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I've noticed when I change my map datum on my GPS/Fish finder my coordinates change when in a still position. This tells me if I don't have it to the right setting, I would be looking in the wrong places if following a set of coordinates. There are about a dozen settings. Is there a place in the Destin area I can pull my boat up to with a KNOWN gps reference point and check it?

This out of my Humminbird 997CI manual:

Map Datum allows you to change the map coordinate system used by the 900 series to match those of a paper map.
Map Datum setting. (Default = WGS 84)

See you on the water in July.
 

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wgs 84 should be the correct setting, that's what I've always used. any others settings,I've had problems finding spots
 

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from the wonderful world of wiki.........

WGS 84 is the World Geodetic System of 1984. It is the reference frame used by the U.S. Department of Defense (DoD) and is defined by the National Geospatial-Intelligence Agency (NGA) (formerly the National Imagery and Mapping Agency) (formerly the Defense Mapping Agency). WGS 84 is used by DoD for all its mapping, charting, surveying, and navigation needs, including its GPS "broadcast" and "precise" orbits. WGS 84 was defined in January 1987 using Doppler satellite surveying techniques. It was used as the reference frame for broadcast GPS Ephemerides (orbits) beginning January 23, 1987. At 0000 GMT January 2, 1994, WGS 84 was upgraded in accuracy using GPS measurements. The formal name then became WGS 84 (G730), since the upgrade date coincided with the start of GPS Week 730. It became the reference frame for broadcast orbits on June 28, 1994. At 0000 GMT September 30, 1996 (the start of GPS Week 873), WGS 84 was redefined again and was more closely aligned with International Earth Rotation Service (IERS) Terrestrial Reference Frame (ITRF) 94. It is now formally called WGS 84 (G873). WGS 84 (G873) was adopted as the reference frame for broadcast orbits on January 29, 1997<SUP class=reference id=cite_ref-0>[1]</SUP>.

The WGS84 datum, which is almost identical to the NAD83 datum used in North America, is the only world referencing system in place today. WGS84 is the default standard datum for coordinates stored in recreational and commercial GPS units.

Users of GPS are cautioned that they must always check the datum of the maps they are using. To correctly enter, display, and to store map related map coordinates, the datum of the map must be entered into the GPS map datum field.

DATUM is any surface with which the elevations are referred. The MEAN SEA LEVEL affords a convenient DATUM
 

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Howdy,

Correct - WGS 1984 or NAD 83 are interchangeable and the current datum to set your GPS.

For some strange reason, our federal government till uses NAD 27 datum when providing coordinates for oil platforms, etc. You can be over 100' feet off if trying to find a NAD 27 point when your unit is set for NAD 83.

If you get a coordinate in NAD 27, you can convert it to NAD 83 by going to; <a href="http://www.ngs.noaa.gov/cgi-bin/nadcon.prl">http://www.ngs.noaa.gov/cgi-bin/nadcon.prl</a>

You can convert single coordinates by inputting the lat/long coordinates into the windows very easily, or if you have multiple points, you can provide a file but this takes a little more expertise.

Have a GREAT Memorial Day weekend, and remember the reason - Thank our troops.

Tom Hilton
 
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