[Geotiff] GeoTIFFs in ArcGIS 10

[Max Martinez]

April,

 

There are at least two possibilities.

 

First, the mask could be a whole other image in the TIFF file. This
image would have a NewSubfileType tag value with the second bit turned
on. You could disable this bit (then the mask image would either be
ignored or treated as another image in the dataset) or you could remove
the whole mask image by relinking the IFD chain without including the
mask IFD.

 

The other possibility is that the mask is an additional sample included
with the 4 band image (so the image has actually 5 samples). In this
case the ExtraSamples tag would likely have a value of 2 for
"Unassociated alpha data" for the sample representing the mask. If you
changed this value to 0, the mask would possibly be treated as another
band and you might then be able to avoid displaying it.

 

See the TIFF spec
<http://partners.adobe.com/public/developer/en/tiff/TIFF6.pdf>  for more
info. You may also want to investigate the source of the images (why is
that mask being put in there in the first place?).

 

Max

 

From: geotiff-bounces at lists.maptools.org
[mailto:geotiff-bounces at lists.maptools.org] On Behalf Of April Davis
Sent: Thursday, April 07, 2011 2:20 PM
To: geotiff at lists.maptools.org
Subject: [Geotiff] GeoTIFFs in ArcGIS 10

 

All,

 

We have recently upgraded to Esri ArcGIS 10, and have started pulling in
4 band (red,green,blue,IR) GeoTIFFs.  We began to see areas of "no
data".  When looking at the image in other software platforms, we do not
see the areas of "no data".  All the pixels have a value.  We sent an
image to Esri technical support and they replied by stating "The tiff
has a mask tag that ArcGIS didn't use in the past.  At ArcGIS 10.0 we
read and apply this tag.  In this case, the tag specifies band 4 to be a
nodata mask - any place where band 4 has the value 0 will show as
nodata.  This is a setting on the tiff file and not in ArcGIS.  ArcGIS
just started to honor this tag."

 

Does anyone know what tag Esri may be referring to?  If I could figure
out what the tag is or what exactly it specified, then I could remove
the tag or change it.  But I am at a loss as to what to look for.

 

Any help would be appreciated.

 

April H. Davis, GISP

GIS Analyst III

Southwest Florida Water Management District

Mapping and GIS Section

2379 Broad Street

Brooksville, FL 34604

(v): 352-796-7211 x 4216

(f): 352-540-6018

www.watermatters.org

 

IMPORTANT NOTICE:  All E-mail sent to or from this address are public
record and archived.  The Southwest Florida Water Management District
does not allow use of District equipment and E-mail facilities for
non-District business purposes.
 
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