GZ Curve
Abbreviation: GZ
Plot of the righting arm (GZ) against angle of heel — the cornerstone of intact-stability assessment.
In practice
The OOW reads the GZ curve from the loading instrument before sailing in any condition with cargo on deck or partial loads. Vanishing-stability angle <60° in normal voyage condition is rejected; the loading manual lists corrective ballast and trim moves.
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.
Authoritative source: 2008 IS Code ↗
Related
Source: International Code on Intact Stability 2008 (IMO Res. MSC.267(85))
High confidence
Editorial confidence: how we grade.