topic Re: Proj.NET and 102100 Projection in ArcGIS API for Silverlight Questions

Proj.NET and 102100 Projection

DanielWalton — Tue, 15 Jun 2010 13:42:24 GMT

I am using the ProjNET library to do reprojection in the client for popular coordinate systems. When I try to specify 102100 as a destination coordinate system (using several variant WKT's), the points always have a y-error of about 20km (in SoCal). Is there anyone out there who has successfully modified this library (I'm guessing with a shift grid) to support 102100 as a destination? I really would like to be able to drop the ESRI.ArcGIS.Client.Bing.dll from my project references!

Thanks,
Dan

Re: Proj.NET and 102100 Projection

dotMorten_esri — Tue, 15 Jun 2010 15:01:13 GMT

What is the from coordinate system?
On a side note, webmercator projection will be in the core API at the next release, so you won't need Bing by then (it will also support reprojecting entire geometries and not just points)

Re: Proj.NET and 102100 Projection

DanielWalton — Tue, 15 Jun 2010 15:03:18 GMT

What is the from coordinate system?
On a side note, webmercator projection will be in the core API at the next release, so you won't need Bing by then (it will also support reprojecting entire geometries and not just points)

Source projections are lat/long (KML) and various Albers projections (shapefiles). They all seem to have the same y-error and all show up fine in 4326.

-Dan

Re: Proj.NET and 102100 Projection

dotMorten_esri — Tue, 15 Jun 2010 15:39:45 GMT

Are they all using the WGS84 datum? If not, I don't think you will have much luck with anything but the projection service.

Re: Proj.NET and 102100 Projection

DanielWalton — Tue, 15 Jun 2010 15:42:37 GMT

Are they all using the WGS84 datum? If not, I don't think you will have much luck with anything but the projection service.

Why not? Obviously the ESRI.ArcGIS.Client.Bing library is able to do this in the client. Is it proprietary ?

Thanks,
Dan

Re: Proj.NET and 102100 Projection

dotMorten_esri — Tue, 15 Jun 2010 15:45:47 GMT

No it's not able to do a datum transform. The input MUST be EPSG:4326, or it will throw an exception.
http://help.arcgis.com/en/webapi/silverlight/apiref/topic2392.html

Re: Proj.NET and 102100 Projection

DanielWalton — Tue, 15 Jun 2010 16:03:20 GMT

Yes, all my test cases use the WGS84 datum. Using the Bing assembly they all visualize correctly over a 102100 map service, and with ProjNet they all show up 20km south.

Thanks,
Dan