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Raster Geoprocessing dilemma (obtaining Cell Value)

03-05-2013 07:56 AM
Frequent Contributor
I think I've painted myself into a corner and I'm not sure how to get what I want.

I'm developing a web application which will utilize NWS weather radar images as an overlay option. The images are always being refreshed but are only accessible as GIF files. Within my app, I'm pulling in these images directly from the NWS and adding them into my map as a mapImageLayer and they work great. The problem is that this layer type does not support an identify/query on the pixel values.

I thought a possible workaround was to publish the "Get Cell Value" tool from ArcToolBox (Data Management->Raster->Raster Properties) as a geoprocessing service and then pass the URL of my radar image to query the values. My GP service actually works but always returns NoData because the GIF files as provided by the NWS do not have embedded georeferenced information. That information *IS* known and can be put into a world file but the GP service doesn't see it when the input raster is from a remote location (hence the NoData values). I tested this theory by passing a local network copy of the file complete with world file to my GP service and it returned a valid value.

So- the trick is how can I supply that spatial reference for an image I'm not hosting so that the GP task recognizes it and returns a proper value? I don't know if this is possible but the only thing I could come up with was to "pause" processing after the scratch workspace was established and then add the world file for the image into the workspace and continue the GP process.

This would be SOOOO much easier if the JS API just supported identify/queryTasks on mapImageLayers. Oh well.

Anyone have ideas?

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