Correct. It looks like the below query will return coincident lines along contiguous sections of 3 or more (it also
assumes your network is properly directionalized).
This is a problem of transitive closure. I once solved this iteratively by first finding all the degree-2 nodes in my
network, then one node at at time, merging the two lines that share the node.
A modern approach might be to solve this using PostgreSQL's new recursive SQL
syntax.
Cheers,
Kevin
Martin Fafard wrote:
Stanley
Thank you
But your query merge two contiguous lines but not 3 or more contiguous
lines...
Martin
Sufficool, Stanley a écrit :
Does this look correct?
select st_linemerge(st_collect(cs1.the_geom))
from (
select the_geom, st_startpoint(cs_s.the_geom) as linepoint
from mylinetable cs_s
UNION ALL
select the_geom, st_endpoint(cs_e.the_geom) as linepoint
from mylinetable cs_e
) as cs1
group by linepoint
having count(*) = 2
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