about the military choppers, but he couldn't remember
what their capabilities were with respect to GPS formats.  We've
been assisted in the past by blackhawks and chinooks from Fort
Lewis, and by some other type of heavy-lifting chopper from Whidbey
Island Naval Air Station.  I remember they were capable of something
other than MGRS in all or nearly all of those cases, probably
lat/long DD MM.MMM format again.  I don't think we were using UTM
with any of them.

Thanks for persisting on this issue Bob.  It made me ask more

Curt, WE7U.   APRS Client Comparisons: http://www.eskimo.com/~archer
"Lotto:    A tax on people who are bad at math." -- unknown
"Windows:  Microsoft's tax on computer illiterates." -- WE7U
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