def save(self, commit=True):
obj = super(LocationAnswer, self).save(commit=False)
if obj.value:
obj.latitude, obj.longitude = get_latitude_and_longitude(obj.value)
if commit:
obj.save()
return obj
return None
def _extra_from_distance(filter, submission_id_column):
""" This uses the Spherical Law of Cosines for a close enough approximation
of distances. distance = acos(sin(lat1) * sin(lat2) +
cos(lat1) * cos(lat2) *
cos(lng2 - lng1)) * 3959
The "radius" of the earth varies between 3,950 and 3,963 miles. """
spaces = re.compile(r'\s')
key = spaces.sub("+", "lat_lng_of_" + str(filter.location_value.lower()))
lat_lng = cache.get(key, None)
if lat_lng is None:
lat_lng = get_latitude_and_longitude(filter.location_value)
cache.set(key, lat_lng)
(lat, lng) = lat_lng
if lat is None or lng is None:
return
acos_of_args = (
sin(_radians(lat)),
_D_TO_R,
cos(_radians(lat)),
_D_TO_R,
lng,
_D_TO_R)
acos_of = (
"%f * sin(latitude / %f) + "
"%f * cos(latitude / %f) * "
"cos((longitude - %f) / %f)") % acos_of_args
# if acos_of >= 1 then the address in the database is practically the
# same address we're searching for and acos(acos_of) is mathematically
# impossible so just always include it. If acos_of < 1 then we need to
# check the distance.
where = "".join((
submission_id_column,
" IN (SELECT ca.submission_id FROM ",
"survey_answer AS ca JOIN survey_submission AS cs ",
"ON ca.submission_id = cs.id ",
"WHERE cs.survey_id = %s AND latitude IS NOT NULL ",
"AND longitude IS NOT NULL AND ",
acos_of,
" >= 1 OR (",
acos_of,
" < 1 AND 3959.0 * acos(",
acos_of,
") <= %s))"))
params = [int(filter.field.survey_id), int(filter.within_value)]
return where, params
