[OpenLayers-Users] Circles

[Tim Schaub]

Hey-

Heidt, Christopher M. wrote:
> this is definitly a clever aproach, but it is still a work-around for 
> what i consider to be a basic shape.
> I just wonder why i cant have something along the lines of: new 
> Openlayers.Geometry.Circle(lon,lat,radius);

Would you expect this to be a circle on the ground or a circle on your 
map?  If the former, you'd be disappointed.

Not sure if it has been mentioned in this thread, but if you want a 
regular polygon with many sides (approximating a circle), you can use 
the OpenLayers.Polygon.createRegularPolygon method [1].  See the modify 
feature example for use (and set the number of sides to 30 or so) [2].

Tim

[1] 
http://dev.openlayers.org/apidocs/files/OpenLayers/Geometry/Polygon-js.html#OpenLayers.Geometry.Polygon.createRegularPolygon

[2] http://openlayers.org/dev/examples/modify-feature.html


> ------------------------------------------------------------------------
> *From:* Estanislao Gonzalez [mailto:estanislao.gonzalez at isst.fraunhofer.de]
> *Sent:* Mon 12/8/2008 11:47 AM
> *To:* Heidt, Christopher M.
> *Subject:* Re: [OpenLayers-Users] Circles
> 
> That's not true. You can always recalculate the circle radius when
> changing the zoom. That's what I did and had no problem at all.
> 
> //radius unit is in kilometers
> var DOTS_PER_UNIT = OpenLayers.INCHES_PER_UNIT.km *
> OpenLayers.DOTS_PER_INCH;
> 
> // 5 km radius
> var circleRadius = 5;
> 
> "default": new OpenLayers.Style({
>             pointRadius: "${radius}"
>         }, {
>             context: {
>                 radius: function(feature){
>                     //very rough. Be sure it is at least somehow correct.
>                     var rad = circleRadius * DOTS_PER_UNIT /
> feature.layer.map.getScale();
>                     return rad;
>                 }
>             }
>       
>         });
> 
> Still I didn't check if the measurement is right, but it is constant. So
> you might have to multiply it by a constant if required (probably by
> adapting DOTS_PER_UNIT).
> 
> Note that I'm reading the radius from a feature in a WFS layer, so you
> might have to change that as well (feature.attributes.radius)
> 
> Hope it helps,
> 
> Regards,
> Estani
> 
> Heidt, Christopher M. schrieb:
>  > right, changing a points radius in the style makes the marker that 
> represents a point larger, but it isnt a "Circle" Feature because it 
> remains the same size when u zoom in and out.
>  >
>  > oracle has a WKT outputer that makes a CURVEPOLYGON(# #,# #,# #,# #) 
> or some such nonsence to represent circles. the problem is that it isnt 
> part of the WKT spec so nothing supports it.
>  >
>  > I'd change it to a format that is supported,
>  > but i can't find anything in any format that can represent a circle.
>  > Anybody know if it would be a daunting task to add CURVEPOLYGON 
> support to the WKT parser?
>  >
>  > ________________________________
>  > From: users-bounces at openlayers.org on behalf of Lehtonen, Mika
>  > Sent: Tue 12/2/2008 2:23 PM
>  > To: Didrik Pinte
>  > Cc: users at openlayers.org
>  > Subject: Re: [OpenLayers-Users] Circles
>  >
>  >
>  > Hi Didrik,
>  >
>  > I guess the points are still points regardless of their style? So you
>  > can't use their geometry as a replacement of a circle?
>  >
>  > - mika -
>  >
>  > Didrik Pinte kirjoitti:
>  >  
>  >> On Tue, 2008-12-02 at 08:27 -0500, Heidt, Christopher M. wrote:
>  >>
>  >>    
>  >>> Probably a dumb question, but how can I create a circle feature using
>  >>> the api?
>  >>>
>  >>> I'm hoping you're not going to say I have to generate a bunch of
>  >>> points an make a polygon :(
>  >>>
>  >>>      
>  >> Using a point with a style using a radius will do it fine.
>  >>
>  >> For example :
>  >> http://openlayers.org/dev/examples/stylemap.html
>  >>
>  >> Didrik
>  >>
>  >> ------------------------------------------------------------------------
>  >>
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> 
> 
> --
> Dipl.-Kfm. Estanislao Gonzalez, Fraunhofer-Institut für Software- und 
> Systemtechnik ISST
> Location-based Services, Steinplatz 2, 10623 Berlin, Germany
> Telefon: +49 (0) 30 / 2 43 06-3 36
> mailto:estanislao.gonzalez at isst.fraunhofer.de
> www.isst.fraunhofer.de
> 
> 
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-- 
Tim Schaub
OpenGeo - http://opengeo.org
Expert service straight from the developers.