initGRASS <- function(gisBase, home, SG, gisDbase, location, mapset,
    override=FALSE) {
    if (nchar(Sys.getenv("GISRC")) > 0 && !override)
      stop("A GRASS location is already in use; to override, set override=TRUE")

    SYS <- get("SYS", envir=.GRASS_CACHE) 
    if (SYS == "WinNat") {
# grass63.bat
        Sys.setenv(GRASSDIR=gisBase)
        if (missing(home)) home <- Sys.getenv("USERPROFILE")
        Sys.setenv(HOME=home)
        Sys.setenv(WINGISBASE=Sys.getenv("GRASSDIR"))
        Sys.setenv(GRASS_PROJSHARE=paste(Sys.getenv("GRASSDIR"),
            "\\proj", sep=""))
        Sys.setenv(GRASS_SH=paste(Sys.getenv("GRASSDIR"), 
            "\\msys\\bin\\sh.exe", sep=""))
        Wpath <- Sys.getenv("PATH")
        if (length(grep(basename(Sys.getenv("GRASSDIR")), Wpath)) < 1) {
            Sys.setenv(PATH=paste(Sys.getenv("GRASSDIR"), "\\msys\\bin;", 
                Sys.getenv("PATH"), sep=""))
            Sys.setenv(PATH=paste(Sys.getenv("GRASSDIR"), "\\extrabin;",
                Sys.getenv("GRASSDIR"), "\\extralib;",
                Sys.getenv("PATH"), sep=""))
            Sys.setenv(PATH=paste(Sys.getenv("GRASSDIR"), "\\tcl-tk\\bin;",
                Sys.getenv("GRASSDIR"), "\\sqlite\\bin;",
                Sys.getenv("GRASSDIR"), "\\gpsbabel;", 
                Sys.getenv("PATH"), sep=""))
# etc/Init.bat
            GRASS_addons <- Sys.getenv("GRASS_ADDON_PATH")
            if (GRASS_addons == "")
                Sys.setenv(PATH=paste(Sys.getenv("WINGISBASE"), "\\bin;",
                    Sys.getenv("WINGISBASE"), "\\lib;",
                    Sys.getenv("PATH"), sep=""))
            else 
                Sys.setenv(PATH=paste(Sys.getenv("WINGISBASE"), "\\bin;",
                    Sys.getenv("WINGISBASE"), "\\lib;",
                    GRASS_addons, ";", Sys.getenv("PATH"), sep=""))
        }
        Sys.setenv(WINGISRC=paste(Sys.getenv("HOME"), "\\.grassrc6", sep=""))
        if (file.exists(Sys.getenv("WINGISRC")) && !override)
            stop("A GISRC file already exists; to override, set override=TRUE")
        Sys.setenv(GISRC="junk")
        cat("GISDBASE:", getwd(), "\n", file=Sys.getenv("WINGISRC"))
        cat("LOCATION_NAME: <UNKNOWN>", "\n", file=Sys.getenv("WINGISRC"),
            append=TRUE)
        cat("MAPSET: <UNKNOWN>", "\n", file=Sys.getenv("WINGISRC"),
            append=TRUE)
        gisrc <- system(paste("g.dirseps.exe -g",
            shQuote(Sys.getenv("WINGISRC"))), intern=TRUE)
        assign("addEXE", .addexe(), envir=.GRASS_CACHE)
        Sys.setenv(GISRC=gisrc)
        if (!missing(gisDbase)) {
            dir.create(gisDbase)
        } else gisDbase <- tempdir()
        gisDbase <- system(paste("g.dirseps.exe -g",
            shQuote(gisDbase)), intern=TRUE)
    } else if (SYS == "unix") {
        Sys.setenv(GISBASE=gisBase)
        if (missing(home)) home <- Sys.getenv("HOME")
        ePATH <- Sys.getenv("PATH")
        if (length(grep(basename(Sys.getenv("GISBASE")), ePATH)) < 1) {
            Sys.setenv(PATH=paste(Sys.getenv("PATH"), ":", 
            Sys.getenv("GISBASE"), "/bin:", Sys.getenv("GISBASE"),
            "/scripts", sep=""))
        }
        eLDPATH <- Sys.getenv("LD_LIBRARY_PATH")
        if (length(grep(basename(Sys.getenv("GISBASE")), eLDPATH)) < 1) {
            Sys.setenv(LD_LIBRARY_PATH=paste(Sys.getenv("LD_LIBRARY_PATH"),
                ":", Sys.getenv("GISBASE"), "/lib", sep=""))
        }
        Sys.setenv(GISRC=paste(home, "/.grassrc6", sep=""))
        if (file.exists(Sys.getenv("GISRC")) && !override)
            stop("A GISRC file already exists; to override, set override=TRUE")
        if (!missing(gisDbase)) {
            dir.create(gisDbase)
        } else gisDbase <- tempdir()
