Topo turns a line on a map into the terrain beneath it. Pan anywhere on Earth, set a pin, set another — the chart shows every elevation along the great-circle path between your pins, as height above sea level and as height relative to your starting pin A, so descents below your origin read as negative numbers. Keep setting pins (up to 26) and the line extends leg by leg; drag any pin to reroute it. On first visit the map opens on your own ground, if your browser shares its location — nothing is stored or sent anywhere except to your own screen.
Elevations come from the Copernicus GLO-90 digital elevation model (90-meter resolution, the European Space Agency's global terrain survey), served by Open-Meteo. The line is sampled at 100 points along the true great circle, so long lines follow the curve of the planet, not the flat map. Below-sea-level terrain is real data — try the Dead Sea, 427 m under.
The profile's colors are hypsometric tints, the same convention printed atlases use: teal below the sea, greens for lowlands, tans and umbers for mountains, pale snow at altitude — and the line on the map is painted in the same tints, so map and chart share one key. 🔺 marks the line's highest point, 🔻 its lowest, 📐 its steepest pitch; distance ticks along the line match the chart's axis. Grab an endpoint to drag the line somewhere new.
Import GPX turns a recorded track into pins (simplified to 26, corners kept — elevations still read from GLO-90, not the file). The 🌊 Flood slider raises a water level across chart and map at once. Open in Relief hands the line's neighborhood to Relief, its sibling tool, as an explorable 3-D block.