On Mon, 4 Jan 2010, Peter Adler wrote:
Dear R-sig-geo,
I am new to RGDAL and PROJ4, and am having trouble projecting a raster
dataset.
The dataset is a 721 x 721 cell raster of snow cover from the NSIDC. The
projection information is here:
http://nsidc.org/data/atlas/epsg_3408.html
My command:
D=readGDAL("annual_snow_trend_ease.tif",
p4s="+proj=laea +lat_0=90 +lon_0=0 +x_0=0 +y_0=0 +a=6371228 +b=6371228
+units=m +no_defs")
gets executed, but is followed by the warning message:
annual_snow_trend_ease.tif has GDAL driver GTiff
and has 721 rows and 721 columns
Warning message:
In readGDAL("annual_snow_trend_ease.tif", p4s = "+init=epsg:3408") :
GeoTransform values not available
The message is not related to the projection, but to the underlying
dimensions of the image - it is being read as a 721 by 721 picture, with
no location of the NW cell, and no cell sizes. This rather suggests that
the Tiff file is not a GeoTiff, otherwise these values should have been
present. Are you using the "browse image files" rather than the snow cover
data (I don't think so)? Omit the p4s= value, and report summary() of the
imported object - I think you'll see that it has coordinates 0-721 in each
dimension or some such.
Roger
Using:
D=readGDAL("annual_snow_trend_ease.tif",
p4s="+init=epsg:3408")
gives the same result.
I am running R 2.10 on a Windows Vista machine. I think I have all the
required libraries installed. When I load rgdal, I see:
Loading required package: sp
Geospatial Data Abstraction Library extensions to R successfully loaded
Loaded GDAL runtime: GDAL 1.6.2, released 2009/07/31
Path to GDAL shared files: C:/PROGRA~1/R/R-210~1.0/library/rgdal/gdal
Loaded PROJ.4 runtime: Rel. 4.6.1, 21 August 2008
Path to PROJ.4 shared files: C:/PROGRA~1/R/R-210~1.0/library/rgdal/proj
Thanks for your help,
Peter
-- Peter Adler Dept. of Wildland Resources and the Ecology Center 5230 Old
Main Utah State University Logan, UT 84322 tel: (435) 797-1021 email:
peter.ad...@usu.edu http://www.cnr.usu.edu/htm/facstaff/adler-web
--
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Helleveien 30, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: roger.biv...@nhh.no
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