Sounds like you want a "graph" based on the road network topology like
what is used in pgRouting. Then given the graph do a depth first
traversal of the topology, labeling the edges as you go.
If you build the graph topology (not the postgis topology), the you can
probably write a recursive query to do the traversal and labeling. I
think I would probably write a pgsql function(s) to traverse the graph
and label the edges.
Unfortunately, pgRouting does not have depth first search function built
into it, hence the need to code one in pgsql.
-Steve
On 7/12/2016 5:16 PM, Dan Jacobson wrote:
I want to go down the (all unnamed) roads in my future mountain
community assigning house numbers every 50 meters.
50-100 170-200
/ /
1 / 107 147 / 213
+-+---+---+-+----+--240--main-road--
2 48 \ 168
\
120-140
I stay on my main road, but whenever encountering a fork, first go down it.
"Depth first pre-order ordered labeled rooted binary tree traversal but with central
path"?
http://math.stackexchange.com/questions/1856814/binary-tree-traversal-with-fixed-final-node
OK for PostGIS, given a few linestrings, I suppose I first (somehow)
connect them to form a network, then ride my virtual car down it. And
whenever my odometer reaches another 50m, make a mark on the centerline.
(Assume a strict binary tree (mountain roads with no 4-way junctions))
At each road junction I first choose a side road, and if already on a
side road, first choose the left road, before choosing the right road.
When backtracking turn off my odometer, until finally back on to my main
road.
Holy smokes, sounds tough. Can I do this with PostGIS or should I go
back to GRASS or what?
(I am thinking instead of using ST_OffsetCurve (previous project, thanks
Sandro) to put odd on the left even on the right, down the centerline
I'll just put odd numbers at 25, 75m, padded "1 ", and even at 50, 100m
reverse padded " 2".) These points and their labels are what I want for output.
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