I need to use the AVHRR tree cover classification data available at http://glcf.umd.edu/data/treecover/data.shtml, and so I downloaded the ASCII file for each continent. I have tried all day to import them, but the best I've been able to do is a severely distorted map. The good news is that all continents seem to be distorted the same way. I'll use Africa as an example (ftp://ftp.glcf.umd.edu/glcf/Continuous_Fields_Tree_Cover/Africa/af-latlong-treecover/af-latlong-treecover.grd.gz). Here is the header to the Africa ASCII file: ncols 9955 nrows 9561 xllcorner -26.375000000000 yllcorner -41.500000000000 cellsize 0.008333333333 NODATA_value −9999 (It looks like they actually use 0 instead of −9999 as a missing value.) Here is the script I used for the Africa file… I calculated the endpoints of the axes as endpoint = beginning + (#cells)*0.008333. (You may need to increase available memory.) define axis/X=26.375W:56.584E:0.0083333333/unit=degree xlong define axis/Y=41.5S:38.175N:0.0083333333/unit=degree ylat define grid/X=xlong/Y=ylat defries_africa_grid file/grid=defries_africa_grid/var="TREECOVER"/columns=9955/skip=6 af-latlong-treecover.grd define axis/X=26.375W:56.584E:0.5/unit=degree xlong2 define axis/Y=41.5S:38.175N:0.5/unit=degree ylat2 define grid/X=xlong2/Y=ylat2 defries_af_05grid define variable/title="Defries Africa treecover regridded to 0.5 degree" africa = treecover[d=1,g=defries_af_05grid@ave] save/clobber/file="treecover.nc" africa The result is attached (africa_1.jpg). Playing around with the image reveals that (a) the left border should actually be around where it says 30ºE (i.e., if you cut out everything right of that and paste it onto the left side of what remains, you get something that looks better), (b) it should be flipped vertically (i.e., over the horizontal axis), and [c] that even doing those transformations, it's still pretty distorted (see africa_2.jpg, attached). I've tried several different permutations — including adding order=yx into the fourth command — but they all ended up looking worse. This may be an issue with the dataset, but I'm more willing to believe the error lies with this end-user. Thanks in advance. Sam Rabin Graduate student Princeton University Ecology & Evolutionary Biology |