[Mapserver-users] please give me an advice on this !

[Vincent Schut]

Petur,

(first: please reply to all when replying on a list message. Others might want 
to join the discussion, or at least learn from it...)

I'll try, though I'm not an expert. But if you ask expert-questions on this 
list, you'll get expert-answers for sure... That's the way this list works 
:-)

a shapetree is basically a spatial index for all shapes in a shapefile. It 
enables mapserver to do a fast search on this index first, to check which 
shapes are inside the requested bounding box, and only after that acces these 
shapes to check whether they should be rendered, and eventually draw them. It 
saves you a lot of time since otherwise mapserver always has to do a 
sequential search of the entire shapefile(s).
Tiling means you split up your dataset in several different tiles (spatial 
subsets). It essentially means less overhead in accessing large files. When a 
certain zoomlevel is requested, not the entire shapefile has to be read, but 
only the few tiles that fall inside the requested extent.
A careful combination of both can enhance mapserver performace considerably, 
as has been testified in several posts on this list.
Read more:
http://mapserver.gis.umn.edu/doc36/utils.html, contains info about the shptree 
and tile4ms programs.
If you want to use these, probably the best way is to experiment a bit to get 
accustomed to these utilities. I do not have much experience with them, so 
I'm afraid I can't help you much with that. I hope, however, that the general 
idea is clear now.

Regards,
Vincent Schut.


On Tuesday 25 March 2003 13:56, you wrote:
> could you explain really short, what shapetrees and tiles are ?
>
>
> ----- Original Message -----
> From: "Vincent Schut" <schut at sarvision.com>
> To: "Petur Kirke" <peturkirke at fds.fo>; "MapServer"
> <mapserver-users at lists.gis.umn.edu>
> Sent: Tuesday, March 25, 2003 2:41 PM
> Subject: Re: [Mapserver-users] please give me an advice on this !
>
> > Petur,
> >
> > that depends on so many things you don't provide information about, that
>
> it
>
> > really is impossible to answer your question now.
> > E.g. for performance of mapserver the spatial extent (1400 km) is not so
>
> much
>
> > the issue, but for example things like the complexity of your shapes, how
> > many layers / classes do you have (if you have these), how are your
> > shapes organized, what is the size (in bytes, not in meters) of your
> > data, what
>
> kind
>
> > of requests will your users do, will they zoom in much or rather use a
>
> view
>
> > of the entire extent, etc. etc.
> > Usually it is better to just start simple, and don't think about
>
> performance.
>
> > Once you got things working, start improving the performance by using
> > shapetrees, tiles, etc. You will be able to find quite some usefull
> > information about several performance issues (there is no 'generic best
>
> way'
>
> > to organize things, all depends on your data and your application) on the
> > mapserver home/wiki pages and by searching the archives of this
>
> mailinglist (
>
> > http://mapserver.gis.umn.edu/cgi-bin/wilma/mapserver-users ).
> >
> > Hoping to have helped you a bit in the right direction...
> >
> > Regards,
> > Vincent Schut.
> >
> > On Tuesday 25 March 2003 13:19, Petur Kirke wrote:
> > > I want to make a Map Server application containing a map, that has a
>
> size
>
> > > of 1.400 kilometers square.
> > >
> > > We usually use Microstation, and we have the maps stored in many
>
> different
>
> > > files.
> > > Now I convert the files to shp.
> > >
> > > Now to my question:
> > > When I use Map Server is it possible to have the maps stored in many
>
> files,
>
> > > or would it be better to store this map with a size of 1.400 kilometers
> > > square in one single file ?
> > >
> > > _______________________________________________
> > > Mapserver-users mailing list
> > > Mapserver-users at lists.gis.umn.edu
> > > http://lists.gis.umn.edu/mailman/listinfo/mapserver-users
> >
> > --
> > ______________________________________
> > Vincent Schut (schut at sarvision.com)
> > Sarvision B.V.
> > Wageningen, The Netherlands
> > www.sarvision.com

-- 
______________________________________
Vincent Schut (schut at sarvision.com)
Sarvision B.V.
Wageningen, The Netherlands
www.sarvision.com