How to add distance from point as an annotation in GeoDjango

I couldn't find any baked in way of doing this, so in the end I just created my own Aggregation class:

This only works with post_gis, but making one for another geo db shouldn't be too tricky.

from django.db.models import Aggregate, FloatField
from django.db.models.sql.aggregates import Aggregate as SQLAggregate


class Dist(Aggregate):
    def add_to_query(self, query, alias, col, source, is_summary):
        source = FloatField()
        aggregate = SQLDist(
            col, source=source, is_summary=is_summary, **self.extra)
        query.aggregates[alias] = aggregate


class SQLDist(SQLAggregate):
    sql_function = 'ST_Distance_Sphere'
    sql_template = "%(function)s(ST_GeomFromText('%(point)s'), %(field)s)"

This can be used as follows:

queryset.annotate(distance=Dist('longlat', point="POINT(1.022 -42.029)"))

Anyone knows a better way of doing this, please let me know (or tell me why mine is stupid)

One of the modern approaches is the set "output_field" arg to avoid «Improper geometry input type: ». Withour output_field django trying to convert ST_Distance_Sphere float result to GEOField and can not.

    queryset = self.objects.annotate(
        distance=Func(
            Func(
                F('addresses__location'),
                Func(
                    Value('POINT(1.022 -42.029)'),
                    function='ST_GeomFromText'
                ),
                function='ST_Distance_Sphere',
                output_field=models.FloatField()
            ),
            function='round'
        )
    )

You can use GeoQuerySet.distance

cities = City.objects.distance(reference_pnt)
for city in cities:
    print city.distance()

Link: GeoDjango distance documentaion

Edit: Adding distance attribute along with distance filter queries

usr_pnt = fromstr('POINT(-92.69 19.20)', srid=4326)
City.objects.filter(point__distance_lte=(usr_pnt, D(km=700))).distance(usr_pnt).order_by('distance')

Supported distance lookups

• distance_lt
• distance_lte
• distance_gt
• distance_gte
• dwithin