Stephen Woodbridge schrieb:
Nicklas Avén wrote:
Hallo
I have a quite big dataset (approx 1.2 mill rows) with roads. What I
would like to to is merging all linestrings between crossings so I
get one linestring between two crossings or between a crossing and
the end of the road. Now there can be many small parts cut by a
bridge or some border. For quality I also have to check so no
linestrings are just passing a crossing too, but that is secondary
because I don't think that is a problem with this dataset.
A while ago I saw a solution on this list which included merging all
and dumping, but I think that will be a little heavy in this case.
I have been struggling some with recursive queries but I haven't
found the way.
How to do it?
Nicklas,
If I understand what you want correctly, the problem is probably best
solved, by something like the following:
1) assign unique nodes to all segment end points and add start_node_id
and end_node_id to all your edges. look at pgRouting this have code to
do this already implemented.
vertex_ids table
uid, lat, lon
2) add a num_segments column to you unique node table
3) update vertex_ids set num_segments=(select count(*) from edges e
where e.start_node_id=uid or e.end_node_id=uid);
now num_segments will tell you what you need to know
num_segments
0 - should not happen
1 - these are dead end streets
2 - these are joinable segments
3+ - these are crossing segments
For the joinable segments create a new joined segment use the segments
select * from edges
where e.start_node_id=<uid_in_question>
or e.end_node_id=<uid_in_question>;
insert that, and delete the two old segments and fixup your node counts.
-Steve
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Hi
I think I have the same problem!
Are there any ideas how I can construct an SQL script that join
streets-->merging linestrings that are not joined?
So a user often build street, that endnodes are not joined with the
other street. So, if the endnode is an a buffer to a digitized
street-->the sql will join this line?!
Is there a way to do this?!
--daniel
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