Licensing error using offiline viewshed GPK

[ColinWyatt]

I'm getting a licensing error when trying to call a viewshed GPK created in ArcMap Model Builder from Runtime For WPF SDK.

The problem is occuring at the beginning of the geo service call at:
arcpy.CheckOutExtension("spatial")

The Runtime sdk states that the "standard" license includes viewshed 
But I don't know how else to use viewshed except by creating an viewshed geoprocessing package which uses spatial extension! 

What am I missing?
We're using Runtime for WPF 10.2 and have a standard license.

[ColinWyatt]

The error seems to be when I call arcpy.gp.Con_sa(...), because when I remove this part of the model I no longer get the "tool is not licenced error. 
But should this conditional tool be available for Runtime SDK as well?

[KevinHibma · Accepted solution]

Colin,

You'll need the spatial analyst extension as well for those tools.
http://resources.arcgis.com/en/help/runtime-wpf/concepts/index.html#//01700000006r000000

"Spatial Analysis license level tools

The following geoprocessing tools are accessible to apps licensed for the Spatial Analysis extension."