[postgis-users] RV: Distance Function

[Nicolas RIBOT]

Hello Brigitte,
 
I think that the distance function works only on cartesian coordinates.
For geographic coordinates, the best way is to reproject them in a
projected coordinate system and then to measure the distance.
 
Nicolas 

-----Message d'origine-----
De : luzbrigitte [mailto:luzbrigitte at hotmail.com]
Envoyé : mercredi 18 août 2004 01:57
À : postgis-users at postgis.refractions.net
Objet : [postgis-users] RV: Distance Function



Hi, Anybody knows how can I measure in Postgis? I tried the distance
function but I don´t understand how it function, My data is in
geographical coordinates,  for example :

 

MY_TABLE

 

the_geom                                                date
hour              |  num_art

------------------------------------------------------------|-----------
-------|-----------------------|---------------

SRID=-1;POINT(-75.137956 3.566969)     | 17/08/2004 | 04:15:00 p.m.  |
1525

SRID=-1;POINT(-75.128284 3.611129)     | 17/08/2004 | 04:22:00 p.m.  |
1525

SRID=-1;POINT(-75.107022 3.639218)     | 17/08/2004 | 04:22:00 p.m.  |
1525

SRID=-1;POINT(-75.106738 3.640427)     | 17/08/2004 | 04:17:00 p.m.  |
1730

 

I need to find the distance between last 2 points for each num_art  of
the same table.

 

Anything idea to respect?

 

I have postgres 7.2.2  with postgis 0.7.3

 

Thanks a lot for your help.

 

 

Bye,

 

 

Brigitte P.

Colombia