[postgis-users] distance between two end points of a line

[Obe, Regina]

Oops forgot to   -- verify if they are closed rings or not

SELECT cat, isclosed(wkb_geometry)
FROM spelhey 

-----Original Message-----
From: postgis-users-bounces at postgis.refractions.net
[mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of Obe,
Regina
Sent: Tuesday, September 18, 2007 7:16 AM
To: PostGIS Users Discussion
Subject: RE: [postgis-users] distance between two end points of a line

Your syntax looks right to me.  The only reason I can think why it would
return 0 is if they are closed rings.

What do the following SQL statements return

SELECT cat, length(wkb_geometry) as line_length
FROM spelhey;

SELECT cat, AsEwkt(wkb_geometry) as ewktrep
FROM spelhey;

Hope that helps,
Regina 

-----Original Message-----
From: postgis-users-bounces at postgis.refractions.net
[mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of
temiz
Sent: Tuesday, September 18, 2007 11:58 AM
To: postgis-list
Subject: [postgis-users] distance between two end points of a line

hello

I want to calculate distance between two end points of a line

I used:
select cat, 
distance(pointn(wkb_geometry,1),pointn(wkb_geometry,npoints(wkb_geometry
))) 
from spelhey;

it gives all zero

 cat | distance
-----+----------
   1 |        0
   2 |        0
   3 |        0
   4 |        0
   5 |        0
   6 |        0
   7 |        0
   8 |        0
   9 |        0
  10 |        0
  11 |        0
  12 |        0
  13 |        0
  14 |        0
  15 |        0
  16 |        0
  17 |        0
  17 |        0

can you tell me what happened ?

regards


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