GNSS Markets and Applications - Understanding GPS: Principles and Applications - page 644

Fisheries management is a worldwide mandate requiring swift action by govern-
ments when a sea boundary is intruded upon. Dwindling fish stocks have prompted
the establishment of strict guidelines for fishermen and the closure of entire grounds.
The situation is also making countries that share sea boundaries more and more sen-
sitive to foreign fishing in their waters. These tensions engender the need for accu-
rate position determination and recording to prove or disprove a boundary
violation. Many of the 40,000 North American-registered fishing vessels, and those
in most other countries, are subject to mandatory ADS. Even where not mandated,
the 45,000 vessels that fish near international boundaries find it prudent to carry
such gear for their own protection against false accusations.
GPS can aid in the berthing and docking of large vessels, by means of position,
attitude, and heading reference systems. These installations use multiple antennas
aboard the vessel to determine an accurate representation of the ship's orientation.
Combined with appropriate reference cartography, this can be an immense aid in the
handling of large vessels in close quarters. The more than 80,000 seagoing merchant
vessels worldwide are candidates for this type of system. There is a market for
extremely accurate positioning for seismic survey and oil exploration activities, as
well as in dredging, buoy laying, and maintenance. There are about 2,500 dredges and
300 buoy tenders in operation around the world. Dredge operators are paid based on
the amount of material they remove from a harbor or shipping channel, so accurate
measurement of position can optimize the operation, reducing cost and wasted effort.
The availability of GPS and accurate DGPS has proven a boon to the develop-
ment of precise seismic maps and location of drill sites with respect to identified geo-
logic structure, especially in the offshore case, where exploration teams have paid
significant revenue per day for accurate satellite positioning services. The availabil-
ity of such accurate systems for navigation has enabled much resurveying of pub-
lished marine chart information. A good portion of the data currently represented
on marine charts are more than 50 years old, and hydrographic services are involved
in the production of digital databases to an agreed-upon international format
(DX90). This information is being used in a navigational aid known as an Electronic
Chart Display and Information System (ECDIS). A typical ECDIS can cost nearly
$100,000 per installation and provide almost autonomous operation of the vessel.
Simpler ECDIS installations costing from $4,000 to $10,000 are used primarily as
aids to situational awareness in conjunction with radar and visual references. A
third class of marine charting device is becoming very popular, due to very low unit
cost. Navigators with simple built-in or disc-updatable databases allow a vector
map of a selected area to be drawn on a screen. These systems are excellent for pro-
viding a degree of situational awareness to a recreational boater, but in general are
not certifiable for use on commercial vessels.
The rise of worldwide terrorism has spurred the development of means of track-
ing of large container ships as they ply the seas. GPS plays an important role in these
kinds of systems, which also rely on satellite communications and electronic
tagging.
Marine use of GPS has been widely accepted, and differential services are well
established. Recreational vessels make good use of basic GPS for navigation, and the
early acceptance of differential GPS bodes well for the health of that sector. The
huge number of vessels and the value of GPS in marine navigation, fishing, and