GpSHP2gnu given a shapefile (SHP) with full path and the 
	shapefile layer name, the coordinates are saved to a text file readable 
	by gnuplotGpresampleDEM resamples DEM data, similarly to what GIS applications do
GpboxXY returns the box (coordinates) around a location, from a shapefile
GpmapPNG2lines draws "squarish" coastlines given a gridded map from a 
PNG image
Gpmatrix2PNG saves a matrix with a mask of a map to a PNG file
GpplotMap plots a map with vector and raster overlays
GpSHP2gnu(SHPfilename, SHPlayername,gnufilename,toCRS='+init=epsg:4326')
GpresampleDEM(fileIN, fileOUT, xrange, yrange, interpolationMethod, 
XYformat=FALSE)
GpboxXY(fileName)
GpmapPNG2lines(PNGfile, landoutlinefile)
Gpmatrix2PNG(matM,PNGfile)
GpplotMap(mapvectfiles=NA, projection='PlateCarree', linetype='l', 
linestyle=1, plotTitle=NA, maprastfile=NA, maprastpalette=NA, 
AdditionalCode=NA,projectionInit=NA,returnCode=FALSE)Gpmapsr2gnu