Latitude and Longtitude

[StanleyHo]

Hi,

I need to draw polygons on the map but the polygon  coordinates is based on latitude and longitude.

How do I convert latitude and longitude from map X and Y coordinate?
How do I do the reverse?

[DavidMartin]

You can use the GeometryService to project between different coordinate systems. The Project tool will also take a datum transformation if needed. See http://resources.arcgis.com/en/help/runtime-wpf/apiref/index.html?ESRI.ArcGIS.Client~ESRI.ArcGIS.Cli...

[StanleyHo]

Thanks for the reply.

I am having trouble understanding GeometryService that you mention. i can't seems to find the latitude, longitude conversion and vice versa.

However, from the samples, I discover that it plots the polygon based on latitude and longitude.

Here is the code:

string polyCoordinate = "2.5,-1 2.5,1 -2.5,1 -2.5,-1 2.5,-1";
ESRI.ArcGIS.Client.Geometry.PointCollectionConverter pointConverter = new ESRI.ArcGIS.Client.Geometry.PointCollectionConverter();
ESRI.ArcGIS.Client.Geometry.PointCollection pointCollection = pointConverter.ConvertFromString(polyCoordinate) as ESRI.ArcGIS.Client.Geometry.PointCollection;

//setup the polygon
Polygon aoi = new Polygon();
aoi.Rings.Add(pointCollection);

BrushConverter brushConv = new BrushConverter();
SimpleFillSymbol symbol = new SimpleFillSymbol();
symbol.BorderBrush = brushConv.ConvertFromString(areaData.Color) as SolidColorBrush;
symbol.BorderThickness = 1;
symbol.Fill = brushConv.ConvertFromString(areaData.FillColor) as SolidColorBrush;

ESRI.ArcGIS.Client.Projection.WebMercator mercator = new ESRI.ArcGIS.Client.Projection.WebMercator();
Graphic polygon = new Graphic();
polygon.Geometry = mercator.FromGeographic(aoi);
polygon.Symbol = symbol;
graphicsLayer.Graphics.Add(polygon);

Each point is based on latitude and longitude value.
However, I got a problem. Firstly, my web will be cached map (downloaded periodically and use offline) and not downloaded realtime.
Is WebMercator still usable?
If WebCator isn't usable, can show me an example on how to convert map point to latitude and longitude and vice versa?

Thanks

[MichaelBranscomb]

Hi,

If you're translating between WGS1984 and Web Mercator Auxiliary Sphere there is a WebMercator class to support this very common case: http://resources.arcgis.com/en/help/runtime-wpf/apiref/index.html?ESRI.ArcGIS.Client~ESRI.ArcGIS.Cli....

Otherwise - for the greatest flexibility you should look at http://resources.arcgis.com/en/help/runtime-wpf/apiref/index.html?ESRI.ArcGIS.Client~ESRI.ArcGIS.Cli....

Cheers

Mike

[StanleyHo]

Thanks for the reply.

I got a question if the cached map (in WebMercator format) is downloaded from the web?
When I take the cache map offline, can I still use the webMercator class to transalte between WGS1984 and webmercator and vice versa?

[MichaelBranscomb · Accepted solution]

Hi,

Yes the WebMercator class is part of the API and therefore will remain alongside your application if it goes "offline". You can also use the LocalGeometryService offline, if you're using the Standard license level.

To use cached maps offline you'll need to create a Tile Package, or take a copy/extract of the server-side cache.

Cheers

Mike

[StanleyHo]

Thanks. I will look into the LocalGeometryService.