        cat("GISDBASE:", gisDbase, "\n", file=Sys.getenv("GISRC"))
        cat("LOCATION_NAME: <UNKNOWN>", "\n", file=Sys.getenv("GISRC"),
            append=TRUE)
        cat("MAPSET: <UNKNOWN>", "\n", file=Sys.getenv("GISRC"),
            append=TRUE)
    } else stop(paste("Platform variant", SYS, "not supported"))
    system(paste(paste("g.gisenv", get("addEXE", envir=.GRASS_CACHE), sep=""),
        shQuote(paste("set=GISDBASE=", gisDbase))))
    if (missing(location)) location <- basename(tempfile())
    loc_path <- paste(gisDbase, location, sep="/")
    dir.create(loc_path)
    if (!file.exists(paste(loc_path, "PERMANENT", sep="/")))
        dir.create(paste(loc_path, "PERMANENT", sep="/"))
    if (missing(mapset)) mapset <- basename(tempfile())
    if (!file.exists(paste(loc_path, mapset, sep="/")))
        dir.create(paste(loc_path, mapset, sep="/"))
    system(paste(paste("g.gisenv", get("addEXE", envir=.GRASS_CACHE), sep=""),
        shQuote(paste("set=GISDBASE", gisDbase, sep="="))))
    system(paste(paste("g.gisenv", get("addEXE", envir=.GRASS_CACHE), sep=""),
        shQuote(paste("set=LOCATION_NAME", location, sep="="))))
    system(paste(paste("g.gisenv", get("addEXE", envir=.GRASS_CACHE), sep=""),
        shQuote(paste("set=MAPSET", mapset, sep="="))))
    system(paste(paste("g.gisenv", get("addEXE", envir=.GRASS_CACHE), sep=""),
        shQuote("set=GRASS_GUI=text")))
    Sys.setenv(GISBASE=gisBase)
    Sys.setenv(GISDBASE=gisDbase)
    Sys.setenv(LOCATION_NAME=location)
    Sys.setenv(MAPSET=mapset)
    pfile <- paste(loc_path, "PERMANENT", "DEFAULT_WIND", sep="/")
    if (!file.exists(pfile)) {
        mSG <- !missing(SG)
        if (mSG) bb <- bbox(SG)
        if (mSG) gt <- gridparameters(SG)
        cat("proj:       0\n", file=pfile)
        cat("zone:       0\n", file=pfile, append=TRUE)
        cat("north:      ", ifelse(mSG, bb["y", "max"], 1), "\n",
            sep="", file=pfile, append=TRUE)
        cat("south:      ", ifelse(mSG, bb["y", "min"], 0), "\n",
            sep="", file=pfile, append=TRUE)
        cat("east:       ", ifelse(mSG, bb["x", "max"], 1), "\n",
            sep="", file=pfile, append=TRUE)
        cat("west:       ", ifelse(mSG, bb["x", "min"], 0), "\n",
            sep="", file=pfile, append=TRUE)
        cat("cols:       ", ifelse(mSG, gt$cells.dim[1], 1), "\n",
            sep="", file=pfile, append=TRUE)
        cat("rows:       ", ifelse(mSG, gt$cells.dim[2], 1), "\n",
            sep="", file=pfile, append=TRUE)
        cat("e-w resol:  ", ifelse(mSG, gt$cellsize[1], 1), "\n",
            sep="", file=pfile, append=TRUE)
        cat("n-s resol:  ", ifelse(mSG, gt$cellsize[2], 1), "\n",
            sep="", file=pfile, append=TRUE)
        cat("top:        1\n", sep="", file=pfile, append=TRUE)
        cat("bottom:     0\n", sep="", file=pfile, append=TRUE)
        cat("cols3:      ", ifelse(mSG, gt$cells.dim[1], 1), "\n",
            sep="", file=pfile, append=TRUE)
        cat("rows3:      ", ifelse(mSG, gt$cells.dim[2], 1), "\n",
            sep="", file=pfile, append=TRUE)
        cat("depths:     1\n", sep="", file=pfile, append=TRUE)
        cat("e-w resol3: ", ifelse(mSG, gt$cellsize[1], 1), "\n",
            sep="", file=pfile, append=TRUE)
        cat("n-s resol3: ", ifelse(mSG, gt$cellsize[2], 1), "\n",
            sep="", file=pfile, append=TRUE)
        cat("t-b resol:  1\n", sep="", file=pfile, append=TRUE)
    }
    tfile <- paste(loc_path, "PERMANENT", "WIND", sep="/")
    if (!file.exists(tfile)) file.copy(pfile, tfile, overwrite=TRUE)
    tfile <- paste(loc_path, mapset, "WIND", sep="/")
    if (!file.exists(tfile)) file.copy(pfile, tfile, overwrite=TRUE)
    gmeta6()
}