SCIENCE REVIEW 1987 - Bedford Institute of Oceanography

BURKE, R.G., FORBES, S.R. and STIRLING, C.H. BURKE, R.G., FORBES, S.R., VARMA, H. and
“The Vertical Acoustic Sweep System. ‘An Acoustic WHITE, K.T “2,088,000 Depth Measurements Per
Broom’ for Hydrographers”. Proceedings Colloquium Hour - A Formidable Data Processing Challenge for
IV. Land, Sea and Space - Today’s Survey Chal- any Hydrographer”. 1987 Canadian Hydrographic
lenge. Lake Louise, Alberta, April 21 - April 25, Conference proceedings, Burlington, Ontario, Febru-
1986. pp. 77-85. ary 1987.
Electronic Chart Developments
S. T. Grant
Introduction
S.T. Grant
A nautical chart is a map that shows the
positions of islands, shallow water areas,
deep channels and the coastline and
contains a wealth of other information. It is
used by mariners to safely and efficiently
navigate their vessels. The Electronic Chart
(EC) uses the advances in computer and
video display technology of the past decade
(eg. video games) to present the information
normally found on the paper nautical
chart along with other useful information
such as ship’s course and speed and radar
on a high resolution video display located
on the ship’s bridge. It offers many
advantages over the conventional paper
chart but to achieve the full potential a
number of major technical and administrative
problems will have to be solved.
The EC is the culmination of many years
of efforts to centralise and clearly display in
real time, all the information the mariner
needs to know. In the early days, as devices
such as logs (for measuring ship’s speed),
gyro compasses, radars and electronic
positioning systems (devices that use
special radio waves to determine a ship’s
position at sea) became available they were
clustered on the bridge where they could be
seen at a glance. However, the chart always
remained as a separate item and there was
always a delay between obtaining a
position, plotting it on the chart and then
extracting the necessary information (eg.
water depth) for comparison with the
appropriate device (eg. echo sounder). This
took so long that while the mariner always
knew where he had been, he never knew
exactly where he was at that instant.
During the seventies rapid advances in
computer and video display technology
resulted in displays that showed the vessel’s
position relative to a simplified coastline.
The high resolution colour displays of the
eighties resulted in better prototype ECs
that were starting to approach the quality
of the nautical chart. Mariners who used
these few rudimentary systems were
generally impressed with the fact that for
the first time they could continuously and
in real time have a bird’s-eye-view of their
ship in relation to nearby charted features
(eg. coastlines). They also were able to see
their past ship’s track plotted in far more
detail than they could ever do manually.
Electronic Charts are only as good as the
navigation systems used to determine the
ship’s position. Using this information the
EC can accurately locate the ship’s symbol
on the display relative to charted features.
If the position is in error the symbol is in
the wrong place and the mariner may think
his vessel is safe when in fact it may be in
danger of running aground. This problem
will be solved to a large extent when the
new U.S. Satellite positioning system -
Navstar Global Positioning System (GPS)
- becomes generally available in the early
KERR, A.J., ADAMS, A.L. and BURKE, R.G. “CSS
FCG Smith Hydrographic Acoustic Sweep Vessel”.
International Hydrographic Review, Volume 64,
No. 2, July 1987. pp. 7-19.
ROSS, W.M. “Sweep System from Start to Finish”.
1987 Canadian Hydrographic Conference Proceedings.
Burlington, Ontario, February 1987.
nineties. It will provide world-wide continuous
positioning accurate to between 10
and 100 metres. The mariner has never had
this capability in the past and an EC will be
necessary to exploit its full potential.
However, even with GPS, there will be
times when the mariner will want to check
the accuracy of his ship’s position. ECs are
therefore being designed that combine the
chart display with the radar image. If the
radar image matches the charted shore line
the mariner will have immediate conlirmation
of the accuracy of his ship’s position.
The fully developed EC will have a
profound impact on marine navigation in
Canada and throughout the world. It will
give seafarers the full benefit of the
revolutionary positioning capabilities of
GPS. Indeed, the capabilities of GPS
cannot be fully exploited without a continuously
updated automatic display. The EC
will be particularly important in congested
harbors, in low visibility such as fog and
snow or when ice has removed the buoys
and markers. It will help large tankers to
berth safely, will enable ferries to remain
on schedule and will greatly simplify
navigation for the growing number of
pleasure boaters.
The EC will have a special role in the
Arctic. By superimposing the ship’s radar
image of the ice edge on a chart background,
it will enable the mariner to see
readily where the ice is blocking a navigation
channel and to distinguish ice-edge
echoes from coastline echoes. In addition,
the EC provides a cost-effective means of
supplying chart data to the limited number
of Arctic users without having to actually
print the paper chart.
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