[Gdal-dev] geotiff nodata tag

[Peng Gao]

What's the nodata tag number? 

> -----Original Message-----
> From: Ethan Alpert [mailto:ealpert at digitalglobe.com] 
> Sent: Friday, October 07, 2005 12:42 PM
> To: gdal-dev at lists.maptools.org
> Subject: RE: [Gdal-dev] geotiff nodata tag
> 
> 
> 
> 
> If anyone figures out how to get ArcMap to recognize it 
> automatically please post. I always have to select properties 
> for the image layer and under the Symbology tab select 
> Display Background value (R,G,B) as no color.
> 
> -e
> -----Original Message-----
> From: gdal-dev-bounces at lists.maptools.org
> [mailto:gdal-dev-bounces at lists.maptools.org] On Behalf Of 
> Frank Warmerdam
> Sent: Friday, October 07, 2005 1:17 PM
> To: Matt Wilkie
> Cc: gdal-dev at lists.maptools.org
> Subject: Re: [Gdal-dev] geotiff nodata tag
> 
> 
> On 10/7/05, Matt Wilkie <matt.wilkie at gov.yk.ca> wrote:
> > Hi Folks,
> >
> > Frustratingly ESRI's ArcMap & Catalog  ignore the nodata value in 
> > geotiffs created by gdal (for 8bit greyscale at least, I don't know 
> > about RGBa). Is the nodata tag a specific gdal thing or is 
> it part of 
> > the official GeoTIFF spec?
> 
> Matt,
> 
> It is specifically a GDAL extension to the GeoTIFF format.  I 
> think the only way ArcMap would recognise the nodata value 
> would be if an appopriately constructed Imagine .aux file was 
> associated with it.
> 
> Best regards,
> --
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