GeoTiff Raster Projection bug on export?
GeorgeP
Global Mapper User
I am trying to export a raster image using the current projection as defined in Configure. It is set to State Plane, the Appropriate Zone, NAD83, Units Feet. When I import the GeoTiff into Mapinfo it is reading the exported units as meters instead of feet (but the numeric values are still feet). What am I missing? It appears Global Mapper is not writing the header correctly.
Contents of the .TAB created when you import the geotif are as follows:
!table
!version 300
!charset WindowsLatin1
Definition Table
File "quads_shaded_3.tif"
Type "RASTER"
(2380605.4997526626,1475650.1976429506) (0,0) Label "Pt 1",
(2481141.2864726977,1475650.1976429506) (12601,0) Label "Pt 2",
(2380605.4997526626,1362524.4996901392) (0,14179) Label "Pt 3"
CoordSys Earth Projection 8, 74, "m", -110.0833333333, 40.5, 0.9999375, 800000, 100000
Units "m"
Contents of the .TAB created when you import the geotif are as follows:
!table
!version 300
!charset WindowsLatin1
Definition Table
File "quads_shaded_3.tif"
Type "RASTER"
(2380605.4997526626,1475650.1976429506) (0,0) Label "Pt 1",
(2481141.2864726977,1475650.1976429506) (12601,0) Label "Pt 2",
(2380605.4997526626,1362524.4996901392) (0,14179) Label "Pt 3"
CoordSys Earth Projection 8, 74, "m", -110.0833333333, 40.5, 0.9999375, 800000, 100000
Units "m"
Comments
-
If you load the GeoTIFF file into Global Mapper is the projection correct? Which state plane zone are you using? There are some that are defined by their states to use particular units so it's possible that MapInfo is ignoring the units specified in the GeoTIFF file and using that mandated by the state. Or it's possible Global Mapper is saving it wrong. What version of Global Mapper are you using?
Thanks,
Mike
Global Mapper Guru
gmsupport@bluemarblegeo.com
http://www.globalmapper.com -
If I load the geotiff back into Global Mapper yes, it comes in as the correct projection - State Plane, Feet. I'm using Wyoming West zone (FIPS 4904) Global Mapper v 14.0.
Thanks.
-Georgge -
George,
It does indeed sound like a MapInfo problem. That zone is specified to use meters by default, so MapInfo is likely ignoring the specified units and using the legally mandated default of meters. If you set your projection to meters in Global Mapper prior to export does that work fine when using it in MapInfo?
Thanks,
Mike
Global Mapper Guru
gmsupport@bluemarblegeo.com
http://www.globalmapper.com -
I can export from global mapper setting units to Meters and it imports into Mapinfo in the correct geographic location.
It's interesting because typically Mapinfo will bring up a dialog to allow you to specify the projection when opening anything that does not already have a .TAB file. It's reading the GeoTIFF header and opening it directly. Out of curiosity I tried exporting from GM without the header info being written but then Mapinfo makes you re-register the image from scratch - makes sense. I will use MI to reproject from meters to feet.
Thanks for looking into it.
-George
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