Heatmaps from GPX Tracks

'Heatmaps' can be used to display multiple GPX tracks to illustrate how frequently specific routes are riden.

This page shows three different presentations of heatmaps

Tracks Overlaid on Raster Images

This technique was used to generate maps for the Exeter Bike Bus, primarily to identify roads which had not been ridden.

Routes which had been riden were shown by a series of black dots at 100 m intervals. Overlaying multiple tracks meant that frequently ridden roads showed up as a continuous black lines.

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Tracks Overlaid Separately on an Interactive Map

This simply overlays all GPX tracks on an interactive map.

A standard commercial GPS (or mobile) records locations with a quoted horizontal accuracy of around 10 metres. In reality over 30% of locations will have errors larger than this, often substantially so as a result of signal loss or other glitches.

Although GPS devices calculate locations at one-second intervals, in order to save space typically only selected points are written to a GPX file (winnowing). In the present study (using a Garmin eTrex 30) points are selected automatically to ensure that the GPX track remains reasonably close to the actual track. Thus on a long straight road the device may only record the start and end of the 'straight'

The two images below show tracks collected over a 20-year period around the A38/Kenn junction and the centre of Exeter. These clearly shows the 'spread' of tracks resulting from GPS error, and long straight segments resulting from winnowing of points in the GPS to save space.

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Tracks Consolidated to Follow Mapped Bike Routes

This technique takes each GPX track and 'matches' it using the Open Source Routing Machine (OSRM) to the nearest 'bikeable' segments (called ways) on the OSM (Open Street Map) dataset.

A count is then maintained of how many times a given segment is ridden. The segments are then displayed on the map - the width and colour of the lines indicating the number of times a segment has been ridden (in either direction).

The images below show data collected in Devon and the South-West over a 20-year period (2003-2022 inclusive).

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