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Why does the elevation look wrong?

Updated 2026-08-15

Terrain elevation does not come from your device. It comes from a satellite survey of the Earth's surface (SRTM). That survey recorded the topmost thing at each point on the ground. Usually that is the ground. Sometimes it is a forest canopy, a roof, or a bridge.

So a profile can show a sudden 20-metre bump where the trail runs under trees. It can show a step where the trail passes a building. The terrain data is not broken. It is describing the top of the tree.

Position error makes it worse

Elevation is looked up by position. An inaccurate position produces an inaccurate elevation. A recorded point can sit thirty metres off the trail, which is normal in a valley or under dense cover. The elevation returned then belongs to that spot on the hillside, not to the trail you walked.

What you can do

• Prefer measured elevation where you have it. A route recorded with a barometric altimeter is usually closer to the truth than a terrain lookup.
• Recompute where you do not. Use Route › Recompute Elevation from Terrain for a route drawn on the map, or one whose recorded altitude is visibly noisy. TrailRunner Mini warns first if the route carries measured elevation. Recomputing replaces every point with terrain data, good measurements included.
• Read totals as estimates. Ascent and descent are sums, so every small error accumulates. Treat them as a guide to how hard a route is, not as a survey figure. See ascent, descent and elevation for why the two numbers differ on a loop.