Changes between Version 1 and Version 2 of UserDocs/GdalTranslate

Timestamp:

May 22, 2007, 11:25:36 AM (17 years ago)

Author:

maphew

Comment:

added Syntax for PROJ4 section

UserDocs/GdalTranslate

@@ -2 +2 @@
   ''The official documentation for the `gdal_translate` utility is http://www.gdal.org/gdal_translate.html.''
 
-'''when to use `-a_ullr`''' - ''Assign/override the georeferenced bounds of the output file.''
+=== When to use `-a_ullr` === 
+  ''Assign/override the georeferenced bounds of the output file.''
 
 Use the `-a_ullr` option to add coordinates and pixel size to your raster. Using `-a_srs` alone only adds information about coordinate system without modifying the coordinates themselves ( i.e. upper-left coordinates, pixel size and so on). So if the source image doesn't provide this information to gdal they need to be added by hand.
+
+== Syntax for PROJ.4 parameters ==
+
+In trying to use the gdal_translate on a non-standard projection, the hardest part is often to determine what the allowable syntax and meaning of the PROJ.4 parameters were (i.e. `+lat_0=70, +ellps=WGS84`) as an argument to `-a_srs, -t_srs, -s_srs`. There is no clean ready made list, however the [http://www.remotesensing.org/geotiff/proj_list/ GeoTIFF projections transform list] is a great start. Find the page for the projection you need and scan for the '''''PROJ.4 Organization''''' heading. 
+
+For example this Arcinfo projection: 
+{{{
+Projection    ALBERS
+Datum         NAD83
+Zunits        NO
+Units         METERS
+Spheroid      GRS1980
+Xshift        0.0000000000
+Yshift        0.0000000000
+Parameters
+61 40  0.000 /* 1st standard parallel
+68  0  0.000 /* 2nd standard parallel
+-132 30  0.000 /* central meridian
+59  0  0.000 /* latitude of projection's origin
+500000.00000 /* false easting (meters)
+500000.00000 /* false northing (meters)
+}}}
+
+Becomes this in PROJ4 [http://www.remotesensing.org/geotiff/proj_list/albers_equal_area_conic.html *]:
+{{{
++proj=aea +lat_1=61.66666666666666 +lat_2=68.0 +lat_0=59.0 +lon_0=-132.5 
++x_0=500000 +y_0=500000 +ellps=GRS80 +datum=NAD83 +units=m
+}}}
+
+If it is a projection you use a lot, write it to a text file and refer to it like this:
+
+{{{ gdal_translate ... -t_srs z:\common\yt-albers.proj4 ... infile.tif outfile.tif }}}
+
+