[postgis-users] line simplication

[Eric L. Blevins]

----- Original Message -----
From: "Daniel Morissette" <morissette at dmsolutions.ca>
To: "PostGIS Users Discussion" <postgis-users at postgis.refractions.net>
Sent: Wednesday, January 08, 2003 11:21 AM
Subject: Re: [postgis-users] line simplication


> "Eric L. Blevins" wrote:
> >
> > A simplification function that accepts the geometry and a factor of how
much
> > to simplify will be very usefull to anyone using applications like
> > mapserver.
> > With this function I think I could decrease the rendering time of my
maps by
> > an order of magnitude while still producing quality maps.
> >
>
> Just a quick note to let you know that MapServer already 'simplifies'
> the shapes before passing them to the rendering code so the gain in
> performance may not be as big as you expect.  With a simplify()
> function at the database end you would slightly reduce the time to
> transfer the shapes from PostGIS to MapServer and to package them as
> shapeObj initially in MapServer, but you would not save any time in the
> rendering code since MapServer already does its own simplification based
> on the pixel size of the output image.
>
> Daniel
> --
> ------------------------------------------------------------
>  Daniel Morissette               morissette at dmsolutions.ca
>  DM Solutions Group              http://www.dmsolutions.ca/
> ------------------------------------------------------------
>
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>
I was unaware that mapserver did that.

But knowing that I still believe a simplification function in the database
would boost performance for large datasets.

As you stated time would be saved transferring the data to mapserver and
time would be saved by mapserver dealing with less data when it packages it
into ShapeObj.  When using a large dataset the time saved could be
significant.

Eric L. Blevins
www.WiFiMaps.com