HS vs. GHS

HS gets you hydrostatic properties of the ship.

GHS is similar, but it involves the VCG—hence the "G".

HS produces a table of hydrostatic properties for a range of drafts.
It is all about buoyancy with no reference to gravity, so it is strictly
valid at any displacement.

GHS can produce a table too, but since only one value of VCG is
used at every draft, anything in the table that depends on the VCG
is not strictly valid without being adjusted for the actual VCG.
Nevertheless, the GHS table is what is customarily considered 
hydrostatic properties, so you get a graph with it.

When the vessel is in equilibrium, a one-line GHS report is strictly valid: