SCIENCE REVIEW 1987 - Bedford Institute of Oceanography

Research
River. On this survey it is estimated that
over 100 million depth measurements were
made, of which 1.5 million were logged for
subsequent data processing!
Before the first project was completed,
the system’s capabilities were clearly
demonstrated. Several large boulders in the
dredged channel that had been missed by
conventional survey techniques were
detected by the sweep system. It has been
successfully deployed on many projects in
Nova Scotia and New Brunswick. In a
demonstration of its arctic capabilities, the
system was used to carry out a survey on
the southern coast of Ellesmere Island near
the community of Grise Fiord during the
summer of 1984. In addition, the system
was loaned to Public Works Canada along
with training and support from the CHS
for a number of their projects. They, in
turn, have recently acquired a system for
their own use.
The FCG Smith
The success of the “transportable”
system provided a catalyst for a second and
larger dedicated sweep vessel. The goal was
to acquire the most modem, efficient and
capable sweep system in the world. A
contract for the construction of the FCG
Smith was awarded to Georgetown Ship-
Fig. 5 The CSS FCG Smith.
44
yards in Prince Edward Island during
January 1984. A catamaran hull was
selected to provide a high degree of
stability and manoeuverability. The principle
particulars of the vessel are:
Overall length 34.8 metres
Beam 14 metres
Draft 2.1 metres
Gross Tonnage 429.7 tonnes
Speed 10.5 knots
Shaft Horsepower 2x400HP
Swath Coverage 42 metres
Crew 11
The FCG Smith is the largest catamaran
ever built in Canada.
The vessel (Figure 5) is named after
Frank Clifford Goulding Smith who served
as the Dominion Hydrographer of the
Canadian Hydrographic Service from 1952
to 1957. A 33-channel Navitronic sweep
system has been installed on the vessel. The
sweep system’s computer is also interfaced
to the auto-pilot and may be used to steer
the vessel along predetermined survey
lines. While a number of positioning
systems have been used with the vessel, the
Krupp Atlas Polarfix is utilized on most
projects because of its high inherent
accuracy.
Polarfix is a range bearing laser positioning
system. A specially designed prism
is fixed to the vessel’s mast and a shorebased
laser tracking unit measures the
range and bearing to the prism. A telemetry
link transmits the range and bearing data to
the ship and the sweep system’s computer
computes the position of the vessel and
provides this information for steering along
predetermined survey lines. Polarfix has an
operational range of 5.0 km and an accuracy
of ± 1.0 m.
A self-contained computer center on the
FCG Smith houses a MicroVax II computer
and associated peripherals for on-site
processing of data. The data processing
software has been written by Hydrographic
staff at BIO. Some 300,000 to 500,000
depth measurements are logged during a
normal survey day. A comprehensive suite
of programs allows the data processor to
create survey track and swath coverage
plots, select the critical shallow depths for
the field sheet and interactively edit any
erroneous data. The final field sheet, which
is eventually used in the production of a
nautical chart, is normally plotted at a scale
from l/1,000 to l/5,000, and will only
portray 0.5 to 2 percent of all the depth
data that were initially gathered.
Since the FCG Smith was commissioned
in 1986 the vessel has undertaken
numerous survey projects throughout the
Atlantic Provinces. During the past two
survey seasons it is estimated that the FCG
Smith has logged and processed over 50
million depth soundings from areas such as
Yarmouth, Liverpool, Halifax, Sydney,
Port-aux-Basques, Charlottetown and the
Miramichi.
With the introduction of the FCG
Smith, the “transportable” system was
transferred to the Central Region of the
CHS, Burlington, Ontario, where it is used
on a routine basis for sweeping harbour
approaches, canals, basins and dock sites.
Together, the two systems have greatly
enhanced the capability of the CHS to fulfil
its mandate of providing accuracy and upto-date
charts of Canada’s navigable
waters.
References
BURKE, R.G., “The Canadian Hydrographic Service
(Atlantic) Sweep Program. A Status Report”.
Lighthouse, Edition No. 27, April. pp. 25-30.
BURKE, R.G. and FORBES, S.R. “Vertical Acoustic
Sweep Systems: A ‘New Broom in the Closet’ for the
Canadian Hydrographic Service”. Hydro ‘84, Rockville,
M.D. pp. 50-58.