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I would like to puchase a GPS for my auto, will use for driving directions as well as Caching. Would like to find one that I can change the Map Datum from Longitude/Latitude to UTM Coordinates. I use an Etrex 20 hand held to do most caching, but want one I can dash mount to view while driving. Any suggestions? Thanks Glassman 501

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Have you looked at the Garmin Nuvi models?

There are many different models at different price ranges. Depends on what you want (features) and how much you want to spend. For the most part, you can load the Nuvi's with geocaches using POI Loader and GSAK.

 

There's also Tom Tom units - but I'm not familiar with them so I won't specify.

Edited by Lieblweb
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No, they can't do it. You can't easily see current coordinates either. As mentioned, I guess it would be useful knowing how specifically you plan on using this information. Although the OP only talks about position format, datum may also require changing depending on the reason for the information.

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I would like to puchase a GPS for my auto, will use for driving directions as well as Caching. Would like to find one that I can change the Map Datum from Longitude/Latitude to UTM Coordinates. I use an Etrex 20 hand held to do most caching, but want one I can dash mount to view while driving. Any suggestions? Thanks Glassman 501

Yes, the Garmin Montana will do all this. UTM posistion format, driving directions (you will want City Navigator or 24k Topo for your area & the powered auto mount for spoken directions). In auto profile and in the auto mount, it's like a nüvi, except you can also have BirdsEye images (etc) that a nüvi doesn't do. Great for caching.
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...datum may also require changing depending on the reason for the information.

 

Map Datum should never be changed unless you are using your GPS with a map that was created with a different Map Datum, or you are navigating to coordinates created with a different Map Datum.

 

The most commonly used (and considered the standard) map datum in use is WGS 84.

 

Unless you have specific information indicating your maps or coordinates were created with a different Map Datum, DO NOT adjust your GPSr away from WGS 84.

 

Doing so will only lead to much grief and anxiety.

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Not really. Only if you are manually entering coordinates or manually comparing coordinates. Then, obviously, the datum of the coordinates being entered must match the settings on the GPS. As long as you are electronically transferring the coordinates, you are safe.

 

The main reason for changing the datum on the unit is to match up coordinates with a map printed in that datum. This is very common as other than very new maps, they are printed in other datums.

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Not really. Only if you are manually entering coordinates or manually comparing coordinates. Then, obviously, the datum of the coordinates being entered must match the settings on the GPS.

 

Got that backwards.

 

The GPSr datum must match the datum the coordinates were created with.

 

As long as you are electronically transferring the coordinates, you are safe.

 

I don't think so.

 

When you transfer coordinates (i.e. waypoints) to your GPS, manually or 'electronically', the GPSr has no idea what map datum was in use when the coordinates were created, and certainly has no ability to magically convert them to whatever map datum you have your GPSr set to. If this were the case, you would not need an option to change the map datum on your GPSr.

 

The main reason for changing the datum on the unit is to match up coordinates with a map printed in that datum.

 

As stated, The GPSr datum must match the datum the coordinates were created with.

Edited by BMW JEDI
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When you transfer coordinates (i.e. waypoints) to your GPS, manually or 'electronically', the GPSr has no idea what map datum was in use when the coordinates were created, and certainly has no ability to magically convert them to whatever map datum you have your GPSr set to. If this were the case, you would not need an option to change the map datum on your GPSr.

Programs that you use to send coordinates convert to the coordinates required by the schema or the schema includes datum information. It is the same as with such things as time formatting. Unless you are using some homemade program or such, you would never have a problem.

 

For instance, the GPX schema mandates WGS84. You can have your GPS set to any datum. When you send the file to the GPS, it knows the coordinates are in WGS84 and shows them in the correct location. Display on the GPS will be in whatever datum it is set to. Try it yourself before you say I'm wrong... I've done this many times and I guarantee I'm correct.

Edited by Red90
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Programs that you use to send coordinates convert to the coordinates required by the schema or the schema includes datum information. It is the same as with such things as time formatting. Unless you are using some homemade program or such, you would never have a problem.

