[GRASS-user] importing geotif in grass, transformation parameters

[Paul Kelly]

On Tue, 24 Jun 2008, Martina Schaefer wrote:

> Hi Paul,
>
> here the infos that you asked me for:
[...]
> in fact, this is the same data as the following one, only transformed to 
> LatLong by ArcGIS
>
> GRASS 6.2.2 (BelcherBathy):~/Work/Devon-Data/bthy > gdalinfo 00005_utm.tif
> Driver: GTiff/GeoTIFF
> Size is 14805, 2508
> Coordinate System is:
> PROJCS["WGS 84 / UTM zone 17N",
>    GEOGCS["WGS 84",
>        DATUM["WGS_1984",
>            SPHEROID["WGS 84",6378137,298.2572235630016,
>                AUTHORITY["EPSG","7030"]],
>            AUTHORITY["EPSG","6326"]],
>        PRIMEM["Greenwich",0],
>        UNIT["degree",0.0174532925199433],
>        AUTHORITY["EPSG","4326"]],
>    PROJECTION["Transverse_Mercator"],
>    PARAMETER["latitude_of_origin",0],
>    PARAMETER["central_meridian",-81],
>    PARAMETER["scale_factor",0.9996],
>    PARAMETER["false_easting",500000],
>    PARAMETER["false_northing",0],
>    UNIT["metre",1,
>        AUTHORITY["EPSG","9001"]],
>    AUTHORITY["EPSG","32617"]]
> Origin = (490944.258245616627391,8409263.051821239292622)
> Pixel Size = (1.414845022256486,-5.571261774748564)
> Metadata:
>  AREA_OR_POINT=Area
>  TIFFTAG_SOFTWARE=IMAGINE TIFF Support
> Copyright 1991 - 1999 by ERDAS, Inc. All Rights Reserved
> @(#)$RCSfile: etif.c $ $Revision: 1.9.1.3 $ $Date: 2002/07/29 15:39:06EDT $
>  TIFFTAG_XRESOLUTION=1
>  TIFFTAG_YRESOLUTION=1
>  TIFFTAG_RESOLUTIONUNIT=2 (pixels/inch)
> Image Structure Metadata:
>  COMPRESSION=LZW
> Corner Coordinates:
> Upper Left  (  490944.258, 8409263.052)
> Lower Left  (  490944.258, 8395290.327)
> Upper Right (  511891.039, 8409263.052)
> Lower Right (  511891.039, 8395290.327)
> Center      (  501417.649, 8402276.690)
> Band 1 Block=14805x1 Type=Byte, ColorInterp=Red
> Band 2 Block=14805x1 Type=Byte, ColorInterp=Green
> Band 3 Block=14805x1 Type=Byte, ColorInterp=Blue
> Band 4 Block=14805x1 Type=Byte, ColorInterp=Undefined

If you run
g.proj -c georef=filename
where filename is the name of the file that contains the correct 
co-ordinate system info, it will overwrite the current location's 
projection with the correct values. Although only do this if you are sure 
the projection is definitely correct, and not just a default value that 
the other software added into the file.

Add the -i flag as well as -c if you want to be interactively prompted for 
datum parameters (with some hints on which ones to pick).

Hope this helps a bit

Paul