This library converts KML routes into the shapes.txt format compatible with the General Transit Feed Specification.
Associating kml coordinates to stops by euclidian distance is trivial. The reason this is an interesting problem is that routes can overlap (e.g. as the vehicle comes back down the street in the opposite direction) making the distance traveled by stop ambiguous.
This algorithm resolves the stop to a point on the route by ignoring that part of the route that has already been covered.
Naturally you'll need a GTFS directory and a KML file with the route polygons. You can find examples in the fixtures and metroshuttle_example directories.
To run the converter you'll need to have Ruby and the Geos lib installed. You can get the necessary ruby gems by running bundle in the root of the project directory.
To generate visualisations (as per the above diagram showing the looping route used for testing) you'll need R (and several packages installed: rgeos, rgdal, and ggplot2) to run the visualise.r script. This isn't necessary for the conversion itself but it has been include to aid with debugging.
The converter needs both the KML and GTFS:
converter = KMLtoGTFS.new
converter.import_kml_file('path/to/my_route.kml', route_name)
converter.import_gtfs('path/to/gtfs_dir', route_id)
Where route_name is the Name of the Placemark in the KML file and route_id is the corresponding value from the GTFS.
You can create shapes.txt i.e shaped_id, shape_pt_lat, shape_pt_lon, shape_pt_sequence and the (optional) shape_dist_traveled:
converter.csv_for_shapes
Or use txt_for_shapes if you don't want the csv headers.
The shape_dist_traveled field used in stop_times.txt is also provided.
converter.distance_traveled_by_stop
An example has been included for the Manchester's Metroshuttle along with the GTFS and KML files needed to recreate this. You can run the script as follows
$ ruby update_gtfs_with_shapes_etc.rb
This will use the contents of the metroshuttle_example/gtfs_original directory and the metroshuttle_example/kml/MetroshuttleRoutes.fixed.KML (which fixes the reversed lat/lons from the original TFGM release) to produce shapes.txt and update trips.txt and stop_times.txt in the metroshuttle_example/gtfs_update directory.
The converter currently makes the assumption that a route only involves one set of stops. In reality GTFS provides for multiple sets of stops for different trips (as defined in stop_times). The GTFS is currently simplified in a naive manner - the route is mapped to all unique stops across all trips on that route. These are arranged by sequence which means two different trips on the same route will overlap and confuse the converter.
This problems mean that the Metroshuttle 2 route in the example cannot be parsed. The arrangement of stops in the different trips on this route move in opposite directions and the converter thinks it has covered the whole distance by the second stop.
To resolve this problem the converter needs to be modified to generate shape_dist_traveled for each trip.
The converter must also be modified to account for the fact that the last stop is often the same as the first stop (currently this means the distance traveled at the last stop is mistakenly set to 0).
Parallel work is also ongoing into a conversion between arbitrary vehicle GPS locations and GTFS-RT. This hasn't been released yet.
Copyright (c) 2012 Robin Gower. Released under Affero General Public License.