Ideal-sphere geometry only—not cadastral, boundary, survey, navigation, or legal accuracy. The SVG is an equirectangular diagnostic and is not proof of geographic shape or intersection.

Radius presetSphere radiusRadius unitOutput unit

Ordered vertices: latitude,longitude lines; optional CSV header; or GeoJSON Polygon (outer ring only)

GeoJSON scope is Polygon outer ring coordinates[0] only; holes and MultiPolygon are rejected. Input order is preserved. A repeated final copy of the first physical point is recognized as explicit closure and removed only for calculation.

Per-edge diagnostics

Edge	From → to	Normalized Δlon	Central angle	Length	Antimeridian	Diagnostic

Spherical Polygon Area Calculator

Per-edge diagnostics

Method and warnings