[postgis-users] Finding/Categorizing Paths from A to B

[Webb Sprague]

> That is exactly what I want to do... but first I want to find a way to boil
> down all trips to 12 or so distinct paths; without having to overlay every
> trip.  But since I only have points, not streets; i have no way to say path
> #1 is different from path #2.

Write a function that returns an intersection id based on a point;
this function would have to find the closest intersection to the
input.  You need a table with intersection point geoms and
intersection ids.  The function could  be a big case statement to
start.

You might also be able to finesse this with "snap to grid" or by
rounding (look in the docs -- I would read the section on geometric
functions and see if any strike you as useful)

Then use array_accum  and group by on the path# to create lists of
intersection sequences.  Compare these however you feel like.

If you use another projection (UTM etc) the units will be in meters
and easier to interpret.

There is still a lot of work, but does that make sense?