[mapserver-users] Dynamically draw different sized ellipses on map

[Fawcett, David (MPCA)]

It sounds like you really want to define polygons in an orthogonal projection and then re-project them to geographic to show the distortion.  Unless you calculate the appropriate distortion for a particular coordinate and then can pass in the x and y radii for an ellipse symbol, I think that you will need to use polygon features instead of points.  

You have probably already seen the symbol construction page, but here it is:  http://mapserver.org/mapfile/symbology/construction.html#sym-construction

Matt Perry wrote kind of a cool example Python script that creates the kind of polygons that you are looking for.  This won't work with the way that you are doing things, but it might give you some concepts and ideas.

http://www.perrygeo.net/wordpress/?p=4

David.

-----Original Message-----
From: mapserver-users-bounces at lists.osgeo.org [mailto:mapserver-users-bounces at lists.osgeo.org] On Behalf Of stoli
Sent: Tuesday, September 07, 2010 5:00 PM
To: mapserver-users at lists.osgeo.org
Subject: [mapserver-users] Dynamically draw different sized ellipses on map


Was hoping on some guidance as to the best way to attack this... 

My app uses the cgi interface. I have been succesful at drawing lines, 
squares and small circles on the fly by sending mods to the .map file via 
the URL. I have been doing this by dynamically adding points to various 
POINT layers with the afforementioned symbols. Up to this point, the squares 
and circles have been uniform in size and aspect. Now I find myself needing 
to add multiple ellipses of varying sizes at different locations on the map. 
Technically they would be circles of area, but the aspect will change as the 
location approaches the poles. (almost a true circle at the 
equator and verly long ellipse toward the poles due to map projection). 
Ideally the ellipses will be filled with either a hatch pattern or a 
transparent solid color. 

Any suggestions as to the best way to accomplish this? 

Cheers 

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