Splitting/tiling a raster - gdaladdo - [Summary]

[Ed McNierney]

Stefan -

If you really care about performance, get rid of that JPEG.  It's just
about the poorest-performing raster data type for mapping applications.
Converting it to TIFF will help, especially for map views that display a
portion of the image from each file.

	- Ed

Ed McNierney
President and Chief Mapmaker
TopoZone.com / Maps a la carte, Inc.
73 Princeton Street, Suite 305
North Chelmsford, MA  01863
Phone: +1 (978) 251-4242
Fax: +1 (978) 251-1396
ed at topozone.com 

-----Original Message-----
From: UMN MapServer Users List [mailto:MAPSERVER-USERS at LISTS.UMN.EDU] On
Behalf Of Stefan Schwarzer
Sent: Wednesday, July 13, 2005 5:25 AM
To: MAPSERVER-USERS at LISTS.UMN.EDU
Subject: Re: [UMN_MAPSERVER-USERS] Splitting/tiling a raster - gdaladdo
- [Summary]

Well, this was very useful. Just for the records (and other users with
similar questions):

1) I used a 200 MB JPEG image for building the overviews as indicated
below by Bart.

2) gdaladdo -r average xxx.jpg 2 4 8 16

(Small error message here. But still it worked its way through.
ERROR 6: The JPEG driver does not support update access to existing
datasets.
Corrupt JPEG data: 14964 extraneous bytes before marker 0xed
0...10...20...30...40...50...60...70...80...90...100 - done.)

3) An additional file with the extension xxx.jpg.ovr was created.

4) This file name should appear in the map file for that specific layer.

5) The total extent display is really fast. And the zooms are being
generated very quickly too.

6) Nice, really nice. Thanks a lot...



> You can build overviews with gdaladdo:
>
> http://www.gdal.org/gdal_utilities.html#gdaladdo
>
> Eg:
>
> gdaladdo -r average abc.tif 2 4 8 16
>
> Try that first I would say.
>
> Best regards,
> Bart
>
> Bart van den Eijnden
> Syncera IT Solutions
> Postbus 270
> 2600 AG  DELFT
>
> tel.nr.: 015-7512436
> email: BEN at Syncera-ITSolutions.nl
>
>
>>>> Stefan Schwarzer <stefan.schwarzer at GRID.UNEP.CH> 07/12/05 12:02pm 
>>>> >>>
>>>>
>
>
>> Which format is your raster currently in?
>>
>
> TIF or JPEG
>
>
>>
>> If it is performance, building overviews could also help for certain 
>> situations.
>>
>
> So, how can I build overviews then?
>
>
>>
>> At which scales do you display your raster? Also at full extent?
>>
>
>  From full extent (at the beginning - a couple of hundreds km wide) to

> then, when zooming, a couple of km wide.
>
>
>>
>> Best regards,
>> Bart
>>
>> Bart van den Eijnden
>> Syncera IT Solutions
>> Postbus 270
>> 2600 AG  DELFT
>>
>> tel.nr.: 015-7512436
>> email: BEN at Syncera-ITSolutions.nl
>>
>>
>>
>>>>> Stefan Schwarzer <stefan.schwarzer at GRID.UNEP.CH> 07/12/05 11:55am 
>>>>> >>>
>>>>>
>>>>>
>> Thanks Bart for the quick response,
>>
>> aehh, yes, performance. But perhaps there is no need to split it up?
>> Is it that what you mean? Gush, somehow I don't really get it how 
>> this tiling works, stupid me....
>>
>> Stef
>>
>>
>>
>>
>>> Hi Stefan,
>>>
>>> since gdal_translate has the option to select a subwindow (srcwin) 
>>> from your sourcefile, you can use it to split your raster file into 
>>> subimages.
>>>
>>> http://www.gdal.org/gdal_utilities.html#gdal_translate
>>>
>>> After that, you do use gdaltindex to create a tileindex. That part 
>>> is described in the raster howto:
>>>
>>> http://mapserver.gis.umn.edu/doc44/raster-howto.html
>>>
>>> Btw, what is the exact reason you want to split up your raster?
>>> Performance?
>>>
>>> Best regards,
>>> Bart
>>>
>>> Bart van den Eijnden
>>> Syncera IT Solutions
>>> Postbus 270
>>> 2600 AG  DELFT
>>>
>>> tel.nr.: 015-7512436
>>> email: BEN at Syncera-ITSolutions.nl
>>>
>>>
>>>
>>>
>>>>>> Stefan Schwarzer <stefan.schwarzer at GRID.UNEP.CH> 07/12/05 11:39am

>>>>>> >>>
>>>>>>
>>>>>>
>>>>>>
>>> Hi,
>>>
>>> this subject is really not new. But I haven't found any real how-to 
>>> for the whole story. Perhaps somebody could clarify the steps 
>>> needed.
>>> when starting with an image of some larger size and when ending with

>>> a tiled raster. Cause I guess that' what has to be done.
>>> - At least I have now one single big raster. As far as I understood 
>>> I need to split the big image into smaller ones. But how?
>>> - And then I can use gdaltindex to build the shapefile to define the

>>> tiles. Right?
>>>
>>> Thanks for clarification.
>>>
>>>
>>>
>>
>>
>