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I'm struggling with a projection question. I have some data in California State Plane and am trying to align a NED with NAD83. I thought these would just natively align, but they don't seem to without project on the fly turned on in QGIS. In ArcMap all is fine, I suppose because project on the fly is working there. This works fine in the end, but when I try to export a raster layer from QGIS/Grass to be used in ArcMap, it projects about 2000 ft off with the data frame set to NAD_1983_StatePlane_California_V_FIPS_0405_Feet.

Any thoughts are greatly appreciated.

Erin

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How are you exporting? E.g., menu Raster->Conversion->Translate –  Scro Nov 15 '12 at 20:04
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Try setting your data frame to match the raster: "GCS_North_American_1983" under Geographic Coordinate Systems. –  Mintx Nov 15 '12 at 20:52
    
I don't think that you can expect them to 'natively align' without project on the fly enabled because they are in two different SRS. They share the same datum, but one SRS has units of degrees and the other SRS has units of feet. –  DavidF Nov 16 '12 at 5:24
    
@Mintx I'm restricted to using the State Plane so it works with other folks' data layers. Setting the data frame to GCS_North_American_1983 distorts the map to a slightly wider form. Thanks tho! –  Erin Nov 16 '12 at 16:33
    
@Scro I'm exporting through the Grass toolbox in QGIS with r.out.arc, maybe this is the problem? It's supposed to create an ESRI ARCGRID file but maybe something happens along the way that I need to account for –  Erin Nov 16 '12 at 23:06
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1 Answer 1

When you export from QGIS, does it create a projection file that is recognizable by ArcMap ( a .prj file)? If the coordinate system of the exported layer is undefined, it will default to projecting on the fly to whatever your data frame is set to. This creates alignment problems if the 2 coordinate systems are different because it does not modify any geometry. The data is projected, you just have to define the projection.

Go to System Toolboxes / Data Management Tools / Projections and Transformations / Define Projection

Or read the help file: http://resources.arcgis.com/en/help/main/10.1/index.html#//001700000077000000

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