Friday, February 17, 2017

How to Add a Walking Time Layer to a Map

An isochrone layer shows travel times on a map. It can be used to show how long it will take to travel from one location to other locations on a map. For example it can be used to visualize how far you can walk within different periods of time from a given location.

If you want to add a walking time layer to an interactive map then you can use walkshed.js. Walkshed.js is an opensource JavaScript library for adding a simple walking times layer to an interactive map. You can view walkshed.js in action on this interactive map. If you click anywhere on the map a walking time isochrone layer is instantly added to the map, showing how far you can walk from that location in incremental periods of time.

The walking times are calculated on the client side in the browser, so the map works very quickly. Essentially walkshed.js works by analyzing the OpenStreetMap data in the map layer. It assigns friction values to the map data to work out how easy it is to walk at each location. For example water, railways and interstate highways are given a high friction score because they are very hard to walk across. Conversely a park is given a low friction score because it would be easier to walk through.

If you want more information about how walkshed.js works then this YouTube video, Walkshed.js: Measuring Walkability with Client-side Raster Processing, provides a detailed account of how walkshed.js calculates walking times in the browser.

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