Concave Earth Calculator

Concave sagitta vs theoretical convex drop on a 3959 mi-radius sphere

Concave Sagitta
16 ft 8 in
Arc height above chord midpoint at 10.0 mi.
s = R − √(R² − (d/2)²)
Convex Drop
66 ft 8 in
Drop below tangent at 10.0 mi on sphere radius 3959 mi.
h = R − √(R² − d²)

Scale — sagitta vs drop

Sagitta: 16 ft 8 in
Drop: 66 ft 8 in
Distance: 10.0 mi  ·  Radius: 3959 mi(Earth)  ·  1 ft per segment width
Sagitta diagram showing the distance between an arc and the center of its chord