Calibrated horizon-dip method

Measure Earth from one photograph.

Upload a clear sea horizon. The tool finds the line and reads useful photo metadata; you answer the remaining questions in plain language.

Calculated resultR = — km

Attach a clear sea-horizon photo

No known Earth-radius value is used as an input.

01 / Image analysis

Visible horizon

Attach a horizon photographUse an uncropped photo with a clear, unobstructed sea horizon.

02 / Three answers

Complete the measurement

0/3 ready

How high was the camera above the sea?

metres

On a beach, use camera height above the water. On a cliff or balcony, use camera elevation above sea level.What lens does the photo information show?

mm eq.

Look for “35 mm equivalent” in photo details. This value could not be read automatically.

Was the camera level when the photo was taken?

“Assume level” is valid only when level was verified while taking the photo. A small unnoticed tilt can turn the answer into kilometres instead of thousands of kilometres. Positive tilt points upward; negative points downward.

Horizon extracted from the photo
Camera height supplied
Lens calibrated
Camera level answered

Advanced precision and refraction

Optional. Add known measurement precision to produce a more honest radius range.

Height ±

Field of view ±

Tilt ±

Horizon ±

Refraction coefficient

The result is computed from your height and the angular dip between true horizontal and the detected horizon. It is never replaced with the accepted Earth radius. A broad Earth-scale sanity check rejects broken calibration instead of presenting it as Earth's radius.