Generate a viewport bias from a GeoDjango model. Useful when geocoding.

GeoDjango model with viewport bias.py

from django.contrib.gis.db import models
from django.contrib.gis.geos import Point

class Multipolygon(models.Model):
  """
  Try using it with this: http://github.com/palewire/latimes-mappingla-geopy
  """
  name = models.CharField(max_length=200, null=True, blank=True)
  multipolygon = models.MultiPolygonField(srid=2229, null=True, blank=True)
  objects = models.GeoManager()
  
  def __unicode__(self):
    return self.name
  
  class Meta:
    ordering = ('name',)
  
  def get_viewport(self):
    if not self.multipolygon:
      return None
    xmin, ymin, xmax, ymax = self.multipolygon.extent
    x, y = self.multipolygon.centroid.tuple
    min_radius = Point(x, y).distance(Point(xmin, ymin))
    max_radius = Point(x, y).distance(Point(xmax, ymax))
    return {
      'centroid': { 'y': y, 'x': x },
      'span': { 'min': min_radius, 'max': max_radius }
    }
  viewport = property(get_viewport)