[R-sig-Geo] get rgdal to read ENVI raster?

[Felix Andrews]

Thanks Michael

The extension is "flt" (float type). This resulted in a sensible image:

foo <- readBin("G:/Projects/Tuross/surface_files/rainfall_surface/year2000/rainGrid_20001.flt",
"double", n=200*200, size=4, endian="little")
foo[foo==-9999] <- NA
range(foo, finite=T)
# 18.83187 80.23850
image(matrix(foo, ncol=200))
# sensible image, but flipped vertically I think

This is what GDAL does:

grid1 <- readGDAL("G:/Projects/Tuross/surface_files/rainfall_surface/year2000/rainGrid_20001.flt")
# G:/Projects/Tuross/surface_files/rainfall_surface/year2000/rainGrid_20001.flt
has GDAL driver EHdr
# and has 200 rows and 200 columns
# Closing GDAL dataset handle 0x02248358...  destroyed ... done.
str(grid1 at data[[1]])
# int [1:40000] 118 215 97 66 180 213 96 66 23 133 ...

So the problem is that it thinks it is an integer type, whereas in
fact it is a 4-byte float type.

As a temporary hack, maybe I can use GDAL to import it, then just
replace the @data slot with the correct numeric data.

Felix

On 8/8/07, Michael Sumner <mdsumner at utas.edu.au> wrote:
> Hi Felix, can you provide the file? The Ehdr driver is probably right, but
> you might have some trouble with the values being interpreted.
>
> I'd like to see more information about the "just noise" data.
>
>
> Cheers, Mike.
>
> -----Original Message-----
> From: r-sig-geo-bounces at stat.math.ethz.ch
> [mailto:r-sig-geo-bounces at stat.math.ethz.ch] On Behalf Of Felix Andrews
> Sent: Wednesday, 8 August 2007 2:10 PM
> To: r-sig-geo at stat.math.ethz.ch
> Subject: Re: [R-sig-Geo] get rgdal to read ENVI raster?
>
> Sorry, I just realised that it is not an ENVI raster after all.
> Looks like it is a "ESRI binary raster format" described at
> http://coastwatch.noaa.gov/cw_form_br.html
> and there does not seem to be a GDAL driver for it.
>
>
> On 8/8/07, Felix Andrews <felix at nfrac.org> wrote:
> > Hi,
> >
> > I am trying to use rgdal to read in an "ENVI .hdr labelled raster"
> > --see http://www.gdal.org/frmt_various.html#ENVI
> > but GDAL uses the wrong driver, "ESRI .hdr labelled"
> > --see http://www.gdal.org/frmt_various.html#EHdr
> >
> > So the imported grid data is just noise.
> > I can not figure out how to make GDAL/rgdal use the ENVI driver.
> > Suggestions would be appreciated.
> >
> > The .hdr file contains:
> > NCOLS      200
> > NROWS      200
> > XLLCORNER    148.50000000000
> > YLLCORNER   -37.002500000000
> > CELLSIZE    0.10000000000000E-01
> > NODATA_VALUE   -9999.000
> > BYTEORDER LSBFIRST
> >
> >
> > > sessionInfo()
> > R version 2.5.1 (2007-06-27)
> > i386-pc-mingw32
> >
> > locale:
> > LC_COLLATE=English_Australia.1252;LC_CTYPE=English_Australia.1252;LC_M
> > ONETARY=English_Australia.1252;LC_NUMERIC=C;LC_TIME=English_Australia.
> > 1252
> >
> > attached base packages:
> > [1] "stats"     "graphics"  "grDevices" "utils"     "datasets"
> > "methods"   "base"
> >
> > other attached packages:
> >          rgdal       RArcInfo       maptools        foreign
> >  sp    hydrosanity
> >       "0.5-14"        "0.4-7"       "0.6-14"       "0.8-20"
> > "0.9-14"       "0.8.57"
> > plotAndPlayGTK    cairoDevice          RGtk2        lattice
> >       "0.8.55"          "2.3"      "2.10.13"       "0.16-2"
> >
> >
> > --
> > Felix Andrews / 安福立
> > PhD candidate
> > Integrated Catchment Assessment and Management Centre The Fenner
> > School of Environment and Society The Australian National University
> > (Building 48A), ACT 0200 Beijing Bag, Locked Bag 40, Kingston ACT 2604
> > http://www.neurofractal.org/felix/
> > voice:+86_1051404394 (in China)
> > mobile:+86_13522529265 (in China)
> > mobile:+61_410400963 (in Australia)
> > xmpp:foolish.android at gmail.com
> > 3358 543D AAC6 22C2 D336  80D9 360B 72DD 3E4C F5D8
> >
>
>
> --
> Felix Andrews / 安福立
> PhD candidate
> Integrated Catchment Assessment and Management Centre The Fenner School of
> Environment and Society The Australian National University (Building 48A),
> ACT 0200 Beijing Bag, Locked Bag 40, Kingston ACT 2604
> http://www.neurofractal.org/felix/
> voice:+86_1051404394 (in China)
> mobile:+86_13522529265 (in China)
> mobile:+61_410400963 (in Australia)
> xmpp:foolish.android at gmail.com
> 3358 543D AAC6 22C2 D336  80D9 360B 72DD 3E4C F5D8
>
> _______________________________________________
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>
>


--
Felix Andrews / 安福立
PhD candidate
Integrated Catchment Assessment and Management Centre
The Fenner School of Environment and Society
The Australian National University (Building 48A), ACT 0200
Beijing Bag, Locked Bag 40, Kingston ACT 2604
http://www.neurofractal.org/felix/
voice:+86_1051404394 (in China)
mobile:+86_13522529265 (in China)
mobile:+61_410400963 (in Australia)
xmpp:foolish.android at gmail.com
3358 543D AAC6 22C2 D336  80D9 360B 72DD 3E4C F5D8