Reduce Detail on Maps?

Steve Lime steve.lime at DNR.STATE.MN.US
Wed Aug 10 11:01:29 EDT 2005

I was talking about potentially adding an option to the [shpxy ...] tag to thin shapes using the Douglas-Peuker algorithm. It's vaporware at this point though. I did post a perl MapScript script that implements that algorithm on shapefiles. It's on the WIKI. It's not speedy (which is why on-the-fly application is a bad idea, at least for drawing) but is certainly suitable for offline use.


>>> Bart van den Eijnden <BEN at SYNCERA-ITSOLUTIONS.NL> 08/10/05 1:51 AM >>>
I remember Steve talking about feature thinning in Mapserver at the MUM2.

Best regards,

Bart van den Eijnden
Syncera IT Solutions
Postbus 270
2600 AG  DELFT 015-7512436
email: BEN at
>>> Abe Gillespie <abe.gillespie at GMAIL.COM> 08/09/05 23:31 PM >>>
I assumed Kyle was looking for a way to antialias the jaggedness of the lines.


On 8/9/05, Gregory S. Williamson <gsw at> wrote:
> Kyle,
> Do you mean to reduce the detail in the lines themselves ?
> If you are using postgres you could perhaps use the simplify function:
> * 0.60 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)
> Not sure what other tools could do this ... perhaps the JUMP tool has such functionality as well, and it can work directly with shape files.
> HTH,
> Greg Williamson
> GlobeXplorer LLC
> -----Original Message-----
> From:   UMN MapServer Users List on behalf of Kyle Mulka
> Sent:   Tue 8/9/2005 12:56 PM
> Cc:
> Subject:        [UMN_MAPSERVER-USERS] Reduce Detail on Maps?
> Is there any way to reduce the detail and smooth out lines. This:
> FFFF&TRANSPARENT=TRUE&SRS=EPSG:4326&BBOX=-83.7322998046875,42.27934093085314
> 5,-83.72955322265625,42.28137302193453&WIDTH=256&HEIGHT=256
> Just looks ugly with all the detail in it.
> -Kyle Mulka
> !DSPAM:42f90a033852046723401!

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