topic Identify on Raster Values in ArcGIS JavaScript Maps SDK Questions

Identify on Raster Values

JohnBocan — Mon, 18 Mar 2013 14:42:55 GMT

Question: Is it possible to get the pixel value of a raster layer in a MapService using the Identify feature? I've looked a bit in the forums and didn't see much on this or similar questions were left unanswered. I am using Javascript 3.3 and I'm pulling a MapService from ArcGIS Server 10.1--specifically: http://atlas.wvgs.wvnet.edu/arcgis/rest/services/Coal_Web_Mercator/Pittsburgh_WM/MapServer where I'd like to pull from raster layers 6, 10, 14, 22 which deals with coal elevation and thickness. I'm using the Find-Drilldown Identify tool (http://help.arcgis.com/en/webapi/javascript/arcgis/jssamples/find_drilldown.html) in my application. I was able to employ it successfully with the vector layers.

I'd appreciate some direction in this matter.

Regards,
John Bocan
GIS Programmer/Analyst
WVGES

Re: Identify on Raster Values

StephenLead — Mon, 18 Mar 2013 22:52:06 GMT

You could try using a queryTask instead of identify.

You may need to run multiple queryTasks (one for each layer you wish to run against, ie http://atlas...../MapServer/6, http://atlas..../MapServer/10, etc)

Brett Lord-Castillo put together a demo showing how to run multiple query tasks concurrently at http://jsfiddle.net/blordcastillo/mULcz/

Re: Identify on Raster Values

JohnBocan — Tue, 19 Mar 2013 20:09:10 GMT

Thanks for the suggestion. I will consider that query solution instead of the identify drilldown idea for my application (seems cleaner and more efficient!); however, it does not answer my main problem--apprehending the pixel value of a raster layer in a MapService and then displaying the value. Both the identify and query means of showing data deal with "fields". Rasters only have a "value" or "pixel value" and I've not found a good discussion on querying or identifying those in a MapService. Any direction to further documentation or suggestions is greatly appreciated!

Re: Identify on Raster Values

SteveCole — Tue, 19 Mar 2013 20:21:41 GMT

This thread might be some help. It seems to suggest that the syntax for retrieving a pixel value might be:

idResults[0]['Pixel Value']

Haven't tried it so I'm just throwing it out there.

Steve