Thanks Even,
I started with the implementation of GDAL in MapWinGIS, but I also tried
it with my stand-alone installation of GDAL
I'm using the precompiled windows-version, 32bit from 18 jan 2015 bit by
Tamas: release-1800-gdal-1-11-1-mapserver-6-4-1
<http://www.gisinternals.com/query.html?content=filelist&file=release-1800-gdal-1-11-1-mapserver-6-4-1.zip>
However still I get an ascii grid with xxxE9 in nodata-cells.
If I look in my GDAL\bin directory I see a gdal111.dll there, so it must
be the correct version I'm using.
for the record: this is my batchfile's contents:
setx PATH "C:\GDAL\bin"
"c:\GDAL\bin\gdal\apps\gdal_translate.exe" -of AAIGrid -b 13
C:\Temp\H11_V7_NED_SINGLE_LEVEL_2011013018_000_GB c:\temp\tempgrid.asc
So version is ok, path is ok.
Is it possible that all DLL's have been updated in this package, but
that the stand-alone tools are outdated?
Thanks,
Siebe
-------- Forwarded Message --------
Subject: Re: [gdal-dev] gdal_translate truncates nodata_value <
-4.21358e-09
Date: Fri, 10 Apr 2015 18:28:04 +0200
From: Even Rouault <[email protected]>
To: [email protected]
CC: Siebe Bosch <[email protected]>
Le vendredi 10 avril 2015 17:18:04, Siebe Bosch a écrit :
Dear list,
I am trying to convert one band from a GRIB2-file into an ASCII raster,
using gdal_translate.
Upon inspection (opening the original raster using the MapWinGis
ActiveX-component) and requesting the nodata_value, I get this:
? mygrid.Header.NodataValue
-3.40282346638529E+38 {Double}
Double: -3.40282346638529E+38 {Double}
So far, so good. Now l tried to convert to ASCII using gdal_translate,
with the arguments "-of AAIGrid -b 13" (to ASC, band #13)
Much to my surprise the nodata-value (inside the grid) has changed in
-4.2135788191899337e-009. A NODATA_value in the header has not been set
at all!
Are you using GDAL 1.11 or above ? It should output values with "%.20g"
formatting by default. See end of http://trac.osgeo.org/gdal/ticket/3732
So I tried converting to an ERDAS IMG file. Arguments: "-of HFA -b 13"
Inspecting the results in QGIS I see in the metadata that the
"nodata-value has not been set". The grid itself however contains data
of the Float type, and the cells that should have nodata-values have now
values of -4.21358e-09
My conclusion:
GDAL_Translate does not support numbers smaller than -4.21358e-09. Am I
right?
The problem however is that I do need the nodata-cells to be recognized
correctly. Is there any tool that can help me to correct this? E.g. can
I change the nodata-value of the original (multi-band) grid on forehand?
Or are there additional arguments for gdal_translate that allow values
up to the original nodata_value?
Many thanks,
Siebe
--
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http://www.spatialys.com
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