Overlaying OneMap onto ESRI map

Question

How do I overlay a map(OneMap) over an ESRI map? It is possible as shown in the url below. There are many layers that can be overlaid onto the ESRI map and even OneMap basemap, what methods can I use to overlay the basemap (http://www.onemap.sg/ArcGIS/rest/services/BASEMAP/MapServer) onto ESRI map?

url: http://www.arcgis.com/home/webmap/viewer.html?useExisting=1

ManishkumarPatel · Answer

Hi Chu Cheuk Yiu,

The difference in the projection of the One Map map service and ESRI will not allow it to add as a basemap or feature layer.

Since One Map is using SVY21 projection what you can do is overlay the onemap as an ArcGISDynamicMapServiceLayer on top of the ESRI basemap. Althought if you add One Map as dynamic map service layer it will not adhere to the One Map scales and display map projection as the esri basemap projection.

Another option is that you will need to write your own custom function to handle the change of the basemaps where in you will need destroy and create the map again and then add any basemap as per requirement. In this case the map projection will adhere to the One Map projection.

map.destroy();
map = new map("mapdiv");

Hope this helps.

Regards,
Manish Patel

AntGiles · Answer

I can get an esri base map to overlay on top of onemap but it does not work the other way round I think it may be a projection problem, try the following code in the javascript sandbox: http://developers.arcgis.com/javascript/sandbox/sandbox.html Simple Map

Regards Anthony

AntGiles · Answer

Are you sure the Singapore map is in the same projection as the basemaps (i.e Web Mercator). If you watch the network traffic when using the online viewer the call to the Singapore map is different to the call to the normal basemaps, see attached

Regards

Anthony

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