topic Re: WebMercator and NAD27 - WGS-84 issue in ArcGIS API for Silverlight Questions

WebMercator and NAD27 - WGS-84 issue

LuisGarcia2 — Thu, 11 Oct 2012 17:55:08 GMT

I have several graphics that I add on a Graphic Layer. This is how I add them to the layer:

WebMercator wm = new WebMercator();          ESRI.ArcGIS.Client.Graphic g =  new  ESRI.ArcGIS.Client.Graphic(); MapPoint p = new MapPoint(myLongitud, myLatitude, null);  SimpleMarkerSymbol mark = new SimpleMarkerSymbol(); mark.Color = myColor;   g.Geometry = WM.FromGeographic(p); g.Symbol = mark; g.SetZIndex(0);  GraphicsLayer.Add(g);

Now, all the data we have in our database that is fill in with those two variables in the MapPoint object (myLongitud and myLatitude) is in NAD27. We are displaying in that same Silverlight control map some services that are in WGS-84 and we notice there is a little difference in the position of the graphics with respect to the objects shown from the service. Do I need to make a conversion to project my graphics? How do I do that?
Thanks!

Re: WebMercator and NAD27 - WGS-84 issue

JenniferNery — Thu, 11 Oct 2012 18:24:03 GMT

You can set GraphicsLayer.ProjectionService as seen in this SDK sample (see XAML-code): Auto-Project. WebMercator can only be used for converting geometries between Bing Maps WebMercator projection (SRID=3857) and WGS84 Geographic coordinate system (SRID=4326).

Re: WebMercator and NAD27 - WGS-84 issue

LuisGarcia2 — Thu, 11 Oct 2012 20:14:15 GMT

Thanks for your response. I see several spatial references HERE and in the example I see they use 4326. So, for my my spatial ference what should I use?

MapPoint p = new MapPoint(myLongitude, myLatitude, new SpatialReference(4326));

Or should I use the Spatial reference in which they are? NAD27? In which case I guess I would have to find it in that list?

thanks again and excuse my ignorance on this, it is pretty new to me.

Re: WebMercator and NAD27 - WGS-84 issue

JenniferNery — Thu, 11 Oct 2012 22:06:42 GMT

According to this: Geographic Coordinate Systems listing , it is WKID=4267

Re: WebMercator and NAD27 - WGS-84 issue

LuisGarcia2 — Fri, 12 Oct 2012 12:39:57 GMT

Jennifer,
Thanks! That was it!.

Re: WebMercator and NAD27 - WGS-84 issue

LuisGarcia2 — Fri, 12 Oct 2012 13:07:35 GMT

One more question on this, now regarding the service itself. We need to transform a large number of geographic locations at a time. I may need to do 600 or so, sometimes more at a time. Is there a way to send a batch to the service? If not, we were using an Object WebMercator as explained before. This was faster compared to using Geometry Server, is there something similar to WebMercator for the projections I need to make?
Thanks!

Re: WebMercator and NAD27 - WGS-84 issue

DominiqueBroux — Fri, 12 Oct 2012 15:52:08 GMT

The ProjectAsync method accepts a list of graphics as input argument and project all the graphics in one request to the server.
Is it what you are looking for?