Question for GPS users

[gyork]

How do you have your units for Lat and Long set on your GPS? Many guides list degrees/minutes/seconds (e.g 43^o 41'12.0'). When free-scrolling on MITA on-line Master chart, units are listed in the lower right corner as degrees/degree/100,000 which I find not a little cumbersome. I prefer degrees/minutes/[minute/1000] (e.g. 43^o 41.200 or 43.41.200) which geocachers list/use. I find this designation easier to use when calculating waypoints on the fly.

gary

[Dan Foster]

I've never seen a nautical chart that didn't have grid lines labeled in degrees and minutes of latitude and longitude. On the water, I'd stick with that format instead of decimal degrees or deg min sec.

Another popular option is UTM coordinates, since the UTM grid is rectangular, not curved like lat/lon, and the grid spacing is one kilometer. If you are going to be determining coordinates by looking at features on the map, UTM is much easier to use, since it's base10.

You should also be aware of the horizontal datum. Almost everything is WGS84 these days, unless you are using an old USGS topo map in NAD27 datum.

[JohnHuth]

Gary -

I'm not a GPS user, but I do celestial navigation with a sextant and watch. All of us who do that use degrees, then minutes and decimal minutes...

So… 41 deg 14.5 min is my typical format. Note that the best one can do with a sextant is 1/10th of an arc-minute, so I don't go beyond one decimal.

Can't help you with GPS, however. I could never get the hang of UTM either.

Best,

John

[lhunt]

Seems like you should be set up with whatever the Coast Guard would expect. These guys seem to agree on "Degrees, Minutes, Decimal Minutes, as in DD MM.mm". I didn't find an official site, but I didn't look all that hard :-)

Then if you have to make that call we never want to have to make, at least you have the correct format for the data.

Lisa

[leong]

Seems like you should be set up with whatever the Coast Guard would expect. These guys seem to agree on "Degrees, Minutes, Decimal Minutes, as in DD MM.mm". I didn't find an official site, but I didn't look all that hard :-)

Then if you have to make that call we never want to have to make, at least you have the correct format for the data.

Lisa

That’s right, Lisa.

The following are additional details from here:

Aeronautical/Maritime SAR Responders – (USAF/USCG) - Aeronautical SAR responders use latitude and longitude for SAR response. The standard Latitude/Longitude format is Degrees, Decimal Minutes (DD° MM.mm’). Latitude is always read and written first noting “North” since the U.S. is North of the Equator. Longitude is always read and written last noting “West” since the U.S. is west of the Prime Meridian. When speaking or reporting Latitude and Longitude use the following: For example, 39° 36.06’N by 76° 51.42’W, should be stated as per the following: “Three nine degrees, three six decimal zero six minutes North by seven six degrees, five one decimal four two minutes West.” The words, “degrees,” “minutes,” and “decimal” must to be spoken.

-Leon