What is GHS?
GHS is a software system for the design and evaluation of all
types of ships and floating structures. It addresses flotation,
trim, stability and strength by calculating the forces involved
using mathematical/geometrical models of the vessels.
Developed by Creative Systems, Inc. specifically for today's
computers, GHS has become widely recognized as the most
productive tool of its kind. It is continually being extended and
improved to ensure its continued leadership and excellence in
response to increasing sophistication of stability standards and
computing technology. GHS is well-proven, reliable, respected
by regulatory agencies and in constant use by major design firms
GHS is truly general-purpose. Not only does it handle ship hulls,
but also anything that floats or contains liquid - or both. It has
been used to analyze and/or design submarines, SWATHs, dry
docks, drilling platforms, 10-foot sailboats, 300-meter freighters,
floating bridges, and even a floating golf green. GHS addresses
simple and complex stability issues including intermediate stages
of flooding, spilling of cargo, and optimizing against complex
What makes GHS special?
Of the several ship stability programs available that all claim to do
most of the same calculations - some costing more than GHS and some less,
what makes GHS special and worth its price?
Part of the answer lies in the completeness of its features, some of which
are only found in high-end programs and some only in GHS; for example,
- Handling of complex stability criteria.
- True CG shifts of tank
contents both transversely and longitudinally for better realism
- Tank modes for flooding, damage, spilling, water-on-deck and
- Heeling about any axis (essential for some shapes - drilling
units for example - and where longitudinal stability is a problem).
- Wind heeling moments derived from the geometry at any heel,
trim and axis angle.
- Ease of modeling complex structures and interior spaces.
- Detailed and flexible graphics depicting conditions of flotation,
flooding and tank loading.
- Ground modeling for vessels partly or totally supported by the
- Multi-body capability for interactions between vessels.
Another part of the answer is certainly about efficiency -
especially with complex vessels where the number of load and
damage cases becomes very large. Efficiency means doing a job
accurately, correctly and on schedule. Computers naturally do
things accurately, but whether a job is done correctly still
depends on the person who prepares the inputs for the computer -
and people tend to make mistakes. GHS helps to reduce a
common source of errors with its macro commands that reduce
repetition within the input data. And when mistakes have to be
corrected, it takes little extra effort to rerun even a long report.
A large part of why GHS is special has to do with its modern
approach which goes well beyond traditional methods. The
difference this makes is not so noticeable in its list of features.
But once you discover the direct, simulation-oriented approach
that GHS encourages, you will never want to see another cross
curve. (If someone insists on seeing cross curves, you can still
get them from GHS.)
In addition there is something in the "specialness" of GHS that is
not so easy to describe. One shipyard architect said, "GHS is my
right hand". An executive in a prominent design firm declared,
"GHS is our life's blood". After using GHS for about three
years, a well-known naval architect wrote, "GHS is absolutely
stupendous in its completeness, versatility, and its accuracy".
After using GHS in a research project, the project director wrote
Creative Systems a note saying, "I figure GHS saved us about
two years of work".
The GHS system is organized by function. There is a main
program, which handles all of the usual stability computations,
both intact and damaged. From there it branches out to several
modules that perform special functions. Some of these modules
are optional, making it possible to acquire only those functions
that are necessary.
The essential modules that come with the main program are,
- SE: Section Editor -
a specialized, interactive, solid modeler
that creates, modifies and displays geometrical models of any vessel.
PM: Part Maker
- an efficient parametric solid modeler best for createing tanks
MC: Model Converter
- converts models from other formats, including
SHCP, HEC, DXF, OFE, IDF, PIAS and SEASAFE.
The optional modules are,
The Main Program
You can do the ordinary things so easily with GHS that first-time users
believe it's a simple program. But when they're still discovering features
after a year or longer, they tend to have a different opinion.
The hydrostatic approach to ship stability is essentially a simple
matter of balancing idealized weight and buoyancy forces, but it
can become surprisingly complicated when the effects of liquid in
tanks and flooding compartments are considered. GHS does not
ignore these complexities; rather it brings them to light and helps
you think them through.
When you approach a stability analysis you have to make some
decisions about how much detail there should be. You build a
geometrical model of the vessel with the appropriate degree of
detail. Then you run GHS with the model to simulate the
vessel's ability to withstand heeling moments in various
conditions - to an appropriate degree of detail. Preliminary
designs can be modeled with less detail so that they can be
quickly cycled through modification phases. Final designs will
have more detail.
Damage stability is straightforward with GHS; what happens with
loaded or empty tanks with and without damage is all taken care
of automatically. True CG shifts in tanks are the norm but the
traditional, less-accurate, free surface adjustments are also
Heeling moments from the wind plane and other sources are
available, as are several kinds of waves. GHS has few
restrictions - heel and trim are unlimited (great for salvage work).
You can change the heeling axis - heel on a diagonal or even do a
fore-and-aft righting arm curve.
Stability criteria are not cast in concrete. You can choose your
own limits and roll your own criteria. Tell GHS your criterion
and it will find the maximum VCG - even with damage, wind or
wave, or all three together.
No description of this program would be complete without
further mention of the macro facility. Being command-oriented
(vs. menu-oriented, although menus can be used), GHS is
actually a language in which you express the design of the report
you want to create - using the terms of your own building blocks,
which are called "macro commands". It's the lever with which
you can move a world of data.
Pictures in a printed report are helpful. The GHS report
generator takes the entire output stream, inserts the graphics, and
puts the report out on the printer - all automatically. This
operation is almost invisible because the program makes all of its
decisions automatically. The only decision you have to make is
whether you want graphs in your report. If you do, then the
report generator does the job with no questions asked. The report
generating facility in GHS is actually a complex piece of
software, in spite of its apparent simplicity; and a close
examination of the quality of output it produces proves the point.
GHS produces the following kinds of graphs:
- Hydrostatic Properties
- Maximum VCG Curves
- Curves of Form
- Longitudinal Shear, bending, deflection Curves
- Torque Curves of Hull Twisting
- Sectional Area Curves
- GM vs. Tank Loading Curves
- Cross Curves of Stability
- Tank Soundings and Characteristics
- Righting Arm and Area Curves
- User-defined graphs
GHS provides facilities for its own extension and expansion. It
gives you the ability to create new features and procedures. This
extensibility is of five major kinds:
1) Macro Commands. A macro command is a new command
which you design yourself. The concept is that you can
encapsulate your own procedures so that they become part of
your "customized GHS". This is an extremely powerful and
2) Menu Systems. You can design and create various menu-
driven "applications" within GHS. A MENU command is
provided which, together with macro commands, allows you to
create programs for specific applications which can then be used
by someone with little or no knowledge of GHS.
3) Templates. Similar to menus but more powerful, templates
give you the ability to construct simple or complex dialog boxes.
These can be strung together to form "wizards" that guide the
user through a complex process.
4) Programming Interface. Virtually any conceivable feature or
calculation can be added to GHS with this facility. It gives you
access to the underlying data and "hydrostatics engine" for use
within another programming environment.
5) File Interfaces. Several kinds of "industry-standard" data files
are recognized by GHS. This facilitates communication between
GHS and other programs so that you can assemble a system of
software extending into areas not covered by GHS.
Extensibility means that you are not locked into one way of doing
things. It also increases your options for enhancing and
developing GHS to meet specific requirements.
Copyright © 1997, Creative Systems, Inc.
Creative Systems, Inc.