[GRASS-user] howto make my srtm-dem jump the GIS gap

[paallen at attglobal.net]

Rudy,

This is a very strange problem.  I export rasters
out of Grass and into ArcGIS all the time.

When I export them out as an Arc ASCII format I
never change the window-line-feed.  The ArcInfo
ASCII format always imports directly into ArcGIS
with the Toolbox "Conversion Tools>To Raster>ASCII
to Raster".  The only downside of
exporting/importing by way of ASCII is that it is
very slow.  I have used this method for SRTM for
all of Colombia and Peru (~1.1GB in binary float
form each).

If you export the rasters out as binary using
r.out.bin you must modify the grass generated
header file.  The text header file must look like
this:
NCOLS xxx
NROWS xxx
XLLCENTER xxx | XLLCORNER xxx
YLLCENTER xxx | YLLCORNER xxx
CELLSIZE xxx
NODATA_VALUE xxx
BYTEORDER <MSBFIRST | LSBFIRST>

typically grass puts "some" of this information
into the world file.  Just give the binary file
the extension .flt and the text header file *.hdr.
 And remember the binary file must be an IEEE
Floating-point format,32-bit signed.  This method
is faster but you unfortunaly have to manually
edit the header file and erase the header file. 
It appears the ArcGIS does not use the header
files always.

Years ago I also exported Grass raster out as
binary and the hand generated an ER-Mapper text
header file and opened them into ArcGIS directly
using ERMapper plugin for ERS/ECW/ALG files.  But
at the moment I don't have my old scripts for that
or a copy of ER-Mapper figure out how I did it.

Good luck and have patients.  Importing/Exporting
rasters is a horrible nightmare.

Phillip J. Allen
Consulting Geochemist


Hey all!

> > r.out.gdal in=dem out=dem.tif
cre="COMPRESS=PACKBITS" type=Int16

This works.

I still wonder why I can't produce a working
Arc-Grid file...?

> > r.out.gdal in=clean_alle out=clean_test_arc
type=Byte format=AAIGrid

does not work with ArcGIS 9.1: Cannot open file,
Catalog can not show any data.
I tried again to safe the ascii-File in
Windows-Linefeed-Mode, again
without success.
But I did not try that with the complementary
prj, will do then. (has
only one line...)

I experimented with
r.out.gdal in=clean_alle out=clean_Float32.asc
type=Float32 format=AAIGrid
though the ArcGIS-Test is yet to come.
QGIS fails on this file. The Properties-Window
tells me a zero Pixel-size !?
The Minimum, Maximum-Values are correct.

Any more tips for me?
Is r.out.arc obsolet now since gdal is there?

All the best
Rudy

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