Comparing spatial references

DaniMaynard — Mon, 04 May 2015 02:40:12 GMT

My app allows a user to choose a shapefile from their computer to load on top of a pre-selected basemap - currently just an ArcGIS Online map service added as a ArcGISDynamicMapServiceLayer. I'm using a FeatureLayer to store the shapefile. What is the best way to determine if the shapefile is of the same spatial reference as the basemap?

My goal is to send a message to the user when their shapefile projection doesn't match the basemap's projection to let them know that the layer will not be added to the map. I can't seem to retrieve the shapefile's spatial reference though when using the "getSpatialReference()" method, even after adding the FeatureLayer to the map. I have tried this with a shapefile that matches the basemap projection, and with a shapefile that doesn't match the basemap projection...the value of the FeatureLayer spatial reference is always null.

The following code:

map.getLayers().add(featureLayer);

System.out.println("Map projection is now: " + map.getSpatialReference());

System.out.println("Layer projection is now: " + featureLayer.getSpatialReference());

System.out.println("Basemap projection is now: " + basemap.getSpatialReference());

...just prints this output:

Map projection is now: SpatialReference [mWKID=102100, mWKT=PROJCS["WGS_1984_Web_Mercator_Auxiliary_Sphere"...

Layer projection is now: null

Basemap projection is now: SpatialReference [mWKID=102100, mWKT=PROJCS["WGS_1984_Web_Mercator_Auxiliary_Sphere"...

I'm just starting to learn the Java API so any help would be appreciated. I haven't found any good examples yet of how to deal with this situation.

Re: Comparing spatial references

OwenEarley — Mon, 04 May 2015 02:48:48 GMT

Have you checked that the shapefile has a spatial reference assigned to it?

A shapefile can happily exist without ever being assigned a spatial reference. This would explain why you get null as a result of the getSpatialReference() call.

Re: Comparing spatial references

DaniMaynard — Mon, 04 May 2015 02:57:32 GMT

My two test shapefiles both have .prj files associated with them. One is simply geographic - GCS_WGS_1984 - and the other is WGS_1984_Web_Mercator_Auxiliary_Sphere (which matches the projection of my basemap).

topic Re: Comparing spatial references in Java Maps SDK Questions

Comparing spatial references

Re: Comparing spatial references

Re: Comparing spatial references