Improving Performance... {Scanned}

[Steven Monai]

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
>>