Viewshed: what can I see from here

Click a spot and see everything visible from it: the ground within the radius you choose that a person, a window or an antenna at that height can see. Hills and ridges block the view; the Earth's curvature is taken into account.

How does a viewshed work?

From the point you click, at the height you set above the ground, a line is traced to every cell of the terrain within the radius. A cell is visible when no ground between rises above that line. Visible ground is shaded green, hidden ground red.

Does it include buildings and trees?

No. It uses bare-earth terrain, so forests and buildings, which often block the view in practice, are not included. Read it as the most you could see.

What about the sea?

The sea counts at its surface, so it hides what lies beyond the horizon, as it does from a beach, a ship or a lighthouse. Sea is told from land by OpenStreetMap's coastline: land below sea level, such as a polder or Death Valley, stays land, and lakes keep their own level. Coastline © OpenStreetMap contributors.

What height should I use?

About 1.7 m for a person standing, 5–10 m for a second-floor window or a mast, the tower's height for an antenna. Set the target height to see where something of that height, like a wind turbine, would be visible.

How far can I see?

Up to 25 km here. The Earth's curvature and normal refraction are taken into account, so distant low ground drops out of view. 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.

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