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25 lines
1.4 KiB
HTML
25 lines
1.4 KiB
HTML
<html>
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<head>
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<title>GPS Datum Example</title>
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</head>
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<body>
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<h1>GPS Datum Example</h1>
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<p>The following example of GPS datum differences was kindly provided by Randy Steele of Apollo, Pennsylvania (URL: <<a href="http://www.nb.net/~resteele/">http://www.nb.net/~resteele/</a>>) and is archived here so that a permanent link is available from <a href="http://www.xmpp.org/extensions/sep-0080.html">XEP-0080: User Geolocation</a>.</p>
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<p>BEGIN EXAMPLE</p>
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<hr />
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<p>This is an example of the differences in the datums you can use with a GPS.
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Below is a site I was checking out. I marked it on my GPS in the field. When I got back
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home to find it on the topo map, I noticed something was not right. Using
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the UTM coordinates from the GPS, I located the site on the topo map. But
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the map site and the site I checked in the field did not match. The terrain
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was different, the site I actually checked was near the road (the top red
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circle). I then remembered about map datums. The topo map was made to NAD27, while
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my GPS was set to WGS84. After changing the GPS to the NAD27 datum, all was fine.
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So the moral of this story is: MAKE SURE THE GPS DATUM AND THE MAP DATUM MATCH!!!
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Note the difference in the circle locations. I also changed my GPS datum to NAD27.</p>
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<p><img src='gps_datum.gif' alt='GPS Datum Example' longdesc='An example of different GPS readings when using a datum of NAD27 vs. WGS84, provided by Randy Steele'/>
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<hr />
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<p>END EXAMPLE</p>
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</body>
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</html>
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