CMAQ output and ArcGIS

[steveSuperczynski]

Anyone have any experience opening/viewing/analyzing CMAQ output within ArcGIS. I know that ArcMap has no problems opening the netCDF files and creating rasters from them...the problem I have comes in trying to project the raster based on separate lat/lon rasters.

Disclaimer:  I have very little experience with CMAQ, the files I have were given to me by a colleague who does a lot of modeling with CMAQ.

Thanks,
Steve

[yosukekimura]

m3user mailing list had a post below

IOAPI to NetCDF Conversion Tool for ArcGIS     2012-02-14 14:16:00 <Matthew Russell>

http://lists.unc.edu/read/messages?id=6164053

He distributed an arctoolbox which takes cmaq output (ioapi on netcdf) and adds variables/attributes needed for CF convention that ArcGIS recognizes.

http://resources.arcgis.com/gallery/file/geoprocessing/details?entryID=2FB9C8EE-1422-2418-7FEE-DF5F3...

The toolbox was designed to send data to some website where the processing was performed and then send back a new netcdf file, because the author thought getting the necessary python library may be a hustle for users.  But he included the python code on his website, and the bottom part of code can be uncommented to run it from command line.  so i am using it to convert ioapi/netcdf to cf/netcdf on local machine.

Another thing i still cannot figure out how to resolve is that ArcGIS assumes the projected coordinate uses WGS84 as datum as explained here
http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#//004600000017000000.htm

The CF conventions specifies some elements of the coordinate system but not how to include the geographic coordinate system (datum) portion. Because of this, it is always assumed to be the WGS 1984, whether the data is referenced to a projected or geographic coordinate system. A projected coordinate system is based on a geographic coordinate system and must always be specified. Because of the assumption of WGS 1984, data that is actually referenced to a particular sphere or another spheroid (ellipsoid) may not align with other data layers.

So the converted netcdf file almost shows up where it is supposed to be with Mathew's tool.

[curtvprice]

Another thing i still cannot figure out how to resolve is that ArcGIS assumes the projected coordinate uses WGS84 as datum as explained here
http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#//004600000017000000.htm

The only resolution I know of is to use the Define Projection tool after the raster is imported to redefine to the correct datum (as documented in netCDF tags or in accompanying metadata or readme files).