How does it work? GLM calculates the buoyancy and the weights involved using the given loads, finding drafts and tank levels. It bases its calculations on a detailed model of the ship and its tanks -- in conjunction with light ship weight distribution if longitudinal strength is being calculated.

The stability assessment can take many forms, depending on the requirements of the particular vessel:

Comparing the present VCG with precomputed curves of Maximum VCG, and displaying the Stability Margin (see the graphic below).
Calculating the righting-arm curve with the present loading, and analyzing the curve according to an applicable stability standard.
Checking the present load condition with respect to more than one stability standard, perhaps depending to a particular service mode.
Including a damage stability assessment for assumed damage at various locations on the vessel.
Performing damage stability calculations with a given flooding condition for damage control.

Depending on the type of the vessel and its needs, there are many auxiliary features that are available to the naval architect who configures the GLM for the particular vessel. Buttons around the periphery of the GLM window give access to such features.