Questions on Lat/Long

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I have a couple of questions on reading lat/long from different sources. A map I'm looking at reads -93.25108 45.04682 for a point. I know that this is N 45 and W 93. Is it 25 min and 4 min? If so then the seconds would be 108 and 682. How does that convert or does it convert to 60 seconds.

Next question. How do you know what datum is used on different maps? Maybe it's listed on quad maps and I've never noticed it.

Thanks a bunch. Glad to be getting started in this hobby.

This comes up a lot when you first use a GPS. The long/lat comes in 3 different formats. What you are looking at is D.DDDD (degree and fractions of degree). Geocaching uses D M.MMMMM (degree/minutes and fractions of minutes) and what you are used to looking at would be d m s (degree/minutes/seconds). Your GPS should be able to change the format under one of it's settings. If you want to convert it manually here is a site that will help you change it.

http://neilm.com/whitejeep/convert.mv

No, the coordinates are degree.decimal. Basically, degrees and base 10 fractions of a degree. Degree, minute.decimal is usually shown with a space or a line:

34 10.335

34-10.335

Same with Degree, minute, second.decimal:

34 10 20.1

34-10-20.1

Datum is usually printed on the legends of maps. You can also get a list of all current USGS quads, publication date, and datum on the USGS website.

-jjf

You're right, I just couldn't think of the proper phrasing. Thanks.

Multiply the decimal portion by 60

.04682 x 60 = 2.8092 = 45°2.8092'

.25108 x 60 = 15.0648 = 93°15.0648

.8092 x 60 = 48.552 = 45°2'48.552"

.0648 x 60 = 3.888 = 93°15'3.888"

To go from seconds back to minutes back to degrees, then divide by 60 instead of multiply

Thanks a ton folks. I think I have it mostly figured out now. Makes much more sense.

Look in the lower-left of USGS maps for the datum.

Old ones will probably be NAD27.

DustyJacket

...If life was fair, a banana split would cure cancer.

Without making assumptions one really wouldn't have a clue what the format "really" is.

One might/could assume (and that's not real clever at times) that it is decimal degrees but after seeing the many different variations with written formats that really one is only guessing.

There should be absolute NO reason to guess a position format, none what so ever.

http://www.cqnet.com.au/~user/aitken/gps/format.htm

Cheers, Kerry.

I never get lost everybody keeps telling me where to go

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