[gdal-dev] What options for display of high-quality ortho's via WMS?

[Roger André]

I only have the app running on an internal server at the moment.  I will try
to make a few WMS requests to generate images and will post the resulting
output on an external box for you.  My GSD is 18", but I am probably going
to increase that to 36" for the final product.

Thanks.
--

On Fri, May 2, 2008 at 2:05 PM, Martin Chapman <mchapman at texelinc.com>
wrote:

>  Can you let me download the image you are having issues with?  You want
> to have a pyramid of files that are varying levels.  Ideally they should be
> a factor of 2, i.e… 2, 4, 8, 16, 32 , 64, 128, 256, 512, 1024, 2048, 4096, …
> .  What is the gsd of your base image?
>
>
>
> Martin
>
>
>
> *From:* Roger André [mailto:randre at gmail.com]
> *Sent:* Friday, May 02, 2008 2:54 PM
> *To:* mchapman at texelinc.com
> *Cc:* gdal-dev-bounces at lists.osgeo.org; gdal-dev at lists.osgeo.org
> *Subject:* Re: [gdal-dev] What options for display of high-quality ortho's
> via WMS?
>
>
>
> Well, generating overviews of the 8-bit data produced pretty awful looking
> results.  gdaladdo did warn me, so I can't blame it.  ;)  Also changing the
> resampling to bilinear did not improve the matter.
>
> Is it better to create large, single-image overviews, or to create many
> tiles of varying resolution levels?
> --
>
>
>  On Thu, May 1, 2008 at 11:37 PM, <mchapman at texelinc.com> wrote:
>
> Maybe try generating an overview
> (.ovr) file for the image. Perhaps the resampling will be better. Also see
> if you can specify in mapserver the resampling method to cubic convolution
> or something other than nearest neighbor.
>
> Martin
>
>
> Sent via BlackBerry by AT&T
>
>
> -----Original Message-----
> From: "Roger André" <randre at gmail.com>
>
> Date: Thu, 1 May 2008 21:20:04
> To:gdal-dev at lists.osgeo.org <To%3Agdal-dev at lists.osgeo.org>
> Subject: [gdal-dev] What options for display of high-quality ortho's via
> WMS?
>
>
> Throwing out a general question to this list because I know that many of
> us use a variety of different applications to "get the job done", but use
> the GDAL tools as the common unifier (at least I like to think so).  I'm
> putting together a Mapserver-driven web map that uses OpenLayers to get data
> via WMS.  It's all working quite nicely, except for my aerial photo layer,
> which I am not incredibly pleased with.  Despite using every tweak I could
> find (convert from RGB to 8-bit with pct2rgb.py, use OUTPUTFORMAT with
> GD/PNG, and use "DITHER=YES" in mapfile, I cannot get a very high quality
> rendition of the photo layer in my WMS output.  It looks grainy in areas
> with solid color and generally a bit "pixelly".  So I have a couple of
> questions.
>
> 1.  Is some loss of image quality an unavoidable side-effect of using
> Mapserver?
>
> 2. If not 1, then are there other tweaks that can be done to further
> improve the quality of my output?  (Note that I intend to use Tilecache, so
> maybe slow initial performance may is an acceptable trade off, I dunno.)
>
> 3. If yes to 1, then what other open source tools do a better job of
> rendering photo data?  (I intend to test some of the data in GeoServer, but
> I haven't done so yet.)
>
> Thanks in advance for your feedback.
>
> Roger
>
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>
>
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