R - gdalUtils - gdal_grid example data giving zero values...? - r

Question

I have been trying to use the gdal_grid in R and while running the example data set I recieve a raster which has only zero values. I have tried experimenting with this with my own data, and have searched the forums with no luck. Can others get the example to work?
I have tried to explicitly call my path to my GDAL library, and have updated the version of GDAL. I am running R studio with version 3.3.1.
library(raster)
library(rgeos)
library(gdalUtils)
# We'll pre-check to make sure there is a valid GDAL install
# and that raster and rgdal are also installed.
# Note this isn't strictly neccessary, as executing the function will
# force a search for a valid GDAL install.
gdal_setInstallation()
valid_install <- !is.null(getOption("gdalUtils_gdalPath"))
if(require(raster) && valid_install)
{
# Create a properly formatted CSV:
temporary_dir <- tempdir()
tempfname_base <- file.path(temporary_dir,"dem")
tempfname_csv <- paste(tempfname_base,".csv",sep="")
pts <- data.frame(
Easting=c(86943.4,87124.3,86962.4,87077.6),
Northing=c(891957,892075,892321,891995),
Elevation=c(139.13,135.01,182.04,135.01)
)
write.csv(pts,file=tempfname_csv,row.names=FALSE)
# Now make a matching VRT file
tempfname_vrt <- paste(tempfname_base,".vrt",sep="")
vrt_header <- c(
'<OGRVRTDataSource>',
'\t<OGRVRTLayer name="dem">',
'\t<SrcDataSource>dem.csv</SrcDataSource>',
'\t<GeometryType>wkbPoint</GeometryType>',
'\t<GeometryField encoding="PointFromColumns" x="Easting" y="Northing" z="Elevation"/>',
'\t</OGRVRTLayer>',
'\t</OGRVRTDataSource>'
)
vrt_filecon <- file(tempfname_vrt,"w")
writeLines(vrt_header,con=vrt_filecon)
close(vrt_filecon)
tempfname_tif <- paste(tempfname_base,".tiff",sep="")
# Now run gdal_grid:
setMinMax(gdal_grid(src_datasource=tempfname_vrt,
dst_filename=tempfname_tif,a="invdist:power=2.0:smoothing=1.0",
txe=c(85000,89000),tye=c(894000,890000),outsize=c(400,400),
of="GTiff",ot="Float64",l="dem",output_Raster=TRUE))
}
r<-raster(tempfname_tif)
r
#class : RasterLayer
#dimensions : 400, 400, 160000 (nrow, ncol, ncell)
#resolution : 10, 10 (x, y)
#extent : 85000, 89000, 890000, 894000 (xmin, xmax, ymin, ymax)
#coord. ref. : NA
#data source : C:\Users\m.modeler\AppData\Local\Temp\RtmpW6HvOc\dem.tiff
#names : dem
#min values : 0
#max values : 0
plot(r)
Raster results plot with zero values:
Thanks much,

Answer 1

I have got the code to run by changing the path from the temp directory to a folder on my hard drive. Example below.
# change to a path on your computer
setwd("C:\\Users\\m.modeler\\Documents\\R\\gdal_Examples")
#######################################################
#create XYZ csv
pts <- data.frame(
Easting=c(86943.4,87124.3,86962.4,87077.6),
Northing=c(891957,892075,892321,891995),
Elevation=c(139.13,135.01,182.04,135.01))
write.csv(pts,file="dem.csv",row.names=FALSE)
#######################################################
#create VRT
fn_vrt<-"dem.vrt"
# Now make a matching VRT file
vrt_header <- c(
'<OGRVRTDataSource>',
'\t<OGRVRTLayer name="dem">',
'\t<SrcDataSource>dem.csv</SrcDataSource>',
'\t<GeometryType>wkbPoint</GeometryType>',
'\t<GeometryField encoding="PointFromColumns" x="Easting" y="Northing" z="Elevation"/>',
'\t</OGRVRTLayer>',
'\t</OGRVRTDataSource>')
vrt_filecon <- file(fn_vrt,"w")
writeLines(vrt_header,con=vrt_filecon)
close(vrt_filecon)
#######################################################
#create interpolated DEM
fn_tif <- "dem.tif"
# Now run gdal_grid:
r.dem <- setMinMax(gdal_grid(src_datasource=fn_vrt,
dst_filename=fn_tif,a="invdist:power=2.0:smoothing=1.0",
txe=c(85000,89000),tye=c(894000,890000),outsize=c(400,400),
of="GTiff",ot="Float64",l="dem",output_Raster=TRUE,verbose=TRUE))
plot(r.dem)