[postgis-users] Re: distance query is not returning expected result

[Jimmy Forrester-Fellowes]

Hi, just an update on this, found the solution thanks to user: nhv on
#postgis. I was setting the long & lat the wrong way round when creating my
points and instead of doing all the transforming and stuff I've just used
st_distance_sphere().

Solution below:

SELECT ST_Distance_Sphere(
    ST_SetSRID(ST_Point(-1.54911, 53.7996374 ), 4326),
    ST_SetSRID(ST_Point(-1.0822855, 53.9577018), 4326)
  ) / 1000;

I know it can be more accurate using ST_Distance_Spheroid() but i need speed
over precise accuracy in this case.

Thanks,
- Jimmy


On Sun, Jan 25, 2009 at 3:03 PM, Jimmy Forrester <
jimmy at sparkleinteractive.co.uk> wrote:

> Hey all, I'm new to postgis and implementing a few geographic features in
> to my site. I'm having a bit of difficulty getting my distance calculations
> working:
>
> select ST_Distance(    ST_Transform(ST_SetSRID(ST_Point(53.7996374,
> -1.54911),     4326), 2163),
>             ST_Transform(ST_SetSRID(ST_Point(53.6451179, -1.784876),
> 4326), 2163)
>         ) / 1000
>
>
> In the query above I'm testing the distance between Leeds & Huddersfield.
> I'm trying to convert the 4326 srid geom to  srid 2163 which is meters (i
> think!). For an unknown reason this is returning 64 km which i know is
> incorrect.
>
> I've plotted the coords on google maps and they are definitely correct,
> google maps says the distance is about 24 km. see:
>
>
> http://www.google.com/maps?f=d&source=s_d&saddr=53.7996374,+-1.54911&daddr=53.6451179,+-1.784876&hl=en&geocode=FdXqNAMdylzo_w%3BFT6PMgMd1MPk_w&mra=ls&dirflg=w&doflg=ptk&sll=53.722107,-1.645889&sspn=0.161297,0.418854&ie=UTF8&ll=53.72231,-1.667175&spn=0.161296,0.418854&t=h&z=12
>
> Any help on this would be great,
>
> Thanks,
> Jimmy
>
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