The GPX Activity Heatmap builds a personal heat map of everywhere you’ve travelled from your own GPX files — no Strava subscription, no upload, no account. Drop in a season of runs or rides and instantly see which routes you favour, all rendered privately in your browser.
How it works
The tool parses each GPX file’s XML and collects every coordinate from trkpt,
rtept, and wpt elements. Those latitude/longitude pairs are then turned into
a heat map in three stages:
- Projection. Each point is projected with Web Mercator, which
linearises latitude using
y = ln(tan(π/4 + lat/2)). This is the same projection web maps use, so your tracks keep correct shape and proportion regardless of where on Earth they are. - Density binning. Projected points are scaled to fit the canvas and counted into a pixel grid, so places you’ve crossed many times accumulate higher values.
- Blur and colour. A separable box blur (applied twice to approximate a Gaussian) spreads each point into a soft glow, intensity is log-scaled so even single-pass trails stay visible, and the value is mapped onto a blue → cyan → green → yellow → red ramp.
Reading the map
Cool blue areas are routes you’ve travelled once or twice. As overlap builds — your commute, a favourite loop, the streets near home — the colour warms through green and yellow to red at the busiest junctions. Loading more files makes the contrast sharper, since the colour scale adapts to the densest point in your whole dataset.
Notes and privacy
Because there are no background tiles, this is an abstract density view rather than a street map — but it is enough to recognise your regular routes and hotspots at a glance. Most importantly, your GPS data never leaves the browser: there are no servers, no tiles fetched, and no account, so you can safely visualise routes that reveal your home or workplace.