Stop thinking lines and start thinking endpoints. If you convert your lines into a set of start/end points then group on x/y you'll end up an aggregation which defines your sets of road intersections.
If you want until Monday, I bet Kevin or Regina will drop full SQL into your lap. I'm too lazy (stupid). P. 2008/12/13 Andrew Ross <[email protected]>: > > 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 > > > > > > ________________________________ > > _______________________________________________ > postgis-users mailing list > [email protected] > http://postgis.refractions.net/mailman/listinfo/postgis-users > > _______________________________________________ postgis-users mailing list [email protected] http://postgis.refractions.net/mailman/listinfo/postgis-users
