Extent and coordinate system

04-01-2010 08:44 AM
Status: Open
MVP Esteemed Contributor

Geoprocessing is pretty nifty working across coordinate systems, but with raster processing there is a hassle with extents and coordinate systems. If you define the extent from a dataset in one coordinate system and try to use it processing in another coordinate system, you reap nothing because the extent is defined in a different coordinate system than the data. The only solution is to project your extent data set before you use it.

It would be nice to have the ability for the gp to smart-project extents when specifying data sets (with a warning of course, as the results may be strange if the two coordinate systems are significantly different). (Could an inversability statistic by reported  in the error message - then you'd know whether this was a reasonable on the fly projection to use.)

Here's an illustration of what I'm talking about:

>>> arcpy.OutputCoordinateSystem = "UTMBox"
>>> arcpy.Extent = "e:\\work\\albersbox"
WARNING: Extent was projected to match output coordinate system

This wouldn't be doable for cell size or snap, as these depend on location, which you wouldn't know. But supporting on the fly extent projection would be a useful addition to this functionality.

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