topographic maps

Dear all,

I have a tiny problem, I'd like to draw a map showing topographic information 
(like in a normal atlas) and on top of this map some polygons, points, etc. 
given by long, lat values.

I tried the geomapdata ETOPO5 in conjuction with GEOTOPO which actually works 
fine but the point is I'm dealing with maps displaying Eurasia and this takes 
really time (and memory) to plot [I also set GEOTOPTO's npoints to 5 bustill 
the same].

Then I tried to use geotiff via readOGR which also works but the same here, 
it takes too much time and I have to produce 116 maps.

Well, readGDAL, I hope? If so, use readGDAL(..., output.dim=) to decimate 
the image.

For display, note that the R graphics engines only output vector graphics, 
so each raster cell is drawn as a filled rectangle, which takes time. The 
trick of decimating the image on input ought to reduce the number of 
rectangles to plot.

Roger

Is there any elegant way to have a geo-referenced image as background and 
then to draw polygons etc. on top of it? As I said I'm dealing with Eurasia 
thus the resolution is not the big problem.

I'd be happy to get any hint.

Thanks!

--Hans

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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.Bivand at nhh.no

topographic maps

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