[gdal-dev] GXF -- Grid eXchange File to AAIGrid -- Arc/Info ASCII Grid No Value Issue

Even Rouault even.rouault at mines-paris.org
Mon Jun 14 17:23:27 EDT 2010


David,

the issue was in the GXF driver that returns the nodata value as a double 
precision real, but the pixel data as single precision real. So when 
translating to AAIGrid, you can see the difference in precisions.

In trunk (r19868), I've made 2 changes :
* cast nodata value to float to be consistant with precision of pixel data
* add a GXF_DATATYPE configuration option that can be set to Float64 to get 
full precision for nodata value and pixel values.

Best regards,

Even

Le Monday 14 June 2010 21:16:41 David Baker (Geoscience), vous avez écrit :
> All,
>
> Using OpenEV from FWTools version 2.4.7 to convert the GXF file found at
> http://pubs.usgs.gov/of/2000/ofr-00-0042/data/ from the GXF format to
> AAIGrid format I have found an issue.  In the GXF file the #DUMMY
> value/string is -1e32 and this is the same value/string found in the data
> portion of the GXF file.  After conversion in the AAIGrid file, the NODATA
> line reads
>
> NODATA_value -1.0000000000000001e+032
>
> but the value -1.0000000331813535e+032 is found in the data portion of the
> AAIGrid file where the value -1.0000000000000001e+032 should be found.  As
> OpenEV uses GDAL/OGR to do the conversion I have posted this issue here.
>
> Thanks,
>
> David M. Baker
> Senior Geologist - Chief Technology Advisor
> Chesapeake Energy Corporation
> 405-935-3715 office
> 405-496-5373 cell
> david.m.baker at chk.com<mailto:david.m.baker at chk.com>
>
>
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