Roger Bivand (with the help of Volker Wichmann, Frank Warmerdam and Johan Van de Wauw) have just released the new development version of the rgdal package which now includes SAGA GIS Binary Grid (.sdat) driver. To install the packages use (the development version will soon be put on CRAN):
> download.file("http://spatial.nhh.no/R/Devel/rgdal_0.6-23.zip", destfile=paste(getwd(), "rgdal_0.6-23.zip", sep="/")) trying URL 'http://spatial.nhh.no/R/Devel/rgdal_0.6-23.zip' Content type 'application/zip' length 7958270 bytes (7.6 Mb) opened URL downloaded 7.6 Mb > install.packages("rgdal_0.6-23.zip", repos = NULL) package 'rgdal' successfully unpacked and MD5 sums checked updating HTML package descriptions
then load the library in your R session:
> library(rgdal) Geospatial Data Abstraction Library extensions to R successfully loaded Loaded GDAL runtime: GDAL 1.7.0dev, released 2008/11/26 Path to GDAL shared files: C:/PROGRA~2/R/R-29~1.2/library/rgdal/gdal Loaded PROJ.4 runtime: Rel. 4.6.1, 21 August 2008 Path to PROJ.4 shared files: C:/PROGRA~2/R/R-29~1.2/library/rgdal/proj Warning message: package 'rgdal' was built under R version 2.10.0
The short driver name is:
> getGDALDriverNames()[71,] name long_name create copy 71 SAGA SAGA GIS Binary Grid (.sdat) TRUE TRUE
To write to SAGA grid, use:
# Load the data: > data(meuse.grid) > coordinates(meuse.grid) <- ~x+y > gridded(meuse.grid) <- TRUE > fullgrid(meuse.grid) <- TRUE > writeGDAL(meuse.grid["dist"], "meuse_dist.sdat", drivername="SAGA")
which will create two files: (1) the header file (*.sgrd) and (2) the binary file (*.sdat). To check that everything is ok, run:
> file.show("meuse_dist.sgrd") NAME = meuse_dist DESCRIPTION = UNIT = DATAFILE_OFFSET = 0 DATAFORMAT = FLOAT BYTEORDER_BIG = FALSE POSITION_XMIN = 178460.0000000000 POSITION_YMIN = 329620.0000000000 CELLCOUNT_X = 78 CELLCOUNT_Y = 104 CELLSIZE = 40.0000000000 Z_FACTOR = 1.000000 NODATA_VALUE = -1.000000 TOPTOBOTTOM = FALSE
To read SAGA grids to R, use:
> meuse.sgrd <- readGDAL("meuse_dist.sdat") meuse_dist.sdat has GDAL driver SAGA and has 104 rows and 78 columns