gis.py

from django.contrib.gis.measure import D
from django.contrib.gis.geos import Point
SRID = 4326
pnt = Point(lat, lon, srid=SRID)

class Location(models.Model):
    point = models.PointField()
    objects = models.GeoManager()

campuses = Location.objects.filter(
    point__distance_lte=(pnt, D(mi=1)))
    
# raises: "distance_lte is not a valid spatial lookup for PointField"