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Dear list,<br>
<br>
I am trying to convert one band from a GRIB2-file into an ASCII
raster, using gdal_translate.<br>
Upon inspection (opening the original raster using the MapWinGis
ActiveX-component) and requesting the nodata_value, I get this:<br>
<br>
? mygrid.Header.NodataValue<br>
-3.40282346638529E+38 {Double}<br>
Double: -3.40282346638529E+38 {Double}<br>
<br>
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)<br>
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!<br>
<br>
So I tried converting to an ERDAS IMG file. Arguments: "-of HFA -b
13"<br>
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<br>
<br>
My conclusion:<br>
<br>
GDAL_Translate does not support numbers smaller than -4.21358e-09.
Am I right? <br>
<br>
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?<br>
<br>
Many thanks,<br>
Siebe<br>
<br>
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<br>
<div class="moz-signature">-- <br>
<img src="cid:part1.03010203.09050105@hydroconsult.nl" border="0"></div>
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