[gdal-dev] Negative NoData Value with Signed Byte Raster

[Jason Greenlaw - NOAA Affiliate]

Trent,

I am able to load the VRT in ArcMap, and while it does now recognize -128
as the NoData value, it is identifying the raster as unsigned byte despite
the <Metadata> section workaround given by Even, and thus does not properly
respect the NoData areas.  This is strange since it recognizes the original
GeoTIFF as signed byte.  I'm using ArcGIS 10.2.2, which may have something
to do with it.  Perhaps it's fixed with 10.3/10.4.

I have used their Raster Functions before but have not played around with
the Image Analysis window - another reason to upgrade to 10.3+.

Thanks for the tip,
Jason


On Wed, Apr 6, 2016 at 3:58 PM, Hare, Trent <thare at usgs.gov> wrote:

> Jason,
>    VRTs work in ArcMap too - if that helps...? Also have you tried the
> powerful Image Analysis window. It is fairly flexible with output types
> (e.g. float, 8bit) for output at each functional step.
> http://desktop.arcgis.com/en/arcmap/10.3/manage-data/raster-and-images/rasters-with-functions.htm
>
> more:
> http://desktop.arcgis.com/en/arcmap/10.3/manage-data/raster-and-images/what-is-the-image-analysis-window.htm
>
> good luck,
> Trent
>
> On Wed, Apr 6, 2016 at 12:26 PM, Jason Greenlaw - NOAA Affiliate <
> jason.greenlaw at noaa.gov> wrote:
>
>> Thanks for the workaround and quick fix.  The VRT addresses the issue on
>> the data end.  Now it's only an ArcGIS problem :)
>>
>> Jason
>>
>>
>> On Wed, Apr 6, 2016 at 3:10 PM, Even Rouault <even.rouault at spatialys.com>
>> wrote:
>>
>>> Le mercredi 06 avril 2016 20:38:36, Jason Greenlaw - NOAA Affiliate a
>>> écrit :
>>> > Hello,
>>> >
>>> > I've run into a snag trying to assign a negative NoData value to a
>>> Signed
>>> > Byte raster.
>>>
>>> Jason,
>>>
>>> I've just pushed a fix for that in trunk (signed byte is a bit of a
>>> second
>>> class citizen as a data type in GDAL, hence the issues) to avoid the
>>> erroneous
>>> clamping. You're supposed to put negative values.
>>> You can workaround the issue by first creating a VRT by adding
>>>
>>>     <NoDataValue>-128</NoDataValue>
>>>     <Metadata>
>>>       <MDI key="PIXELTYPE">SIGNEDBYTE</MDI>
>>>     </Metadata>
>>>
>>> in <VRTRasterBand>
>>>
>>> and then gdal_translate the VRT as TIFF
>>>
>>> Even
>>>
>>>
>>> --
>>> Spatialys - Geospatial professional services
>>> http://www.spatialys.com
>>>
>>
>>
>> _______________________________________________
>> gdal-dev mailing list
>> gdal-dev at lists.osgeo.org
>> http://lists.osgeo.org/mailman/listinfo/gdal-dev
>>
>
>
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