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GPS Location transformation to other coordinate systems

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07-21-2010 08:27 AM
AndrewEgleton
New Contributor III
Hi

I may have missed something in the documentation, but is there a way to tranform the GPS location into other grid systems on the fly?

Our services are all using British National Grid and the GPS location is consistantly ~150m NW of where we are actually standing, which is what I'd expect to see when using a non-transformed location.
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5 Replies
PaulJereb
New Contributor
Hi Andrew,

I was looking for an answer to the same question, did you find out how to transform the coordinates?

BR, Paul
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DannyHatcher
Esri Contributor
Andrew,

The only good way to do it that I've found is to use an AGSGeometryServiceTask and call the projectGeometries:toSpatialReference: function.  It requires a call to the server each time you wish to do a conversion but the geometry service is normally fairly quick and you can send them in as batches if you wish.  If you are just displaying GPS you could just make the call each time you receive a new GPS coordinate and then display your own graphic.
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PaulJereb
New Contributor
Could you post an example of how to do that?

Paul
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AndrewEgleton
New Contributor III
Thanks, I will look into it. I suspect that it may result in too many calls to the server, especially when lots of people are using it at the same time.
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DiveshGoyal
Esri Regular Contributor
Andrew,

The map already projects the coordinates returned by the device (always WGS84) into the spatial reference of the map (in your case, British Grid). Are you saying that results are inaccurate (~150m) and that a different/custom datum transformation would yield better results?

Would it be possible for you to share the map you're using so that we can run a few tests?

Thanks.
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