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Author Topic: GPS data does not match tile set  (Read 4222 times)

gumnut

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GPS data does not match tile set
« on: April 28, 2005, 10:19:49 PM »
I am just trialing this program and have downloaded my GPS trail data from an older style Garmin. Unfortunately, my trail appears about 3km NNE of where I would expect to be on the tile set. I am working from Melbourne Australia.

Is there some way to adjust my trail so that it appears in the correct location?
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jmstacey

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GPS data does not match tile set
« Reply #1 on: April 28, 2005, 11:16:09 PM »
Do you have the same datum set in TopoFusion as on your unit?

Quote
Is there some way to adjust my trail so that it appears in the correct location?

Not that I know of, however I didn't write TopoFusion...
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gumnut

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GPS data does not match tile set
« Reply #2 on: April 28, 2005, 11:46:37 PM »
How can I find out if my GPS dataset and topfusion dataset is different or the same?
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Alan

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GPS data does not match tile set
« Reply #3 on: April 29, 2005, 12:53:39 AM »
The garmin protocol specifies the transfer datum (WGS84 I believe) and we believe that we handle it correctly.  Unfortunatley, we've notices that some sets of tiles are offset on TerraServer.  A good example is near Tucson where TopoFusion first starts up.  As you keep moving east you can actually see where the break is.

We've considered adding some sort of "local adjustment" to bump the tiles (or tracks) by a certain number of meters, but haven't done so, nor figured out how to provide an interface for it.
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