[postgis-users] Calculation distance between two points

[Nicklas Avén]

Hallo Eike

The issue here is, latitude-longitude vs longitude-latitude.

In PostGIS the order is longitude latitude


So if you reverse the order of the coordinates you will get about 539
meters.

What is right or wrong depends on which one is longitude and which one
is latitude.

Another way to write your query in 1.5 is casting to geography

So, to compare the two orderings:

SELECT
 ST_Distance('POINT(52.278888888889
8.0430555555556)'::geography,'POINT(52.2812598 8.036165)'::geography),
 ST_Distance('POINT(8.0430555555556
52.278888888889)'::geography,'POINT(8.036165 52.2812598)'::geography)





HTH
Nicklas




On Wed, 2011-01-19 at 06:40 -0800, iKey wrote:
> Dear Community,
> 
> I want to calculate the distance between two points with a postgres query.
> The point reference system of my DB is epsg 4326. As far as I know I have to
> transform them, because with
> WGS84 4326 I can calculate the distance in radian only.
> 
> This is an example query in that I try to calculate the distance in
> different ways, but with no luck so far :(
> SELECT	ST_Distance(ST_Transform(ST_GeomFromText('POINT(52.278888888889
> 8.0430555555556)',4326),
> 900913),ST_Transform(ST_GeomFromText('POINT(52.2812598 8.036165)', 4326),
> 900913))
> 	,ST_Distance_Sphere(ST_GeomFromText('POINT(52.278888888889
> 8.0430555555556)',4326), ST_GeomFromText('POINT(52.2812598 8.036165)',
> 4326))
> 	,ST_Distance_Spheroid(ST_GeomFromText('POINT(52.278888888889
> 8.0430555555556)',4326), ST_GeomFromText('POINT(52.2812598 8.036165)',
> 4326), 'SPHEROID["WGS 84",6378137,298.257223563]')
> FROM pois 
> LIMIT 1;
> 
> The results look like this
> 818.392971975843;
> 809.44384291019;
> 805.637737963218
> 
> When i calculate the distance in GoogleEarth or GoogleMaps I get a result
> about 538,06m, so I think there is going something wrong in my
> calculation with postgres.
> 
> Does anyone has any ideas whats going wrong or what else I can try?
> 
> Best regards
> Eike