We are starting to use geodjango (revision 7003) and are having
problems using the api to calculate distance.
class Airport(models.Model):
icao = models.CharField('ICAO', max_length=4)
location = models.PointField()
The location field will eventually be populated using lat/longs from a
text file.
For now, I populated 3 records in the table:
Airport.objects.create(icao="KBWI",
location=fromstr('POINT(-76.668333333333337 39.175361111111108)',
srid=4326))
Airport.objects.create(icao="KDEN",
location=fromstr('POINT(-104.67317777777778 39.861655555555558)',
srid=4326))
Airport.objects.create(icao="EGLL",
location=fromstr('POINT(-0.4613888888888889 51.477499999999999)',
srid=4326))
When I try to use the api to get distance, I do not get the correct
results:
point = Airport.objects.get(icao="KBWI").location
for airport in Airport.objects.distance(point):
print airport.icao + ": " + str(airport.distance) + ", " +
str(Distance(degree=airport.distance).nm)
EGLL: 77.1935295397, 0.000727473678024
KBWI: 0.0, 0.0
KDEN: 28.0132524428, 0.000263997564426
select icao, ST_distance(ST_GeomFromText('POINT(-76.668333333333337
39.175361111111108)',4326), location) from common_airport;
icao | st_distance
------+------------------
KBWI | 0
KDEN | 28.0132524427637
EGLL | 77.1935295397234
select icao,
distance_sphere(ST_GeomFromText('POINT(-76.668333333333337
39.175361111111108)',4326), location) from common_airport;
icao | distance_sphere converting manually to nm
------+----------------------
KDEN | 2393555.0105449 1292.41631
KBWI | 2.81660258041303e-10 0
EGLL | 5833168.46744864 3149.65875
Using distance_sphere, I get the correct results. Is there any way to
use the django api to get distance_sphere?
I also tried using the SRID 32140:
class Airport(models.Model):
icao = models.CharField('ICAO', max_length=4)
location = models.PointField(32140)
I used the same code to populate the records - it's nice that
geodjango can do that.
When I try to use the api to get distance, I get closer results, but
they're still not correct:
point = Airport.objects.get(icao="KBWI").location
for airport in Airport.objects.distance(point):
print airport.icao + ": " + str(airport.distance) + ", " +
str(Distance(meter=airport.distance).nm)
EGLL: 6258767.81814, 3379.46426466
KBWI: 0.0, 0.0
KDEN: 2442966.58517, 1319.09642828
Is there any way to use the django api to get the distance?
Versions:
WhiteBox Enterprise Linux 3.0 (clone of Red Hat enterprise 3.0)
gcc 3.2.3 / glibc 3.2.3
Python 2.4.2
ctypes 1.0.2
PostgreSQL 8.2.4
postgis 1.3.2
geos 3.0.0
proj4 4.6.0
curl 7.17.1 (needed for gdal)
expat 2.0.1 (needed for gdal)
gdal 1.5.0
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