GPS Location transformation to other coordinate systems

[AndrewEgleton]

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.

[PaulJereb]

Hi Andrew,

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

BR, Paul

[DannyHatcher]

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.

[PaulJereb]

Could you post an example of how to do that?

Paul

[AndrewEgleton]

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.

[DiveshGoyal]

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.