Lightning protection geometry aid

Rolling Sphere Calculator

150 ft rolling-sphere rooftop detail using roof-relative elevations, spacing and target height.

Setup

Current geometry

Adjust values, then roll.

Rooftop detail

H1 and H2 raise or lower the buildings. Air terminals stay fixed-size; 0 ft is the shared roof reference.

Height 112 ft Height 28 ft TARGET6 ftNEEDS PROTECTION 150 ft RADIUS 30 ft BETWEEN TERMINALSCONTACT
Roof-relative geometry: H1 = 0 ft and H2 = 0 ft place both roofs at the same reference elevation. Target height is measured above that reference roof. Target indication: after the roll, an exposed target turns red and is marked “Needs Protection.” This is a geometry/visualization aid; final design should be verified against the applicable NFPA 780 requirements and actual structure geometry.