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# Using lat-lon coordinates from map to gps

Posted on 2009-04-09
261 Views
Hi,
I have an old sea map (1967) which is using lat-lon coordinates.
What I need to do be able to read and type the coordinates I see on
the map to my gps and find that place. The problem is that I 1.
dont know how to read the map correctly 2. don^t know what grid system the map is using
....3. so I can use which?? system on my gps settings.
Pls help I have been reading articles in the inet about earth lat-lon and still can^t do it.
I can scan and send you the map if needed
0
Question by:gsazeides

LVL 38

Expert Comment

ID: 24107587
gsazeides,

Check the edges of the map. That should have the information you need, in what's called the "legend". If you can, post what what you can that might be useful, or scan the legend (not the whole map itself), and post that.

Cheers,
LHerrou
0

Author Comment

ID: 24114003
Ignore the red line and 2 dots on the map. Lets say that I want the coordinates for my eTrex Hc Carmin
for the end of the land between latitude 3825-3826 and longtitude 503-504. My gps Position format is set to hddd mm.mmm´ and the map datum to WGS 84.

The position for that point given by the gps is
N   34 34,274`
E 033 01,824´
I don^t understand why is like that. Should^t it be sthg different?
Picture.jpg
0

LVL 4

Accepted Solution

docbert earned 125 total points
ID: 24624671
The grid system it's using is called "Universal Transverse Mercator", or UTM.  UTM is based on the "Mercator projection", which maps the world into a cylinder, and is normally used for nautical charts as it allows for the representation of straight lines as straight lines, which is not possible with many other mapping projections due to the fact you're trying to map a round earth onto a flat piece of paper!

The UTM coordinates for the point you're referring to are made up of the numbers on the sides of the map, along with 3 additional digits for the location within the cell. So your "land between latitude 3825-3826" becomes a "Northing" of "3825250" whilst the "longtitude 503-504" becomes an "Easting" of "503400".

You will also need to know the "Zone number", which will be printed on the map.  In this case the zone number will be "36S"

There are many websites which will covert between UTM and DMS (Degrees Minutes Seconds). One of the better ones is http://pages.globetrotter.net/roule/utmgoogle.htm which will not only allow you to convert between the two, but will display the resulting location on Google Maps for you.
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