# How can I fix badly specified geographic coordinate system with units in arc-seconds?

Check out this depth-to-rock soil data. It is linked from here. The spatial reference system is a latlon, but the units are arcseconds. I could not reason out how to override the SRS even after staring at this page in the Proj4 wiki for a while and trying to convert the origin coordinates using cs2cs with a +towgs84 argument.

Here's the gdalinfo output for that file:

Driver: E00GRID/Arc/Info Export E00 GRID
Files: rockdepm.e00
Size is 6936, 2984
Coordinate System is:
DATUM["North_American_Datum_1927",
SPHEROID["Clarke 1866",6378206.4,294.978698213898,
AUTHORITY["EPSG","7008"]],
AUTHORITY["EPSG","6267"]],
PRIMEM["Greenwich",0,
AUTHORITY["EPSG","8901"]],
UNIT["degree",0.0174532925199433,
AUTHORITY["EPSG","9108"]],
AUTHORITY["EPSG","4267"]]
Origin = (-449100.000000000000000,177840.000000000000000)
Pixel Size = (30.000000000000000,-30.000000000000000)
Corner Coordinates:
Upper Left  ( -449100.000,  177840.000) (Invalid angle,Invalid angle)
Lower Left  ( -449100.000,   88320.000) (Invalid angle,Invalid angle)
Upper Right ( -241020.000,  177840.000) (Invalid angle,Invalid angle)
Lower Right ( -241020.000,   88320.000) (Invalid angle,Invalid angle)
Center      ( -345060.000,  133080.000) (Invalid angle,Invalid angle)
Band 1 Block=6936x1 Type=Int32, ColorInterp=Undefined
Min=0.000 Max=191.000
Minimum=0.000, Maximum=191.000, Mean=123.286, StdDev=38.233
NoData Value=-2147483647


Notice that the pixel size is 30 arcseconds. If you divide a given set of coordinates by 3600 you get something that makes sense in degrees.

In the course of composing this question I have discovered that the data is available with other SRSs, but in case those are poorly defined as well I thought I would post anyhow.

• You don't really need to reproject it, just georeference it again by resetting the origin and pixel sizes. Would gdal_edit.py work? gdal.org/gdal_edit.html – mkennedy Mar 14 '13 at 23:08
• Sounds promising. I would love to try it, but I don't see gdal_edit or gdal_edit.py in my \$PATH with GDAL 1.9.2 installed. Is that something extra in the source code that is not installed by default, perhaps? – Neil Best Mar 14 '13 at 23:17
• Could be. I just downloaded gdal192.zip and the file's in gdal-1.9.2\swig\python\samples. – mkennedy Mar 14 '13 at 23:54
• @mkennedy, if you want credit for this answer then write it up and I will do my part. I found that the E00GRID driver does not support in-place edits, so I used gdal_translate to create a VRT wrapper and then edited that. – Neil Best Mar 19 '13 at 17:57
• I think you did the actual work! I just pointed out the way. Why don't you write up your solution and accept it? – mkennedy Mar 19 '13 at 18:00