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

[Jerl Simpson]

Just out of curiosity, have you tried using QGIS?
It might solve the issue for you...or might just be a goose chase.

Jerl Simpson
V.P. Systems Engineering
Weather Trends Internationalhttp://www.weathertrends360.com/

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On Thu, Apr 7, 2016 at 7:45 AM, Jason Greenlaw - NOAA Affiliate <
jason.greenlaw at noaa.gov> wrote:

> 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
>>>>
>>>
>>>
>>> _______________________________________________
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>>> gdal-dev at lists.osgeo.org
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>>>
>>
>>
>
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