How does it work? It simulates the way your vessel floats and the way it responds to an overturning force. In order to do this it uses a computerized model of the vessel complete with tanks. You input current tank and cargo loads (or those that you plan to have at some point) and the software displays the stability margin for that loading case. If the margin is positive, you're ok. If negative, your loading does not meet the standard and is considered dangerous. Below is an example of what the GLM looks like on a computer screen.