Improving Performance... {Scanned}

[Fawcett, David]

Carola, 

Another idea with roads is that you show major highways when zoomed out
and increase detail as you zoom in.  The best way to do this is to
create separate shapefiles and layers and display them based on scale.  

Of course, it you just use the same roads shapefile and use classes to
pull out the major highways, you are only going to slow things down even
more.  

David.

-----Original Message-----
From: UMN MapServer Users List [mailto:MAPSERVER-USERS at LISTS.UMN.EDU] On
Behalf Of Steven Monai
Sent: Tuesday, March 21, 2006 11:08 AM
To: MAPSERVER-USERS at LISTS.UMN.EDU
Subject: Re: [UMN_MAPSERVER-USERS] Improving Performance... {Scanned}


Carola:

I have not personally tried it, but PostGIS provides a Simplify()
function that could be used to generate simplified datasets for use at
smaller scales. Quoted from the online manual (at
http://postgis.refractions.net/docs/ch06.html):

Simplify(geometry, tolerance)

    Returns a "simplified" version of the given geometry using the
Douglas-Peuker algorithm. Will actually do something only with
(multi)lines and (multi)polygons but you can safely call it with any
kind of geometry. Since simplification occurs on a object-by-object
basis you can also feed a GeometryCollection to this function. Note that
returned geometry might loose its simplicity (see IsSimple).


Regards,
-SM
--


On Tue, 21 Mar 2006 09:25:56 -0600, Carola Jesch <cjesch at CCT.LSU.EDU>
wrote:

>Hi All,
>Since it seems to be an issue for more than one MapServer user to 
>improve the performance I was wondering if anybody of you know some 
>good sources for getting topographic features in different spatial 
>resolutions? Lets say the roads in 1:5,000,000 1:1,000,000 1:100,000  
>or something like that? I actually don't know how to get such data 
>sets. Assuming we had it it wouldn't be a problem to use scale 
>dependency in different layers.
>
>Carola
>
>> -----Original Message-----
>> From: UMN MapServer Users List [mailto:MAPSERVER-USERS at LISTS.UMN.EDU]

>> On Behalf Of Jelmer Baas
>> Sent: Tuesday, March 21, 2006 4:27 AM
>> To: MAPSERVER-USERS at LISTS.UMN.EDU
>> Subject: Re: [UMN_MAPSERVER-USERS] Improving Performance... {Scanned}
>>
>> Rahkonen Jukka wrote:
>> > Hi Jelmer,
>> >
>> > I made a quick test with one shapefile of size 580 MB
>> containing 1.2
>> > million polygons. Shptree (from FW Tools 0.9.8) with default 
>> > parameters took 2 min 30 secs to run with 3 GHz Pentium and
>> Windows XP
>> > and memory usage grew not more than 200-300 MB during the process. 
>> > Of my 1 GB I had all the time more than 500 free. The idle
>> usage seems
>> > to be around 200 MB.
>>
>> Hmm, for some reason the file that I mentioned earlyer DOES work. I 
>> probably used a different file for testing, though I can't remember 
>> which one.
>>
>> Can you comfirm if the SHP+index is faster than the .TAB file?
>>
>> --
>> Jelmer
>>