I use .extra(where=[where]) and something like this (measures km, not miles): ( 6378.137 * acos( cos( radians(long) ) * cos( radians( latitude ) ) * cos( radians( longitude ) - radians(lat) ) + sin( radians(long) ) * sin( radians( latitude ) ) ) ) < 10
latitude and logitude are db-fields, 6378.137 the radius of the earth, long/lat my current position, searches for objects in a 10 km circle regards Henrik >reply to message: >date: 30.07.2010 07:30:30 >from: "Jani Tiainen" <rede...@gmail.com> >to: django-users@googlegroups.com >subject: Re: Best way to find near people > >> On Jul 29, 2010, at 2:58 PM, Alexandre González wrote: >> > Hi! >> > >> > I'm searching near people in my app. I'm doing it a this way: >> > >> > 37 people = Person.objects.all().exclude(user=request.user) >> > 38 >> > 39 near_people = list() >> > 40 for person in people: >> > 41 if self.is_near(me.coordinates, person.coordinates): >> > near_people.append(person) >> > >> > Now, I'm getting all the the Person objects. This is a inefficient way. >> > >> > The coordinates are latitude/longitude coordinates, so I think in test >> > the variation and get only latitude +/- 1 and longitude +/- 1 and after >> > this, do the test exactly (the funcion is_near). >> > >> > But instead this, can I "draw" a circle and search only Person objects >> > inside it? >> >> I'm not sure what database you are using, but if you are using PostgreSQL, >> it has built-in geometric operators specifically for this kind of thing. >> You might have to drop down into SQL, but in 1.2, that's nice and easy. >> >> The PostgreSQL documentation on this is at: >> >> http://www.postgresql.org/docs/8.4/interactive/datatype-geometric.html >> -- >> -- Christophe Pettus >> x...@thebuild.com > >Or if spatial operations are really needed, why not to use real spatial >database and GeoDjango (django.contrib.gis). Spatialite, Postgis, Mysql or >oracle. All supports at spatial to some extent. And there you can do easily >simple filtering: > >Person.objects.filter(person_coordinates__dwithin(me.coordinates, distance)) > >..and geodjango + spatial engine behind it will take care of all that complex >stuff. > >Note: you can still use GEOS parts from geodjango to do calculations so you >don't have to reinvent wheel if you want to keep coordinates as you already >have. > >-- > >Jani Tiainen > >-- >You received this message because you are subscribed to the Google Groups >"Django users" group. >To post to this group, send email to django-us...@googlegroups.com. >To unsubscribe from this group, send email to >django-users+unsubscr...@googlegroups.com. >For more options, visit this group at >http://groups.google.com/group/django-users?hl=en. > -- You received this message because you are subscribed to the Google Groups "Django users" group. To post to this group, send email to django-us...@googlegroups.com. To unsubscribe from this group, send email to django-users+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/django-users?hl=en.
