[gdal-dev] Tiling aerial photos

[Duarte Carreira]

For some reason stats in the individual files did not solve the issue, had to put it in the vrt.

Duarte

-----Mensagem original-----
De: Etienne Tourigny [mailto:etourigny.dev at gmail.com] 
Enviada: quinta-feira, 12 de Julho de 2012 13:28
Para: Duarte Carreira
Cc: p.meems at topx-group.nl; gdal-dev at lists.osgeo.org
Assunto: Re: [gdal-dev] Tiling aerial photos

You should generate the stats for every file, as you will probably get incorrect results with your method

for f in *.tif; do gdalinfo -stats $f ; done

On Thu, Jul 12, 2012 at 9:03 AM, Duarte Carreira <DCarreira at edia.pt> wrote:
> Hi Paul.
>
>
>
> I had to build a big vrt. The one trick that got it loading very fast 
> into qgis was adding statistics to each rasterband:
>
>   <Metadata>
>
>       <MDI key="STATISTICS_MAXIMUM">255</MDI>
>
>       <MDI key="STATISTICS_MEAN">111.6784426525</MDI>
>
>       <MDI key="STATISTICS_MINIMUM">0</MDI>
>
>       <MDI key="STATISTICS_STDDEV">52.100074055799</MDI>
>
>     </Metadata>
>
>
>
> I just got stats from a subset and used that for all bands.
>
>
>
> Duarte
>
>
>
> De: Paul Meems (Top-X) [mailto:p.meems at topx-group.nl]
> Enviada: quinta-feira, 12 de Julho de 2012 12:11
> Para: gdal-dev at lists.osgeo.org
> Assunto: Re: [gdal-dev] Tiling aerial photos
>
>
>
> Thanks Dmitry and Even,
>
> The aerial photos are north-up and are in the same projection and I 
> think also in the same resolution.
> It are commercial aerial photos.
>
> The Correlator project sounds very interesting but not necessary in my case.
> I'll try to implement the VRT format and see what the performance will be.
> If it is fast we don't need to tile.
>
> Thanks,
>
> Paul
>
> 2012/7/12 Even Rouault <even.rouault at mines-paris.org>
>
> Selon "Paul Meems (Top-X)" <p.meems at topx-group.nl>:
>
>> Thanks Even,
>>
>> http://www.gdal.org/gdalbuildvrt.html does seems very interesting.
>> As I understand it, it will do the merging part (without actually 
>> merging).
>
> The VRT driver will do on-the-fly merging of tiles that have overlapping.
> The
> VRT itself is just a XML file.
>
>
>>
>> But it doesn't do the tiling part, right?
>
> No, I wasn't sure if your photos were already regularly tiled or not. 
> Note that the VRT accepts non regularly tiled images. They can have 
> overlapping, gaps, different resolutions, etc. The main constraints 
> are :
> - they are in the same projection
> - they are "north-up", that is to say there is no rotation or skewing 
> term in their geotransform matrix
> - they have the same number of bands
>
>
>> Or is the vrt so optimized tiling
>> is no longer necessary?
>
> Not necessary. Note that the VRT has no internal spatial indexing, so 
> if you have several dozains of thousands of images in a VRT, it might 
> slow down because it will iterate over all the image descriptions 
> (without needing to open them however, all the information is in the 
> VRT) to see if they intersect with the request window. But I'd expect 
> the number of images in the VRT to be really high for that effect to 
> become noticeable.
>
>>
>> Thanks,
>>
>> Paul
>
> 2012/7/12 Dmitry Baryshnikov <polimax at mail.ru>
>
> 12.07.2012 14:36, Paul Meems (Top-X) пишет:
>
> Thanks Even,
>
> http://www.gdal.org/gdalbuildvrt.html does seems very interesting.
> As I understand it, it will do the merging part (without actually merging).
>
> But it doesn't do the tiling part, right? Or is the vrt so optimized 
> tiling is no longer necessary?
>
> Thanks,
>
> Paul
>
> 2012/7/12 Even Rouault <even.rouault at mines-paris.org>
>
> Selon "Paul Meems (Top-X)" <p.meems at topx-group.nl>:
>
>
>> Hi list,
>>
>> I have several aerial photos and I use MapWindow GIS to view them.
>> MapWindow is already using GDAL v1.8
>>
>> Instead of loading each aerial photo as an individual layer I want to 
>> create a local tiles store of the photos.
>> I can then just load the tiles I need based on the scale and view. 
>> This will most likely improve the performance.
>>
>> The process will be something like this:
>> 1. Get the filenames of the photos
>> 2. Merge them into one
>> 3. Create tiles
>> 4. Put the tiles in a SQLite database
>>
>> My first question: Is the above suggested process correct or should I 
>> do it differently?
>> My second question: What GDAL functions should I look into to 
>> accomplish my process?
>
> You could try to make a VRT from all your photos. It will be seen as a 
> single GDAL dataset, and will take care of the burden of opening the 
> underlying photos when needed. You can use the gdalbuildvrt utility to 
> create the VRT from the photos.
>
>
>>
>> Thanks,
>>
>> Paul Meems
>> The Netherlands
>>
>
> _______________________________________________
> gdal-dev mailing list
> gdal-dev at lists.osgeo.org
> http://lists.osgeo.org/mailman/listinfo/gdal-dev
>
>
>
> _______________________________________________
>
> gdal-dev mailing list
>
> gdal-dev at lists.osgeo.org
>
> http://lists.osgeo.org/mailman/listinfo/gdal-dev
>
> There is an interesting work connected aerial imagery:
> http://trac.osgeo.org/gdal/wiki/Correlator
> http://correlatorgsoc2012.blogspot.com/
>
> Best regards,
>     Dmitry
>
>
> _______________________________________________
> gdal-dev mailing list
> gdal-dev at lists.osgeo.org
> http://lists.osgeo.org/mailman/listinfo/gdal-dev
>
>
>
>
> _______________________________________________
> gdal-dev mailing list
> gdal-dev at lists.osgeo.org
> http://lists.osgeo.org/mailman/listinfo/gdal-dev