[mapserver-users] Raster rendering performance and zoom levels

[Ian Walberg]

Frank,

We can test again tomorrow with and without the overviews.

I had assumed as the overviews would be closer to what we needed but not the correct resolution it would reduce the image resizing but not eliminate it.

The 4 images are the NASA Blue Marble 1km imagery split into 4 files.

Thanks

Ian

-----Original Message-----
From: fwarmerdam at gmail.com [mailto:fwarmerdam at gmail.com] On Behalf Of Frank Warmerdam
Sent: Tuesday, December 13, 2011 4:18 PM
To: Ian Walberg
Subject: Re: [mapserver-users] Raster rendering performance and zoom levels

Ian,

Hmm, four images shouldn't be an issue.  If overviews are built and being used rendering should not be noticably slower at different resolutions.  Can you confirm that the overviews exist with gdalinfo?

Best regards,

On Tue, Dec 13, 2011 at 4:11 PM, Ian Walberg <ian.walberg at airborne.aero> wrote:
> Frank,
>
> With the current test setup we have the whole earth as 4 images in a shp file.
>
> As the area displayed increases the images are taking much longer to render, we had put this down to the image data being re-sampled as it was shrunk to fit.
>
> Thanks
>
> Ian
>
> -----Original Message-----
> From: fwarmerdam at gmail.com [mailto:fwarmerdam at gmail.com] On Behalf Of 
> Frank Warmerdam
> Sent: Tuesday, December 13, 2011 4:07 PM
> To: Ian Walberg
> Subject: Re: [mapserver-users] Raster rendering performance and zoom 
> levels
>
> Ian,
>
> I'm surprised you are seeing significant performance problems with one raster image with overviews as you zoom out.  I suspect there is more going on and that understanding what that is might be helpful.  There is just one image, right?
>
> Best regards,
> Frank
>
> On Tue, Dec 13, 2011 at 3:32 PM, Ian Walberg <ian.walberg at airborne.aero> wrote:
>> 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
>>>
>>>
>>>
>>>
>>>
>>>
>>> _______________________________________________
>>> mapserver-users mailing list
>>> mapserver-users at lists.osgeo.org
>>> http://lists.osgeo.org/mailman/listinfo/mapserver-users
>>>
>>
>>
>>
>> --
>> ---------------------------------------+-----------------------------
>> ---------------------------------------+-
>> ---------------------------------------+--
>> ---------------------------------------+------
>> 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
>
>
>
> --
> ---------------------------------------+------------------------------
> ---------------------------------------+--
> ---------------------------------------+------
> 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



-- 
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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