Pre-planning your course requires setting out each anticipated leg of your journey on a chart before leaving. It is difficult to pick up planning a course mid-journey unless you know exactly where you are at the time you want to start looking ahead, so deciding to do this after all your electronics are gone is impossible unless you happen to know your exact position when they all died and you start immediately before drifting. YOU MUST KNOW WHERE YOU ARE TO DETERMINE HOW TO GET TO YOUR NEXT POINT. This sounds like common sense but at the time of crisis, common sense sometimes goes away.
How To Plan The Legs Of Your Journey Using Paper Charts
The first step is to lay out your chart and determine the course points for your trip. Lay out your chart and mark the approximate location of navigation points you want to make during your trip. The number is up to you and how much work you want to perform while navigating.
Next step is to draw lines between your course points using the straight edge on your parallel rulers.
Once the course lines are drawn, you need to determine the length in nautical miles between each intended navigation point. Use your dividers and the scale on your chart to measure distance, recording the distance next to each line.
Once distance is recorded, you need to determine the magnetic bearing of each line any time you have a change of course direction, indicating a need to adjust your heading along your course line.
You accomplish this by using your parallel rulers. Line up the straight edge to match the direction of travel along the course line.
Then carefully “walk” the rulers to the closest compass rose on the chart, making certain to maintain the straight edge in line with the intended direction of travel.
Read the magnetic bearing of the line where the parallel ruler crosses the compass rose. Use the heading indicated on the inner circle of the compass rose, which is magnetic (as opposed to “true” on the outer circle of the compass rose). Write this bearing on the chart next to the corresponding line and repeat this process for each course line.
Once your course is all planned, this chart will provide you with the initial magnetic compass bearing you will head for each leg of the journey. It will give you the distance you travel between each leg, so you can use our basic formulas once you know your speed to calculate estimated arrival time at each navigation point on the chart, and when a direction change is required.
When traveling on your voyage, you must remember to determine any current drift and wind impact and adjust your heading accordingly to compensate for each. Those discussions are found on the Dead Reckoning Discussion Pages.
Remember, your course over the ground (COG) will differ from your heading anytime the wind or current or both are not traveling in exactly the same direction or exact opposite direction you are. If they are traveling the exactly with or against you, they still impact actual speed, and so must be factored accordingly.
COG is easier to figure if you have sight of land or a stationary landmark ahead of your course. It’s also what you see if looking at a GPS screen providing your actual track.
When dead reckoning, you must account for tide, currents, and wind drift effect on off-course influence. For safety, you must know the impact tide and current has on every portion of your intended track.
Regardless of using electronic means or if dead reckoning; tides and current directly influence many ocean inlets and create very dangerous crossings at flood and/or ebb tides depending on the current impact and strength of tidal changes at the opening which quickly overpower any boat lacking sufficient engine capability for the situation created.