Yes, buffer distances can be smoothly calculated using SAGA (I do not if it will work for your HUGE image, but you can try). Here is an example:
......... # Import the contour data (from the 1:5k and 1:50k topo maps): > library(maptools) > getinfo.shape("contours.shp") > contours.50 <- readShapeLines("contours.shp", > proj4string=CRS(as.character(NA))) > contours.5 <- readShapeLines("contours2.shp", > proj4string=CRS(as.character(NA))) # estimate the initial cell size based on the spacing between the contours: dem.area <- ([EMAIL PROTECTED],[EMAIL PROTECTED],1])*([EMAIL PROTECTED],[EMAIL PROTECTED],1]) # for beginning, we take a cell size that corresponds to the effective scale: dem.pixelsize <- 25 # estimate the buffer distance between the contour lines library(RSAGA) # Download SAGA GIS from www.saga-gis.org and unzip the binaries to: rsaga.env(path="C:/Program Files/saga_vc") # first, convert the contour map to a raster map: rsaga.geoprocessor(lib="grid_gridding", module=3, param=list(GRID="contour50_buff.sgrd", INPUT="contours.shp", FIELD=1, LINE_TYPE=0, USER_CELL_SIZE=dem.pixelsize, [EMAIL PROTECTED],1], [EMAIL PROTECTED],2], [EMAIL PROTECTED],1], [EMAIL PROTECTED],2])) # now extract a buffer distance map (for 'contours') and load it back to R: # the parameters DIST and IVAL are estimated based on the grid properties: rsaga.geoprocessor(lib="grid_tools", module=10, param=list(SOURCE="contour50_buff.sgrd", DISTANCE="contours50_dist.sgrd", ALLOC="contours50_alloc.sgrd", BUFFER="contours50_bdist.sgrd", DIST=sqrt(dem.area)/3, IVAL=dem.pixelsize)) rsaga.sgrd.to.esri(in.sgrds="contours50_dist.sgrd", out.grids="contours50_dist.asc", out.path=getwd(), prec=1) contours50.dist <- readGDAL("contours50_dist.asc") ......... and the complete sample R script: http://spatial-analyst.net/PIXEL/pixelR.zip cheers, Tom Hengl http://spatial-analyst.net -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of milton ruser Sent: maandag 21 juli 2008 21:11 To: r-sig-geo@stat.math.ethz.ch Subject: [R-sig-Geo] generating distance map for Large map Dear all, I have a very large BINARY image (60,000x50,000 pixels) and need to generate the distance map from the 1 values. When the images are small than my image, I can generate the distance map using ArcGis (my image is in .IMG format), but ArcGis return error for this large one. I am running R 2.7.1 under windows/xp. Is there a way of do this job using R ou RSaga? (unfortunately I don´t have GRASS installed), and my experience with RSAGA is near zero. My computer is 4GB ram. I can load the images on ArcGis and Erdas without problem, but I only don´t know how do this task. Sorry for not send a reproducible code. Any help are welcome. Miltinho Astronauta Brazil [[alternative HTML version deleted]] _______________________________________________ R-sig-Geo mailing list R-sig-Geo@stat.math.ethz.ch https://stat.ethz.ch/mailman/listinfo/r-sig-geo