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#46098 - 08/06/05 08:41 AM Terraserver vs. GPS
camerono Offline
Member

Registered: 02/19/05
Posts: 146
I am really confused. Does anyone have any idea why.. On Terraserver my home coordinates are Latitude 41.96272 Longitude -87.66402

However on my GPS they are Latitude 41.57762 Longitude -87.39803

I know for a fact that my Garmin GPS is in sync because I go geocaching all of the time. But Terraserver gives me a precise satellite photo of my home.

Any idea why the difference and couldn't this conflict be a little dangerous. The difference is about 75 miles give or take.

If you know why this is happening please let me know or help me figure it out.

Thanks

Cameron
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#46099 - 08/06/05 02:57 PM Re: Terraserver vs. GPS
garrett Offline
Enthusiast

Registered: 03/07/03
Posts: 249
Loc: North Carolina
Have you checked the datum on your GPS versus terra server? I don't use Terra Server all tht often, so I don't know what datum they use, but most of the time, when you have an issue with different coords, it is usually the map datum.

The other option is that they are incorrect.

Good luck,

Garrett
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On occasion of every accident that befalls you, remember to turn to yourself and inquire what power you have for turning it to use. - Epictetus

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#46100 - 08/06/05 06:32 PM Re: Terraserver vs. GPS
GoatRider Offline
Old Hand

Registered: 08/28/04
Posts: 835
Loc: Maple Grove, MN
I'll bet you've got your GPS set to a different format of lat-long. Terraserver, and most internet mapping programs, are DD.ddddd, but I'll bet you've got your's set to DD-mm.mmmm' or even DD-mm'ss.ss"
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- Benton

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#46101 - 08/06/05 06:38 PM Re: Terraserver vs. GPS
groo Offline
Old Hand

Registered: 11/02/03
Posts: 740
Loc: Florida
Good catch.

41.57762 -> 41 deg, 57.762 minutes , 57.762 / 60 = 0.9627, so it's 41.9627 decimal degrees.


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#46102 - 08/09/05 01:13 AM Re: Terraserver vs. GPS
MartinFocazio Offline

Pooh-Bah

Registered: 01/21/03
Posts: 2203
Loc: Bucks County PA
One of two things is going on.
Your GPS is, in all probability, using the WGS-84 Dataum, while the vast majority of topo maps use NAD-27. There can be pretty major differences in position data.

the other issue might be the format of your lat/long display.

40.56734 degrees is not the same is 40 56.734 which is 40 degress 56.734 minutes.

But you should really be learning and using UTM anyway, even for Geocaching. It's a better, faster and easier system to use and it's well supported by Geocache. These problems don't exist in UTM at all, and for geocaching UTM just plain kicks butt.

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