django-georangefilter

Python function that will annonate your queryset using Postgres earth_box and ll_to_earth functions that allow filtering in range N kilometers from given latitude/longitude point.

IMPORTANT:
https://www.postgresql.org/docs/devel/static/earthdistance.html

In this module, the Earth is assumed to be perfectly spherical. (If that's too inaccurate for you, you might want to look at the PostGIS project).

pip install git+https://github.com/bukowa/django-georangefilter

Results for filtering in 15km radius, with second circle 30km radius, as you can see its pretty inaccurate.

If you want to test in your custom radius, take a look at tests.py file.

For example, given model:

class City(models.Model):
    longitude = models.FloatField(db_index=True)
    latitude = models.FloatField(db_index=True)
    def in_range(self, range_in_meters, **kwargs):
        return filter_in_range(
            queryset=self.__class__.objects,
            latitude=self.latitude,
            longitude=self.longitude,
            range_in_meters=range_in_meters,
            latitude_column_name="latitude",
            longitude_column_name="longitude",
            **kwargs,
            )

Get all cities in range 10km from city:

    city = City.objects.all()[0]
    cities_in_range = city.in_range(10000)

How the sql query really looks like:

{'sql': 'SELECT "app_city"."longitude", "app_city"."latitude", earth_box(ll_to_earth(51.03923, 16.97184), 10000) AS "earthbox" FROM "X" WHERE earth_box(ll_to_earth(51.03923, 16.97184), 10000) @> (ll_to_earth("X"."latitude", "X"."longitude")) LIMIT 21', 'time': '0.004'}

Requires cube and earthdistance extensions. To enable them you can:

    operations = [
        CreateExtension("cube"),
        CreateExtension("earthdistance"),
        # you can also create an index like that:
        migrations.RunSQL(
            "CREATE INDEX indexname ON yourapp_yourmodel USING gist(ll_to_earth(latitude_column_name, longitude_column_name));"
        ),
    ]

or

from django.db import connection
cursor = connection.cursor()
cursor.execute("CREATE EXTENSION cube;")
cursor.execute("CREATE EXTENSION earthdistance;")

How the functions looks like:

def filter_in_range(
    queryset: QuerySet,
    latitude: float,
    longitude: float,
    range_in_meters: int,
    latitude_column_name: str = "latitude",
    longitude_column_name: str = "longitude",
    field_name: str = "earthbox",
    lookup_exp: str = "in_georange",
):
    earthbox = {field_name: EarthBox(LLToEarth(latitude, longitude), range_in_meters)}
    lookup = "%s__%s" % (field_name, lookup_exp)
    in_range = {lookup: LLToEarth(latitude_column_name, longitude_column_name)}
    return queryset.annotate(**earthbox).filter(**in_range)

data for map generation used from geonames.org