Figure 3: Spatial filtering of a GTFS feed based on stop coordinates.
From: A collection of public transport network data sets for 25 cities
The city area is defined by a center point and an associated buffer radius. Only PT connections within the defined city area are included. Each line and color corresponds to a different PT trip (=one run of a PT route). When necessary, a trip is split into multiple parts so that only those parts of the trip are retained which run within the defined city area. Here, the red PT trip is split into two parts, as it temporarily exits and then re-enters the defined city area.
