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I'm working on postgresql and I am trying to create table to generate graphs. I have a table that contains all the objects of a city (points) and another contains the city street. My goal now is to segment the street in small segments that begins and ends with two objects (points). I try with different PostgreSQL query but I can not create a table of links that restrained the source and destination of each seqments ST_pointN actually gives the first and last point in a linestring against me by I want to have all the object on a street with the order to which I may have small segments. I want to see is what pgRouting can help me segment the streets and if so how? thank you

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Please add an image to illustrate the question. Are the points located on the lines or besides them, etc. – underdark Mar 13 '13 at 10:21

Sounds like you should read about linear referencing.

ST_line_locate_point(LineString, Point) (0-1 value from start) 
ST_line_interpolate_point(linestring, location) 

using those two you get nearest point on road from your point. After that split edges to have node for those point and regenerate graph table

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