Andrew,
Not sure I understand your question. Are you saying your street segments are
cut such that they only connect at junctions. Kind of like tiger tlids.
And given each intersection, you are trying to find continguous segments from
the intersection?
e.g.
----------- ------------- --------------- Intersection
-------------------------- ------------------------------- -----------------
t3 t2 t1
s3 s4 sn
|a1
|a2
|an
So you would keep on collecting segments as long as they are connected to the
previous ones?
Thanks,
Regina
________________________________
From: postgis-users-boun...@postgis.refractions.net
[mailto:postgis-users-boun...@postgis.refractions.net] On Behalf Of Andrew Ross
Sent: Saturday, December 13, 2008 11:05 AM
To: postgis-users@postgis.refractions.net
Subject: [postgis-users] Crossing roads
Hi Everybody,
I hope I'm posting to the right location (I just subscribed to this list). I
have sent this question before but have not seen it listed anywhere yet.
In any case, I have a road network in which all of the street segments are
snapped together. I need to group all of the line segments of two streets that
cross each other (street 1 and street 2 as shown below) into 4 groups of
segments defined as all of those located on either side of the intersection,
(street segments A, street segments B, street segments C and street segments D,
as shown at the bottom).
Can anybody give me a high level idea of what functions / methods can be used
to achieve this?
I’ve gotten as far as identifying the 4 segments actually connected to the
intersection using the ST_Intersection function.
How would I get all other segments connected to these 4?
Do I have to write a recursive function using ST_Touches ? I’d rather not if
there is a more elegant way of doing this.
Thanks in advance,
Andrew
1
1
1
1
222222222222 X 22222222222222
1
1
1
1
A
A
A
A
BBBBBBBBBBXCCCCCCCCCCC
D
D
D
D
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