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Old 12-06-2019, 02:10 PM
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GPS help

I have a Magellan Explorer 100 I typically take with me when out riding or exploring. Last year I had to abandon my dual sport and I marked the spot with the GPS for the heck of it. Came home and showed the wife where it was stuck and the GPS coordinates were nothing close to what Google maps showed. Then I did the same on our house out of curousity. My GPS says one thing and google maps says something different. Not being very comprehensive on GPS Long/lat positioning, Im lost as to what is going on.
The first 2 digits of lat/long on my GPS, 34xxxxxx by 110xxxxx matches that of my house on google maps, but after the first 2 digits everything is different.
Now I suppose as of this afternoon I kinda answered my own question here, but im still curious as to the 2 different GPS coords. I just found, today, that if I google map my house, put the curser over their home and click it twice, it will bring up a set of coordinates in a box at the bottom. These I assumed were our homes gps coordinates. Now put the curser over those coordinates and they'll get highlighted. Click on them and now another set of coordinates shows that is actually what my GPS shows, but is different from the first set of coordinates that google maps showed? Hope that makes sense. Bottom line is, I wondered if my GPS is correct In the event I had to pinpoint a location. I kinda asked this to a group of people some time ago, and was told it depended on what format my GPS using for Longitude and Latitude. Isnt there only one form or true Long/Lat value?

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Old 12-07-2019, 02:44 PM   #2
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There are different formats within a given coordinate system. Are you sure that both of the coordinates you get from the GPS and google are using the same format? For instance, one being 34.xxxxxx and the other being 34 XX.xxxx. The space being the critical point here. That would imply integer Degrees and decimal Minutes as opposed to decimal Degrees.
The only other thing I can think of off-hand is that your Magellan could be set to NAD27 to match forest service topo maps where Google uses the WGS84 system.
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Old 12-07-2019, 03:34 PM   #3
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Differences or errors in lat/long numbers can be attributed to setting your GPS for the wrong Datum like described at https://en.wikipedia.org/wiki/Geodetic_datum. WGS84 is the most common Datum used in the US, you just have to make sure your Datum is the same as the one you're referencing otherwise you can get an apples to oranges difference. Set yours for WGS84 and you should be fine. Most GPS receivers come set for WGS84 but not all do.

Years ago I had a new GPS and I failed to set its Datum to match the one used to generate a lat/long I was trying to find. That caused me to drive around in the desert for an hour looking for the campsite that was actually a mile or so away.

Also, there are several lat/lon format used, which have nothing to do with the Datum. There are some differences in their accuracy potentials. Set your GPS to standardize on the format you're mostly seeing. Some GPS's can apparently figure it out for you depending on how it's keyed in but not all.

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Old 12-07-2019, 07:36 PM
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Here is an example of the two different values I get on google maps. The first comes up just entering my address, the second is my clicking on my address coordinates which brings up the other set of values and also what my hand held GPS shows. Perhaps you can or tell whats what right off the get go. Thank you guys!
34.329076, -110.115041
3419'44.7"N 11006'54.2"W
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Old 12-07-2019, 08:42 PM   #5
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Quote:
Originally Posted by 8thtimer View Post
Here is an example of the two different values I get on google maps. The first comes up just entering my address, the second is my clicking on my address coordinates which brings up the other set of values and also what my hand held GPS shows. Perhaps you can or tell whats what right off the get go. Thank you guys!
34.329076, -110.115041
3419'44.7"N 11006'54.2"W
Did you read the information immediately above your last post?
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Old 12-08-2019, 10:47 AM
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Hello Jerry,
I reading up on all of this this am. I was unaware of the different operating systems and that there are several variances. Being one who asks many questions, I have lots of reading to do to hope to understand things better. I can grasp an earth grid of long/lat points, but how would that work flying at 30K feet or in outer space? Looks like Im gonna have to find out.
Thank You!.
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Old 12-08-2019, 01:00 PM   #7
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Just figure out how to make sure your GPS is using WGS84 for its Datum setting. My Garmin GPS has multiple Datum selections to choose from in its setup section, the desired WGS84 is one of them.
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Old 12-16-2019, 06:21 PM   #8
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GPS is much better than LORAN was as long as you have your method of entry correct: https://www.wikihow.com/Write-Latitude-and-Longitude.

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