[mapserver-users] How to tile a large TIF image?

[Paul Spencer]

Stefan,

I don't think you can specify 10'', you need something in pixels.  But  
the command is also probably not what you really need to do.

More likely, you should be doing the following:

gdal_translate -co "TILED=YES" gebco/bathymetry.tif gebco/ 
bathmetry_tiled.tif

This will create a single tif file that has an internal block size of  
256x256 - you can think of this as having broken your tif up into  
256x256 tiles but keeps them all within the same file.  This is  
equivalent to breaking the tif up into individual files, creating a  
shapefile that has rectangles for each individual files' extent, and  
using that as a tile index in mapserver.

Next, you want to do this:

gdaladdo gebco/bathymetry.tif 2 4 6 8 16

this will pre-compute smaller versions of the tif image called  
overviews at 1/2, 1/4 1/6 1/8 and 1/16 of the original size of the tif  
- this makes it much more efficient for gdal to return exactly what  
mapserver is asking for at any given scale.  Depending on the range of  
scales that you need to display your raster image at, you can add more  
overview levels (or take some away).

With this two commands, you can make your rasters much more efficient  
for mapserver and probably avoid the need to split them up into many  
files.

It does make the file somewhat larger.  If you are working with very  
large files ( > 4GB ) then you may run into some problems with tiff  
and may need to investigate another format or a compressed format like  
ECW or MrSID (both requiring commercial licenses I believe).

There are also some built in compression schemes for tiffs in gdal  
which you can apply when running gdal_translate (see http://www.gdal.org/frmt_gtiff.html 
  for creation options), for instance:

gdal_translate -co "TILED=YES" -co "COMPRESS=JPEG" -co  
"JPEG_QUALITY=80" gebco/bathymetry.tif gebco/bathmetry_tiled.tif

would compress the tif using JPEG compression (lossy) set to 80% (low  
compression, small loss).

Cheers

Paul



On 18-Apr-08, at 5:47 AM, Stefan Schwarzer wrote:
> Thanks for the info.
>
> Did it like this:
>
> Library/Frameworks/GDAL.framework/Versions/1.5/Programs/ 
> gdal_translate -outsize 10'' 10'' -co TILED=YES gebco/bathymetry.tif  
> gebco/bathymetry_tiled.tif
>
> But get the message: "Segmentation fault"
>
> Anything that I did wrong? Or should do differently?
>
> Thanks for a hint,
>
> Stef
>
>> Hi,
>>
>> Gdal_translate program has options for you:
>>
>> c:\FWTools>gdal_translate
>> Usage: gdal_translate [--help-general]
>>        [-ot {Byte/Int16/UInt16/UInt32/Int32/Float32/Float64/
>>              CInt16/CInt32/CFloat32/CFloat64}] [-strict]
>>        [-of format] [-b band] [-outsize xsize[%] ysize[%]]
>>        [-scale [src_min src_max [dst_min dst_max]]]
>>        [-srcwin xoff yoff xsize ysize] [-projwin ulx uly lrx lry]
>>        [-a_srs srs_def] [-a_ullr ulx uly lrx lry] [-a_nodata value]
>>        [-gcp pixel line easting northing [elevation]]*
>>        [-mo "META-TAG=VALUE"]* [-quiet] [-sds]
>>        [-co "NAME=VALUE"]*
>>        src_dataset dst_dataset
>>
>> By playing with -srcwin or possibly with -outsize and -projwin you  
>> should be able to split your image as you wish.  Read more from
>> http://gdal.org/gdal_translate.html
>>
>> -Jukka Rahkonen-
>>
>>
>>
>> Lähettäjä: mapserver-users-bounces at lists.osgeo.org [mailto:mapserver-users-bounces at lists.osgeo.org 
>> ] Puolesta Stefan Schwarzer
>> Lähetetty: 18. huhtikuuta 2008 12:05
>> Vastaanottaja: mapserver-users at lists.osgeo.org
>> Aihe: [mapserver-users] How to tile a large TIF image?
>>
>> Hi there,
>>
>> I would like to use instead of single large tif image smaller  
>> tiles. Although I am well aware of mapserver's and gdal's  
>> possibilities to create the shapes for it, I first need to "split"  
>> the large tif into 20 or 50 or 100 tiles.
>>
>> Can anyone give me a hint with what kind of software this is  
>> possible?
>>
>> There is an ArcGIS script, but it doesn't work on my machine ( http://arcscripts.esri.com/details.asp?dbid=13978 
>>  ).
>>
>> Thanks for any hints,
>>
>> Stef
>>
>>  ____________________________________________________________________
>>
>>   Stefan Schwarzer
>>
>>   Lean Back and Relax - Enjoy some Nature Photography
>>   http://photoblog.la-famille-schwarzer.de
>>
>>   Appetite for Global Data? UNEP GEO Data Portal:
>>   http://geodata.grid.unep.ch
>>    
>> ____________________________________________________________________
>>
>>
>>
>>
>>
>>
>
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__________________________________________

    Paul Spencer
    Chief Technology Officer
    DM Solutions Group Inc
    http://www.dmsolutions.ca/