Creating Isochrones with pgrouting? [closed]

Question

I want to calculate isochrones representing the accessibility of certain locations in a city. So I have set up the pgrouting enabled database, imported the OSM-Roads and created a network. I have also calculated the "drivetime" of the road segments (time for walking, biking) and created new columns in the network table for this.

Now I have my point shapefile with the locations, which are subject to the accessability research (see screenshot).

My questions are:

1. How do I connect these location points from my point shapefile, which i imported into the database to the road network (I assume this is necessary in order to create the isochrones)?
2. Then how do I create 5min, 10min and 15min isochrones (for walking and cycling) for each of my 15 points (locations)?

I work on this for weeks now and also tried GRASS where I was at least able to connect my point shape points to the network but the outcome of v.net.iso is not what i am looking for.

A similar problem was discussed in How to connect points (bus stops), which don't lie on the lines (LINESTRING), to a network? but no solution was found. Also this popular example of finnish airports does not help me because I cannot see how the airports were "snapped" to the network from the explanation.

Could anybody help me with this?

Answer 1

In the example of Anita Graser the st_distance function is used in combination with min() to get the nearest node for every airport.if you have the id's of the nearest nodes you can loop through your table and use this id's for the pgr_drivingdistance function.

You can also have a look at the following three links where you always find a good answer from Daniel Kastl (username dkastl):

Find nearest node function

PGROuting 2 : Getting nearest node to a given point (with lat - long given)

How to get the closest point from a table in PostGIS?