[Gdal-dev] Flashy colors in a pyramid

acangi aca at ngi.be
Wed Aug 19 08:14:23 EDT 2009

Hi Christian,

Thanks for your reply and thanks for writing gdal_retile. I use it a lot and
it works great. 

I'm not sure I understand you well. On the highest level of the pyramid (the
top) there's only one file. Gdal_retile already created the files needed for
the mosaic (shp, shx, dbf and prj). Would you like me to re-create them ? 

Or do you mean at the base of the pyramid ? 


Christian Müller wrote:
> Hi, Christian speaking, I wrote the gdal_retile.py utility. 
> Could you try to run a gdal_merge.py on the highest pyramid level
> containing 
> this strange area. What is the result.?  I want to know if the problem is 
> gdal_retile.py or geoserver. 
> acangi writes: 
>> Hello list, 
>> I created a pyramid of aerial photos using gdal_retile.py and now see
>> there
>> are strange zones in the pyramid. I'm trying to understand why I got this
>> strange results and how I can fix it (Bombing the area to make sure it
>> looks
>> like what I have ?). Description :
>> 1. The command I used was gdal_retile.py -targetDir pyramid/ -levels 12
>> -pyramidOnly -v -s_srs /path/to/prjs/3812.prj -ps 10000 10000 -r bilinear
>> -co "TILED=YES" -co "COMPRESS=LZW" -co "INTERLEAVE=PIXEL" -tileIndex
>> orthocol -tileIndexField location /path/to/source/files/*.tif &
>> 2. In the source files, I see nothing special. The tiles in this area
>> look
>> like the other ones.
>> 3. On the first (generated) level of the pyramid, I see a small area
>> (alias
>> SMALL_SQUARE : 256m x 256m) in blue :
>> http://n2.nabble.com/file/n3470903/BlueSquare.jpg 
>> 4. On the next levels of the pyramid, a black rectangle 512m x 256m is
>> now
>> visible where SMALL_SQUARE was : 
>> http://n2.nabble.com/file/n3470903/BlackRect.jpg  
>> and the area corresponding to the first level tile containing
>> (alias BIG_SQUARE : 10000m x 10000m) is in green : 
>> http://n2.nabble.com/file/n3470903/GreenSquare.jpg 
>> 5. I view the pyramid in geoserver, the tiles look like they are on disk,
>> except at the first level, geoserver doesn't show me the full
>> only parts of it. In geoserver logs, I find nothing very interesting, it
>> all
>> looks the same whether or not I'm looking at BIG_SQUARE.
>> 6. If I set OutputTransparentColor to #000000 (the background color),
>> BIG_SQUARE is now invisible (in geoserver) 
>> So, my questions are :
>> Why did it happen ? I suppose it's just a random error...
>> How can I fix it ? Is there any way other than rebuilding the whole
>> pyramid
>> ? 
>> Any idea is welcome, 
>> Alain
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