This blog post gives an overview on how to segment streets in OSM data.

Overview

A street in OSM data is a linestring. A Linestring represents a sequence of points and line segments connecting them. Segmenting is a process of dividing a segment into multiple segments.

Need for Segmenting

Let us suppose there is a big street represented by a linestring. Let us suppose that we interested in a particular part of the street and not the whole street. In such cases we may have to segment the bigger street into small streets.

A figure explaining the above:

Some PostGIS Functions

Before we start with segmentation, let us first try to understand some basic PostGIS functions which are used in segmentation process.

ST_Split function splits geometries and returns a collection of geometries. The code below illustrates an example

SELECT ST_AsText(ST_Split(ST_GeomFromText('LINESTRING(0 0, 2 2)'), ST_GeomFromText('POINT(1 1)')));

                          st_astext                          
-------------------------------------------------------------
 GEOMETRYCOLLECTION(LINESTRING(0 0,1 1),LINESTRING(1 1,2 2))