The Weekend Navigator Part II Copyright 2008 Coast Guard Auxiliary Association, Inc.

Chapter 8: Underway with GPS and Paper Charts

Steps in Waypoint Navigation Select and activate the waypoint Double check that you have a pre qualified path Steer to the direction on the GPS

Steps in Waypoint Navigation Monitor your progress Be alert as you approach your destination Select and activate the next waypoint

Staying on Course Reasons why you may wander off course –Steering to avoid visible obstacles –Crosswinds –Crosscurrent –Your boat yawing in waves –Inattention at the helm

Staying on Course Recovering from off course –Make sure the path you take back is clear of obstacles How can I use a GPS to tell where I am? –Using LAT/LON coordinates –Bearing and distance to a waypoint Have physical significance because they provide the bearing and distance to your active waypoint

Staying on Course Use another waypoint for bearing and distance –Waypoints off to one side provide better greater precision and convenience

Staying on Course Effects of wind or current –Will push you away from your intended course –Can result in a hooked course or a curved path instead of an intended straight line to your waypoint –It can be dangerous to steer directly to a waypoint without checking your position first

Staying on Course Your actual track is at an angle downwind or “down current” The solution is to head upwind or “up current” proceed “crabwise” along your course line

Staying on Course The question is how much to compensate? –Stay in the center of the GPS highway and “oversteer” to return to the center line Use the steering angle in small increments to maintain your course

Staying on Course Studies have shown that graphical displays are easier to monitor than numerical displays

Staying on Course Cross-track error (XTE, XTK, or “off course”) is the distance that you are off course either to port (L) or starboard (R) –Presented in feet when close to course line –Presented in nautical miles if farther away from course line

Navigating a Route with GPS GPS navigates the beginning leg as the “active from” waypoint and the leg destination as the “active to” waypoint Selecting a route –Routes should be pre-planned in segments –Clearly label waypoints to avoid confusion –Double check, double check, double check!

Navigating a Route with GPS Following a route –Imaginary “highway route” extends to all subsequent waypoints –Your position is indicated by a symbol –A track line is also visible Entering a route at a midway point –May be done during your course

Navigating in a Region Make use of the map screen when navigating casually Set your zoom level to correspond with your speed Be sure not to “outrun” your GPS

Marking Objects Locally maintained ATONs and other objects may not be on the chart Make note of landmarks useful for position finding or checking your GPS and ranges

Keeping Track Traditionally, you maintain a plot of your progress by dead reckoning and fixes What happens if your GPS quits? Plot your GPS coordinates on your chart from time to time –In open waters, once an hour is adequate –More frequently at high speed, dangerous water, or bad weather