[GIS] reprojecting geotiffs to spherical mercator using gdalwarp

coordinate systemgdal

I would like to reproject raster images (tiffs+proj+tfw) files too "google's" projection using gdalwarp. From what I understand, google uses epsg:900913/epsg:3785.
What I don't know is how to correctly state the source projection.
I believe that UTM32N=epsg:32632. If I reproject using gdalwarp -s_srs epsg:32632 -t_srs:epsg:900913, would that be correct? If I open that file in global mapper, how do I adjust project and worldfile then?

This is the content of my .proj file:

PROJCS["AUT-UTM32N",
GEOGCS["GCS_WGS_1984",
DATUM["D_WGS_1984",SPHEROID["WGS_1984",6378137.0,298.257223563]],
PRIMEM["Greenwich",0.0],
UNIT["Degree",0.0174532925199433]],
PROJECTION["Transverse_Mercator"],
PARAMETER["false_easting",500000.0],
PARAMETER["false_northing",0.0],
PARAMETER["central_meridian",9.0],
PARAMETER["scale_factor",0.9996],
PARAMETER["latitude_of_origin",0.0],

This is the .tfw file:
2.5000000000
0.0000000000
0.0000000000
-2.5000000000
550001.2500000000
5199998.7500000000
UNIT["Meter",1.0]]

Best Answer

The source projection should be read from the file, so you shouldn't have to state it. Try "gdalinfo" on the source file, and if it returns the proper projection, you are all set!

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[GIS] QGIS 1.8.0 – Define shapefile as UTM 15 NAD83 Feet

UTM is always in metres, being internationally standardized. The proj string for UTM 15N is:

+proj=utm +zone=15 +datum=WGS84 +units=m +no_defs

So if your data is in feet, create a custom CRS with this string:

+proj=utm +zone=15 +datum=WGS84 +units=us-ft +no_defs

or look for the NAD83 projections of the US state your data is about.

EDIT: To add a custom CRS:

Settings -> Custom CRS
Click on the yellow star to create a new CRS
Enter a name, like UTM15 ft
paste the proj string in the second line
Click on the save button

[GIS] ArcGIS Desktop, shapefile and EPSG code

If you're not using 10.1, you could create a .prj file with the EPSG-style WKT version (EPSG Geodetic Parameter Dataset has no official WKT format) and place it in the Coordinate Systems, Projected Coordinate Systems folder. Because ArcGIS includes name comparisons when it checks for equality, the WGS 84 definition will not be recognized as equivalent to the GCS_WGS_1984 definition used in the predefined geographic/datum transformations, so you would have to create custom transformation if any are needed.

In 10.1, you can still create a .prj file, but the Coordinate System folder has been removed. Store the file somewhere and use the Import option on the various coordinate system tab or tools to browse and select the file.

Finally, functionally (mathematically), the two definitions are equivalent.

Disclaimer, I guess: I work at Esri and I'm on the subcommittee that maintains the EPSG dataset.

Best Answer

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[GIS] QGIS 1.8.0 – Define shapefile as UTM 15 NAD83 Feet

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