Slope map: how steep is the ground

The ground shaded by how steep it is. Click any spot for its slope in degrees and percent grade, the direction it faces and its elevation. Switch to avalanche angles to see the 30° to 45° slopes where most avalanches start.

How steep is a slope in degrees and percent?

Percent grade is the rise over the run: a 10% grade climbs 10 m every 100 m and is about 5.7°. 45° is a 100% grade. Click the map to see both for any spot.

What are avalanche angles?

Most slab avalanches start on slopes between 30° and 45°. The avalanche view shades only those angles. It is a planning aid, not an avalanche forecast: check your local avalanche center.

How is the slope computed?

From the elevation of each ~30 m cell and its eight neighbours (Horn's method, as in GIS software). Slopes shorter than about 30 m, like a cliff band or a road cut, are smoothed out. Elevations come from our own copy of global ~30 m terrain models (the Mapzen terrain mosaic of SRTM, USGS NED, EU-DEM and others, with ocean depths), served from our own server.

Can I find the slope of my driveway or yard?

Only roughly: at ~30 m resolution a driveway is one or two cells. For a short slope, measure on site.

Is there an app?

Not for this tool yet. The nearest is Geo Elevation, on iPhone, iPad and Mac, which draws the elevation profile of a path, with the chart tied to the map, and saves it as a document. Paid. App Store · Mac App Store