Jason, In my case I have no problems with no data values... ArcGIS sees them right.
I don't know whether this is important or not... 1) When i convert raster to ascii using ArcGIS it writes no data value as -9999. 2) When i convert the same raster to ascii using gdal_translate, my no data value becomes 255. But in both cases ArcGIS recognizes the no data values... The problem so far that I have seen is this (which i cannot solve yet...): 1) when i use gdal_translate to convert ascii to gtiff file... i don't get statistics computed. even after doing gdalinfo -stats a.tif, i still don't get statistics file .aux.xml 2) but when i open the a.tif file using ArcGIS then ask it to compute the statistics, it computes and generates extra files such as: a.aux and a.tif.vat... Thanks a lot! Riki -----Original Message----- From: "Jason Roberts" <jason.robe...@duke.edu> To: "'Frank Warmerdam'" <warmer...@pobox.com>, "'Riki Tiki'" <mongoose_r...@mail.ru> Date: Thu, 17 Sep 2009 14:24:55 -0400 Subject: RE: [gdal-dev] Re: > Riki, > > Please let us know whether Frank's suggestion works or not. I have been > experimenting with writing GeoTIFFs using GDAL 1.6.0 and the Python bindings > and have not been successful so far at using GDAL to calculate statistics > that ArcGIS recognizes. It would be interesting to know whether this > suggestion will work. > > If anyone is interested, after creating a GTiff with one band, writing > values to the band, flushing the cache, I have been calling > > band.SetStatistics(*band.GetStatistics(False, True)) > > and then looking at the resulting file from ArcGIS 9.3.1 (the latest > version). ArcGIS reports that there are no statistics. I can then calculate > them with ArcGIS, if desired, but like Riki, it would be useful if I did not > need to do this. > > The technique works for .img files (HFA driver). If I do not call > SetStatistics, ArcGIS reports there are no statistics. But when I do call > it, as shown above, ArcGIS can see the statistics. This led me to believe it > was the right technique but that there is a GDAL/ArcGIS incompatibility > around statistics in GeoTIFFs. > > Another thing that ArcGIS users should be aware of is the that the Calculate > Statistics tool in ArcGIS also creates a raster attribute table. GDAL > SetStatistics does not do this. GDAL 1.6.x appears to have some > functionality relating to raster attribute tables but I have not > experimented with it yet. It is another thing to check for if you're looking > for 100% compatibility between GDAL and ArcGIS. > > Finally, I am encountering an issue with NoData values. Riki can you please > let us know if NoData cells show up properly in ArcGIS? When I call > band.SetNoDataValue when creating a GTiff with the Python API, ArcGIS does > not seem to recognize it. I also tried CreateMaskBand() with > GDAL_TIFF_INTERNAL_MASK set to YES. It did not work either. > > Best regards, > > Jason > > -----Original Message----- > From: gdal-dev-boun...@lists.osgeo.org > [mailto:gdal-dev-boun...@lists.osgeo.org] On Behalf Of Frank Warmerdam > Sent: Thursday, September 17, 2009 2:05 PM > To: Riki Tiki > Cc: gdal-dev@lists.osgeo.org > Subject: [gdal-dev] Re: > > Riki Tiki wrote: > > @Frank and Hermann: Thanks a lot! > > > > My other question is as follows: > > > > 1) gdal_translate -of AAIGrid a.tif a.asc > > > > it creates the following: a.asc (ASC File), a.asc.aux (XML Document), and > a > > (IDL project file)... > > Riki, > > Not that the .prj file is not an IDL project file, it is an ArcGIS > projection file. > > > now to do the reverse i do the following: > > > > 2) gdal_translate -of GTiff a.asc a.tif > > > > it creates: a.tif (TIF Image) > > > > but when i open a.tif with ArcGIS it shows that its statistics are not > > calculated... > > > > Can you tell me how to create the 2) with statistics already computed? So > > that when i open it in ArcGis for example I do not have to ask ArcGIS to > > compute the statistics? Thanks a lot! > > If you use a recent enough version of ArcGIS the following *might* > precompute the stats in a useful fashion for ArcGIS. > > gdalinfo -stats a.tif > > Best regards, > > -- > ---------------------------------------+------------------------------------ > -- > I set the clouds in motion - turn up | Frank Warmerdam, > warmer...@pobox.com > light and sound - activate the windows | http://pobox.com/~warmerdam > and watch the world go round - Rush | Geospatial Programmer for Rent > > _______________________________________________ > gdal-dev mailing list > gdal-dev@lists.osgeo.org > http://lists.osgeo.org/mailman/listinfo/gdal-dev > _______________________________________________ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev
