Tracking Flush Tracker or Why Is It Flowing Uphill?

Flush Tracker is an interesting map-based visualisation of a slightly taboo, and therefore amusing, subject. It’s based on Google Maps, and allows you to enter a postcode and elapsed time, and then “track” a toilet flush apparently move through the sewerage network, a blue line gradually extending along twists and turns, to the local treatment works. You can also view existing tracks, which generally appear to have just started their journey from “famous” places, such as 10 Downing Street, Buckingham Palace etc.

The tracks are intriguing, they often appear to be close to the road network, but not exactly on it, with a kink every few hundred metres, suggesting somehow the map is somehow aware of a real pipe network – information which has been traditionally locked away in the GIS databases of the various water companies – not even OS MasterMap has this data, as far as I am aware.

What’s actually happening is a clever bit of Javascript trickery. When you make a request, or load in a current request, the data that comes back to the browser is a simple lat/lon of the start and the end of the “journey”. The start point is based on a Google Maps geocode of a postcode you enter. The end point is a genuine location of the water treatment works that is geographically closest to you – even if it’s uphill, i.e. almost certainly not actually the one you are connected to. For example, west London postcodes generally result in a route moving uphill to the NW, even though London’s treatment works are located “downstream” to the east, at Beckton or Thamesmead.

The clever bit is showing the “route” as a realistic sequence of pipes rather than a straight line between the start and finish. This is achieved doing a Google Maps road routing request from the start to the finish, which sends back a list of coordinates, each corresponding to a turn or other road junction on the route. Twenty or so of these are then picked on a pseudo-random basis, and straight lines are drawn, in sequence, through the twenty turn-points and to the finish.

If you look carefully, you will see that a turn of the “pipe” route always occurs at a road junction, and that the overall route generally corresponds to the Google Maps suggested road route, with road curves and certain junctions missed out and replaced by straight lines.

So – not a sudden opening up of another network dataset by the water companies, but a nice bit of map “trickery” nonetheless.

Left: Flush Tracker route. Right: Google Maps road route.