Plot of the righting arm (GZ) against angle of heel — the cornerstone of intact-stability assessment.
Regulatory detail & full definition
Required by IS Code 2008 to satisfy several criteria: area under the curve from 0 to 30 deg >= 0.055 m·rad; 0 to 40 deg >= 0.090 m·rad; GZ at >= 30 deg >= 0.20 m; angle of maximum GZ >= 25 deg; initial GM >= 0.15 m. Computed by a stability programme (NAPA, GHS) for each load condition; the master signs off.