[mapserver-users] Raster rendering performance and zoom levels

[Ian Walberg]

We have added the overviews and they help but as we are able to fix the zoom levels we are hoping to go a step further.

Thanks

Ian

-----Original Message-----
From: fwarmerdam at gmail.com [mailto:fwarmerdam at gmail.com] On Behalf Of Frank Warmerdam
Sent: Tuesday, December 13, 2011 3:29 PM
To: Ian Walberg
Cc: mapserver-users at lists.osgeo.org
Subject: Re: [mapserver-users] Raster rendering performance and zoom levels

Ian,

The normal approach to slow rendering at larger scales is to build pyramids/overviews on large images.  This can generally be accomplished something like:

  gdaladdo big.tif 2 4 8 16 32 64 128

The gdaladdo command should work on virtually all GDAL supported raster formats.  There are also things you could do to produce very specific overviews for the particular rendering resolutions you want to produce.  But I'd suggest first trying the above generic solution and see if it is sufficient for your needs.  Some gdaladdo docs are available
at:

  http://www.gdal.org/gdaladdo.html

Best regards,


On Tue, Dec 13, 2011 at 3:21 PM, Ian Walberg <ian.walberg at airborne.aero> wrote:
>
>
> We have an application which is using php  mapscript to render maps at 
> a number of different zoom levels, these zoom levels can be fixed and 
> the maps are centered on a specific location.
>
>
>
> So we calculate the extent based on the zoom level and the current 
> required center lat/long.
>
>
>
> The raster imagery we are using is approx. the same resolution as the 
> max zoom (smallest extent) and in this case the map rendering is the fastest.
>
>
>
> As we zoom out and the extent increases the map rendering is slower, 
> we are assuming this is because the imagery is being resized which is 
> processor/memory intensive.
>
>
>
> Now the question,  how do we create imagery sets for each zoom level 
> so that they are the required resolution and no re-sizing is required?
>
>
>
> We are using mapserver without a client to generate the images on a server.
>
>
>
> I hope this makes sense.
>
>
>
> Thanks
>
>
>
> Ian
>
>
>
>
>
>
> _______________________________________________
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>



-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com light and sound - activate the windows | http://pobox.com/~warmerdam and watch the world go round - Rush    | Geospatial Software Developer