“bearing to the waypoint,” be aware that the and attached the GPS to the autopilot. The
GPS is choosing and displaying the shortest great circle route chosen by the GPS took the
distance between your position and the way- boat aground on Sable Island off the coast
point and does not take into consideration of Nova Scotia. So, obviously, a GPS will not
obstructions or obstacles that may exist replace your eyes and ears. When navigating
between the two points. In other words, it in close quarters, it is critical to keep your
will not recognize or automatically adjust for head out of the computer screen and on the
hazards like land, reefs, shoals and so on. Be lookout for visual hazards, traffic, etc.
sure to plan waypoints and routes that will In addition to serving as a destination, a
keep you well clear of any hazards. waypoint can serve as a position to be avoid-
On the other hand, because a GPS provides ed. Hazardous spots can be entered as way-
the direct bearing to a waypoint, you can also points; the GPS will monitor your proximity
use waypoints to delineate safe passages. On and bearing to the waypoint. Most units
a chart, mark a waypoint and establish the allow the user to create “alarm zones” around
course that will take you safely to that point. waypoints, which signals the GPS receiver to
When the GPS’s bearing to the waypoint sound an audible alarm if you close in on the
equals your predetermined safe route you designated hazard.
can turn to that course, provided that you Another valuable tool on most GPS receiv-
have visually confirmed that the way is clear. ers is the cross-track error, usually abbrevi-
Steering by simply matching your course to ated as XTE or XTK. If you’ve programmed
the bearing to the waypoint can also lead you in a route to follow, the GPS will tell you how
astray, as currents and leeway may drive you far off the route you’ve strayed. Most units
out of safe water. If you simply continue to will allow you to set up an alarm if your
t
ing
adjust course, you may become unaware of cross-track error exceeds a set distance. This
your location or your actual course over the allows you to create a lane of safe travel, and
ground. If the bearing to the waypoint con- can be particularly valuable if beating up-
tinues to veer to one direction or the other, wind in a sailboat.
you’re no longer moving directly toward it.
GPS Status Information
In addition to course and speed over the
t
r
onic Char
ground, most GPS units will also display “ve-
The Coast Guard broadcasts warnings and
locity made good,” or VMG, to a waypoint.
information on GPS in their regular Marine
Elec
VMG is a measure of how quickly you’re
Information Broadcasts on VHF Channel 16
closing the distance to the mark, and can be
(switching 22A) and on medium frequency
very valuable in determining the best tack if
2182 (switching 2670). Messages are also
you’re sailing.
broadcast on NAVTEX.
ion
Review your route on a chart, looking for
Radio station WWV also broadcasts GPS
at
the nearest hazards. Establish intermediate
status reports at 14 and 15 minutes past the
ig
waypoints if necessary to stay in safe water. A
hour on 2.5, 5, 10, 15 and 20mHz. WWVH
broadcasts these reports at 43 and 44 min-
a
v
surprising number of stories circulate about
N
sailors punching in routes that took them
utes past the hour on 2.5, 5, 10 and 15mHz.
aground. One boat left New England for
For more information on WWV and WWCH
Europe, plugged in a waypoint off England
broadcasts, see page 826.
Electronic Charting
Electronic charting has advanced tremen- the early 1990s. Now the U.S. government is
dously in the last few years, and going for- developing its own official electronic charts.
ward will continue to be increasingly com- In its most basic form, an electronic chart
monplace on nearly all sizes of boats. is simply a representation of the nautical
The value of electronic charts cannot be chart on a computer screen. However, more
underestimated; they dramatically simplify sophisticated electronic charts can provide
navigation and improve safety. Numerous a navigator with the ability to automatically
private firms have been producing electronic overlay the chart with information from a
charts and electronic charting systems since GPS, radar, depth-sounder, satellite photos,
aerial photos and weather reports. Mariners
847