[mapserver-users] It takes more than 2 minutes for my map server to generate a world map

[Rahkonen Jukka]

Hi,

It is really essential to avoid opening all the 4659 files.  Redused resolution overview images and layer group is the way to go so that there are never more than, let's say, 20-30 images to open for one call.  And gdaladdo does help further.  And the third step is to have internally tiled image files.  When zoomed in so that just a minory part of the image file is needed for generating the output tiling helps in getting the desired part of an image fast.

Mapserver itself can be used for creating overview images, just define a geotiff outputformat (http://mapserver.org/mapfile/outputformat.html) and make some requests with well controlled BBOXes.  

-Jukka Rahkonen-

Stephen Woodbridge wrote:

> You probably need to run gdaladdo to add reduced resolution overviews of
> you images which will speed up display when you are zoomed way out.

> for x in *.tif ; do
>    gdaladdo $x 2 4 8 16 32 64 128 256
> done

> Regardless, to draw the whole world you will need to open all 4659 files
> and fetch something from each one. You can probably speed this up be
> creating a super overlay image at reduced resolution and setup you
> mapfile to use the super overlay when zoomed out and then change to the
> tiles when zoomed in.

> Read this might help:
> http://mapserver.org/optimization/raster.html

> Also the GDAL list will be able to help you on how to create a super
> overlay at reduced resolution.

-Steve W

On 7/28/2011 11:17 AM, Carlos Ruiz wrote:
> JK (?),
>
> One question: did you use gdaltindex ?
>
> IC Carlos Ruiz
>
> *From:* jk <jk.chen at sdl.usu.edu>
> *To:* mapserver-users at lists.osgeo.org
> *Sent:* Wednesday, July 27, 2011 6:20 PM
> *Subject:* [mapserver-users] It takes more than 2 minutes for my map
> server to generate a world map
>
> Hi,
>
> I have a tile system of 4659 tiles, each is a 5 meter resolution raster
> image a particular spot in the world (as you know it is sparse, the
> collection of tiles do not cover the enter world).
>
> When I asking for a map of the world (ie, high-level view, a bbox with
> values close to the lonlat boundary of the world), my map server
> consistently takes long time to finish, (close to 2.5 minutes, yeah,
> minutes, not seconds). This is very slow.
>
> If I submit a bbox that matches a particular tile, the map is returned
> instantly.
>
> How could it take so long to generate the world map?
>
> How to fix that?
>
> Anything I'm missing? Any idea?
>
> I'm not using tile cache yet. But I think 2.5 minutes for world view is way
> too slow. Something must be wrong.
>
> If you know of any clues, let me know.
>
> Thanks for your help.
>
> JK
>
>
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