Jehiah Czebotar wrote: > I should explain a little more what i am trying to do. I'm trying to > draw a circle with a constant radius as expressed in miles (not pixels > or lat/lon distance).
Go it. > The problem i was having is that when plotting an elipse closer > towards the poles it does not have the correct geometry to the north > and south of the center point.. Yes -- at that scale, you're going to have problems. IT works fine for smaller scale stuff (~100s of miles) > I was hoping that a different projection function would help resolve > that ( i don't care if it isn't perfect, it just need to be a little > better) Well, I don't know the properties of all projections, but when you're looking at that much of the earth on a flat surface, there are going to be substantial distortions. Different projections have different properties (equal angle, equal area, etc). you could choose one that ws centered on the middle of your circle that would work, but if you have circles in different places, then that won't help. If you poke around the net for info on projections, you may find one that's OK, and you can probably use it from python through the PROJ4 library, and we can alter FloatCanvas to accommodate that, but frankly, that seems like a lot of work! > As a work around I've found that drawing a polygon with 360 points > calculated at each radian from the center of my circle actually works > out pretty well. Yes, it should, and indeed, that's not really a work-around. I think it's the right way to do it. That's what GIS systems do. You may not need the full 360 points -- how does it look with 180? 90? Anyway, I'd go with that. You could make a custom DrawObject that has the Circle interface, and computed a polygon in lat-long points instead. Are you using Circular (or even better ellipsoidal) geometry to calculate your points? -CHB -- Christopher Barker, Ph.D. Oceanographer Emergency Response Division NOAA/NOS/OR&R (206) 526-6959 voice 7600 Sand Point Way NE (206) 526-6329 fax Seattle, WA 98115 (206) 526-6317 main reception [EMAIL PROTECTED] _______________________________________________ FloatCanvas mailing list [email protected] http://mail.mithis.com/cgi-bin/mailman/listinfo/floatcanvas
