Hm, I hadn't considered the buffer idea - that may work pretty well
actually. The trick is to detect the presence of two ways to begin
with - I can see if there are multiple OSM IDs present, but they may
represent two ways placed end-to-end rather than side-by-side. I'll
see what can be done with a buffer, on an intersection or maybe even a
whole line segment.
-mike.
On May 17, 2009, at 11:51 PM, Guillaume Sueur wrote:
Hi,
If I understand your problem correctly, you want to get an ordered
list
of single intersections along a street. IMO you should first get the
list of all intersections, with their order, x,y, to_street and
from_street items. Then, apply a filter which could work either way :
- delete consecutive intersections involving the same streets
- delete identical intersections within a buffer
or maybe even both ways together.
Hope that helps
Regards,
Guillaume
Michal Migurski a écrit :
Hi,
This is a geometry question.
I'm working on a personal project using OpenStreetMap data that
requires
a cross street index, that is, an ordered list of every intersection
along a street. I have it working fairly well, but I'm running into a
wall with dual carriageways. Here's an example from Oakland:
http://www.openstreetmap.org/?lat=37.80892&lon=-122.28339&zoom=17&layers=B000FTF
14th Street crosses Adeline, Chestnut, Linden, Filbert, Myrtle, and
Market, but it does so twice and in two different directions. I've
gotten to a point where I'm able to extract a bundle of linestrings
that
represent a length of road between two major intersections, e.g. 14
St
between Myrtle and Market, but I'm having difficulty detecting and
correcting the potential presence of two overlapping carriageways.
I'm
hoping to have something that can deal with regular single-
carriageway
streets, this example of 14th St. in Oakland, places where a single
carriageway splits into two (e.g. to the west, where 14th crosses
Kirkham), and so on.
I'm working in Python, with PostGIS and Shapely.
I *think* what I'm aiming for is a near-parallel line detector, so
I'm
experimenting with normalizing road orientation to zero and
projecting
onto a straight line. It's getting squirrelly and I'm hoping
someone can
help point to an existing approach to this problem.
I'm open to the idea that there may be some manual intervention
needed.
-mike.
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