GeoDjango: How to create a circle based on point and radius

Yes, it is possible to use the geos buffer method:

>>> from django.contrib.gis import geos>>> center = geos.Point(5, 5)>>> radius = 2>>> circle = center.buffer(radius)>>> circle<Polygon object at 0x1029d8370>

The radius here is in the same units as the coordinates of the points. This will work for some coordinate systems like UTM, but not as well for others.

Also, while this is appropriate for constructing a circular geometry, the PostGIS documentation notes that for doing radius searches ST_DWithin is more efficient.

I spent a ridiculous amount of time trying to get this working. Since this is the number one google search result, here's what worked for me:

radius_km = radius*1.609 # convert miles to kmpoint = target.geolocation # a django PointField using SRID 4326# re-project point to a flat coordinate system # so we can use meters instead of degrees below, # AND get an actual circle instead of oval    point.transform(6347) poly = point.buffer(radius_km*1000) # get a circular polygon from radiuspoly.transform(4326)# re-project the resulting polygon back

Bonus: If you're doing this so you can get a circle on a google static map, grab polyline:

import polylineimport astgeo = ast.literal_eval(poly.geojson) # turn the text into a dictpoints = geo['coordinates'][0]pl = polyline.encode(points, geojson=True, precision=5) # make a polyline out of the polygon for googlemap_url += '&path=color:0x00000000%7Cfillcolor:0x0000AA33%7Cweight:1%7Cenc:' + pl