362 reputation
212
bio website N/A
location Edinburgh
age 30
visits member for 2 years, 3 months
seen Apr 15 at 12:34

Working with and discovering geo-information :)


Feb
6
asked Vertex point is returning None
Feb
2
comment Passing parameters to PostGIS SQL queries in Python: weird behaviour
Yeap, I have excausted coding alternatives based on this document initd.org/psycopg/docs/usage.html#query-parameters..
Feb
2
comment Passing parameters to PostGIS SQL queries in Python: weird behaviour
Hi, yes I tried hard coding it and still does not work...
Feb
2
asked Passing parameters to PostGIS SQL queries in Python: weird behaviour
Jan
27
comment clip linestring by length
You are right, some of my lines have a double ending like a double fork and that is probably causing trouble to postgis...Anyway, thank you very much for your help!
Jan
27
accepted clip linestring by length
Jan
27
comment clip linestring by length
Right, your suggestion works fine but it seems that postgis has problems converting some specific multilinestrings into linestrings which is necessary before calling the st_line_substring function. Is there a way to come around this postgis issue?
Jan
26
comment clip linestring by length
thx, i ll give it a try!
Jan
26
asked clip linestring by length
Jan
16
accepted Is there a straightforward way to get the source/target point geometry of an edge?
Jan
16
asked Is there a straightforward way to get the source/target point geometry of an edge?
Jan
16
comment line segments using points
hi, i am now usign 1.5 but i will definatelly install 2.0 once it gets a bit more stable. Anyway, what I did to solve this issue was to get the npoint count and create a dictionary in my code with vertex id as key and point geom as value. I could then use postgis 1.3 functions to come around my problem. Of course when 2.0 is installed, i will be able to greatly optimise my code :)
Jan
10
comment How does pgRouting shortest_path work?
Yes, I agree this is a straightforward answer to the title. My issue has to do with how the algorithm is identifying the verticies so that the dijkstra algorithm can work.
Jan
10
comment How does pgRouting shortest_path work?
Yes, I just saw your update. I will try and work with smaller line segments. Thank you very much for your input.
Jan
10
accepted How does pgRouting shortest_path work?
Jan
10
awarded  Commentator
Jan
10
comment How does pgRouting shortest_path work?
I can tell you what does not work for sure, if I digitise 10 parallel lines and then intersect all of them with one line, these intersections are not identified when I call assign_vertex_id. Now, if I digitise a line and then start a new line snaped at the end of the previous, this vertex is identified. But of course I want the first technique to work as well..So this probably means I have to digitise smaller lines and connect them using the end of the previous line as the beginning of the next? That would create lots of unnecessary data...but would work
Jan
10
comment How does pgRouting shortest_path work?
Right, I ll try a smaller set and see how it goes. Lets hope its a snaping problem! Thanks for your time!
Jan
10
comment How does pgRouting shortest_path work?
Sure, I tested what you suggested and it works with specific examples but not with others, so I guess I have wrongly connected vertices. So in my db there are sources and targets like this (gid:1,s:1,t:2),(gid:2,s:3,t:4)...In this case though, gid:1 is intersecting gid:2 but I guess a vertex is not properly created, eitherwise it would be picking it up..
Jan
10
comment How does pgRouting shortest_path work?
Hmm, ok I am starting understanding how pgRouting works. So I can see some connections in my db. Some connections do exist but some others do not. But when I look at my lines, there is a path that can be followed to reach whichever I want through the intersections...