 

For instance, the GPX schema mandates WGS84. You can have your GPS set to any datum. When you send the file to the GPS, it knows the coordinates are in WGS84 and shows them in the correct location. Display on the GPS will be in whatever datum it is set to. Try it yourself before you say I'm wrong... I've done this many times and I guarantee I'm correct.

 

I just created and saved a 'Test' waypoint on my Garmin GPSr.

 

Opened the GPX file with a text editor and this is what I see:

 

<?xml version="1.0" encoding="UTF-8" standalone="no" ?><gpx xmlns="http://www.topografix.com/GPX/1/1"'>http://www.topografix.com/GPX/1/1" xmlns:gpxx="http://www.garmin.com/xmlschemas/GpxExtensions/v3"'>http://www.garmin.com/xmlschemas/GpxExtensions/v3" xmlns:wptx1="http://www.garmin.com/xmlschemas/WaypointExtension/v1"'>http://www.garmin.com/xmlschemas/WaypointExtension/v1" xmlns:gpxtpx="http://www.garmin.com/xmlschemas/TrackPointExtension/v1"'>http://www.garmin.com/xmlschemas/TrackPointExtension/v1" creator="Oregon 650" version="1.1" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.topografix.com/GPX/1/1 http://www.topografix.com/GPX/1/1/gpx.xsd http://www.garmin.com/xmlschemas/GpxExtensions/v3 http://www8.garmin.com/xmlschemas/GpxExtensionsv3.xsd http://www.garmin.com/xmlschemas/TrackStatsExtension/v1 http://www8.garmin.com/xmlschemas/TrackStatsExtension.xsd http://www.garmin.com/xmlschemas/WaypointExtension/v1 http://www8.garmin.com/xmlschemas/WaypointExtensionv1.xsd http://www.garmin.com/xmlschemas/TrackPointExtension/v1 http://www.garmin.com/xmlschemas/TrackPointExtensionv1.xsd"><metadata><link href="http://www.garmin.com"><text>Garmin International</text></link><time>2013-03-26T17:22:56Z</time></metadata><wpt lat="34.862194" lon="-111.761384"><time>2013-03-26T18:52:24Z</time><name>Test</name><sym>Final Location</sym></wpt></gpx>

 

What part of that file tells the GPSr what Map Datum to use? If the information is present, and GPS devices can read it and adjust properly on the fly, why do we need the option to change Map Datum in the GPS settings?

 

Thank you for your help!

Edited by BMW JEDI
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The GPX schema is always in WGS84. the GPS and every GPS program know that... Some schemas state the datum.

 

Try this.... Change to some other datum on the GPS. Make a waypoint manually and note down the numbers... Now connect to a computer, and look at the GPX file. You will find the coordinates in the file are in WGS84 datum, so the numbers will be different than what you manual entered.

 

You change datums on the GPS, to allow comparison against a printed map. This is a common thing here. You are out in the wilderness and carrying topographic maps. You want to pinpoint your location on the maps. The map is printed in NAD27Canada and the grid is UTM. You set your GPS to this and look at your location and can find it on the map very accurately. WGS84 can be 100s of meters off. When you change the datum, the waypoints are still all in the correct location. The GPS internally is always using the same datum. The datum change is just for the user interface.

Edited by Red90
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I would like to puchase a GPS for my auto, will use for driving directions as well as Caching. Would like to find one that I can change the Map Datum from Longitude/Latitude to UTM Coordinates. I use an Etrex 20 hand held to do most caching, but want one I can dash mount to view while driving. Any suggestions? Thanks Glassman 501

Yes, the Garmin Montana will do all this. UTM posistion format, driving directions (you will want City Navigator or 24k Topo for your area & the powered auto mount for spoken directions). In auto profile and in the auto mount, it's like a nüvi, except you can also have BirdsEye images (etc) that a nüvi doesn't do. Great for caching.

 

My Nuvi 500 also has the ability to use multiple different Coordinate systems, the list is several pages long even. It also has a Geocaching function, something that the newer Nuvi's don't have. It is however obsolete and so I wouldn't recommend even looking for a used one. While I've only had a Montana a couple of weeks, I can second the comment 'Great for caching'.

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