How does one measure GT

I am trying to figure out the gross tonnage of the vessel I've been working on for my masters captain's license. It's an old 100 foot vessel made from a barge. It has cabin area below, the main deck, then usable area on top of the super structure. Any directions or ways to do it. The boat doesnt have any weird angles or anything, its pretty straight forward. thanks. email: whiteb6@auburn.edu

 

From CRS:




GROSS TONNAGE
The gross tonnage (GT) of a ship shall be determined
by the following formula:
GT = K1 ⋅ V
where:
V = Total volume of all enclosed spaces
of the ship in cubic metres, calculated
in accordance with the requirements
referred to in 2.9,
K1 = 0,2 + 0,02log10 V



2.9 CALCUALTION OF VOLUMES
2.9.1 All volumes included in the Calculation of
gross and net tonnages shall be measured, irrespective of the
fitting of insulation, lining or the like, to the inner side of the
shell or structural boundary plating in ships constructed of
metal, and to the outer surface of the shell or to the inner side
of structural boundary surfaces in ships constructed of any
other material.
2.9.2 For ships which have permanent independent
cargo tanks constructed within the ship (e.g. gas tankers) the
volume of those tanks shall be calculated to the structural
boundary of such tanks irrespective of insulation which may
be fitted on the inside or outside of the tank boundary.
2.9.3 Volumes of multi-purpose vessels which have
the facility to trade with cargo hatches open or closed shall
always be measured with the hatch covers considered to be
closed.
2.9.4 The volume of weathertight steel pontoon covers
on hatchway coamings shll be included in the calculation
of the total volume (V) of the ship.
2.9.5 Volumes of tanks which are permanently located
on the upper deck provided with removable pipe connections
to the cargo system or the vent lines of the ship shall
be inculed in the total volume of the ship as well as to the
cargo space volume.
2.9.6 The volume of the livestock carriers, such as
livestock corrals and their associated spaces and passages,
situated above the existing upper deck, are included in the
total ship/s volume. Stanchions, fences and other railings are
"other means for securing cargo" (see 2.3.5) and shall be included
in cargo spaces.
2.9.7 Bulbs, fairwaters, propeller shaft bossings or
other structures shall be treated as appendages.
2.9.8 Hawse pipes, sea-valve recesses, thruster tunnels,
rudder shaft trunk, stern chutes in fishing vessels,
dredging wells and other similar spaces fitted in the ship's
hull shall be considered as spaces open to sea.
2.9.9 Enclosed spaces above the upper deck, appendages
and spaces open to the sea, not exceeding 1 m3, shall
not be measured.
2.9.10 Masts, kingposts, cranes, crane and container
support structures, which are completely inaccessible and
above the upper deck, separated on all their sides from other
enclosed spaces shall not be included in the total volume of
all enclosed spaces. Air trunks having a cross-sectional area
not exceeding 1m2 may also be excluded under the beforementioned
conditions. All mobile cranes shall be exempted.
2.9.11 Volumes shall be calculated by generally accepted
methods for the space concerned with an accuracy acceptable
to the Register.