# How to Read Contour Lines on a Trail Map: A Beginner's Guide Contour lines explained for hikers and mountain bikers — spacing, intervals, ridges, valleys and saddles — and how to turn them on in a free online map. Updated 2026-10-26 · TrailScout blog ## Quick answer A contour line joins points of the same height. Lines close together mean steep ground, lines far apart mean gentle ground; V-shapes pointing uphill are valleys, V-shapes pointing downhill are ridges, and an hourglass shape between two summits is a saddle. In TrailScout, open Maps & terrain and tick Contour lines — they appear with height labels, every 10 to 200 m depending on the zoom. ## Key takeaways - A contour line connects points at the same height; crossing one means climbing or descending one interval. - Close lines = steep, wide gaps = gentle. - V-shapes pointing uphill are valleys; pointing downhill they are ridges. - TrailScout draws labelled contours from 10 m to 200 m intervals depending on the zoom. Contour lines are the oldest way of showing mountains on a flat map, and still one of the most precise. Once you can read them, a map tells you not only where a trail goes but what it will feel like under your wheels or boots. ## What a contour line is Imagine slicing a mountain horizontally every 20 m and drawing the edge of each slice on the map. Each line joins points at **exactly the same height**. Walk along a contour line and you stay level; cross one and you have climbed or descended one **interval**. ## The interval The **contour interval** is the height difference between neighbouring lines. In TrailScout it changes with the zoom — from 200 m when you look at a whole range down to **10 m** when you zoom in on a hillside — and the lines carry height labels so you never have to guess. > **Tip:** count the lines a trail crosses between two points and multiply by the interval: that is the height you gain or lose. ## Five shapes to recognise 1. **Close lines — steep ground.** Many lines in a short distance means a lot of height change. On a trail, expect a hard climb or a technical descent. 2. **Wide gaps — gentle ground.** Easy riding, a plateau or a valley floor. 3. **Closed rings — summits.** The smallest ring is the top. TrailScout also marks peaks with their names and heights; tap one to [learn more about the peak](blog/identify-mountain-peaks-viewpoint-panorama.html). 4. **V-shapes — valleys and ridges.** Where the V points **uphill**, it is a valley (often with a stream). Where it points **downhill**, it is a ridge or spur. 5. **Hourglass — saddles.** The low point between two summits, where trails usually cross a ridge. ## How to show contour lines in TrailScout 1. Open [TrailScout](index.html?app) and the map. 2. Press the **layers** button (**Maps & terrain**). 3. Under **Terrain**, tick **Contour lines**. Keep **Hillshade** on for a 3D feel. 4. Zoom in to see more lines and finer intervals. The contours are computed on your device from the terrain model, so they work on every base map — even satellite imagery. *Screenshot: Map layers: base maps and the terrain layers — Maps & terrain: tick Contour lines under Terrain.* ## Contours and your route - A route that runs **along** the lines stays level — a traverse. - A route that **cuts across** many lines in a short distance is steep — check its [gradient](blog/trail-gradient-percentages-explained.html). - Switchbacks appear where a trail zig-zags across close lines to keep its own gradient low. - Combine contours with [slope shading](blog/slope-map-for-mtb.html) to see at once which slopes are dangerous. ## When contours aren't enough Contours flatten the world. If you find them hard to picture, open the [3D view](blog/preview-bike-route-in-3d.html): the same terrain with imagery draped on it, trees and buildings, and your route as a ribbon. ## Frequently asked questions ### What does it mean when contour lines are close together? The ground is steep: a lot of height change in a short horizontal distance. ### How do I know if a slope goes up or down? Read the height labels on the lines, or look for peaks (rings) and streams (in the bottom of valleys). ### What is a good contour interval for hiking or biking? 10–20 m (30–60 ft) shows trail-level detail. TrailScout switches automatically as you zoom. ### Do contour lines work offline? Yes, once the terrain tiles for the area are on your device — download an offline area before you go.