Walking through city streets you might see information stands with maps on them. Your location is usually marked with «You are here» sign, 5-minutes walk circle around it. It is a very usable orientation tool: it helps understanding where you can get in 5 minutes.
This line is understandable but nominal. It shows a walker’s freedom of movement in several minutes’ limit roughly. First, different people have different pace (the average is 2,5 mph). Second, natural obstacles like rivers, buildings or roads won’t let a citizen walk directly. The London picture illustrates that: one can only cross the river on the bridge.
We computed the real availability zone for that spot and it turned out to be completely different. That zone (blue highlighted) actually is averaged to some extent too, because we are in fact walking on sidewalks and paths. To make it absolutely accurate, we could draw every route, which would however make the picture overloaded.
Equal Times Line
Sir Francis Galton was a gifted English researcher, geographer, anthropologist and psychologist. He contributed to a lot of fields of knowledge development, geography included.
In 1881 with help from Royal Geographical Society he published the Isochronic Passage Chart with different zones which revealed how many days would it take to travel from London to various destinations around the globe.
In Greek, «Isochrone» means ἴσο (iso = similar) + χρόνος (chronos = time). Wikipedia describes isochrone as «a line drawn on a map connecting points at which something occurs or arrives at the same time» (e.g., duration of a trip). Isochrones are a good way to visualise how far can one get through a clear dimension of time. Apart from visualisation availability zones are useful for the spatial data analysis: for example, it is able to compute the coverage (how many people are living or working in a marked point’s walkable area).
For example, we could compute 5-minutes availability zones for the subway stations. Pictures below illustrate how dense are downtown subway stations in Paris and how sparse they are in Moscow.
An availability zone itself can be used for computing and analysing the object within the zone. It could be computation of 5-minutes availability for restaurants and cafes, a buildings counting or a population estimation. Complex calculations are also possible; for instance, we could count a number of parameters and compute an index of a place based on the walking availability.
We used NYC Open Data as an example. Here is visualisation of 311 noise complaints during August 2016. It turned out to be an interesting quiet area locator.
The idea of isochrones and its’ use cases was so exciting that we decided to develop an isochrone tool. Ladies and gentlemen, meet Galton:
Using Open Source Routing Machine, Turf and Concaveman open code and OpenStreetMap open data, we developed a fast and lightsome Node.js server for availability zones computing. We are already using Galton for Urbica projects analysing complicated urban data sets. The service is currently working on demo cities, but other areas can be added easily.
The project code is open and available on GitHub. We will be glad to answer any questions and receive any offers.
Urbica Design practice in information design, user interfaces and data analysis. We are focused on human experience design around cities. We will be happy to help organisations to develop processes, products, services, tools and environments with a focus based on the data & design.