Tuesday, March 26, 2024

Mapping SpaceTime

I recently stumbled upon Time Map, an interactive map which attempts to show points of interest around a location by walking time. Enter a location into the Time Map and a venue category (eg pizza restaurants) and the map will display a series of concentric circles around your location, each of which represents a minute of walking time. 

All the nearby points of interest are overlaid on top of these circles showing you at a glance how long it will take you to walk to each location. If you click on any of the displayed venues a map is then displayed with detailed walking directions to the venue from your entered location.

Václav Volhejn has a problem with this kind of time radius map. The circles displayed actually show equal distances from a point and not equal travel times. Real world obstacles, such as buildings, rivers, and train lines mean that we can't always travel in a straight line between two points. So in reality it is going to take us different lengths of time to walk to different locations even if they are all on the same 5 minute walking time radius.

a map of Los Angeles distorting between showing distances and time.

Which is why Václav has invented Spacetime maps. Spacetime maps distort space to show travel times rather than distances. This might sound a little complicated (because it is) but you can get an idea of how the map works in the animated screenshot above, which is switching between showing distance between points to showing travel times between different locations.

Of course cartographers are used to using isochrones for visualizing time on maps. An isochrone is a line on a map that connects all the places you can get to within a certain amount of time. Because of the physical barriers to straight line travel isochrones are very rarely circles.

Václav Volhejn's YouTube video introducing his map has a neat explanation of what he is doing 'One way to think about it is we are going to bend the isochrone back into circles'. 

It is a neat explanation but unfortunately this distortion of the physical space means that Václav's Spacetime maps are not as easy to read as isochrone maps. Václav accuses iscochrones as being as 'boring af'. Which I think in a neat way brings us to the conclusion that Václav's Spacetime maps is a fun experiment. An experiment which is probably not going to replace the isochrone as the best way to visualize travel time.

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