Author

Topic: Numerical Dead Reckoning

David Burch

posted November 16, 2004 07:09 PM
This pdf article covers all methods of doing numerical dead reckoning (as opposed to plotting) and provides extensive practice problems headed in all directions in all quadrants. It is useful in all phases of navigation. That is, given a Lat Lon position and a course and distance run (or speed and time run) what is your new Lat and Lon. These notes explain the best way of doing this.
Numerical Dead Reckoning
Of the methods listed (not counting a programed calculator, which is of course the easiest way to do this) the simple trig solutions are the best choice for doing it "by hand.". They will give some signs as (+) and others as () for the lat and lon intervals, but it is rather confusing to set the rules right to use these.
Here is a suggestion on how to figure out if you add or subtract the increments: always use positive values for lat (N or S) and course. Use regular course values 000 to 360, and then disregard the sign (+/) that you get from the equations.
Then make a small sketch of your initial position labeled with lat and lon, mark off the direction of travel, and just determine by inspection if the corrections are positive or negative. This can be just a large cross with a dot in the middle for the position.
For example, in N Lat and E Lon, headed NE you have Lat getting bigger, Lon getting bigger. Headed SW you have both getting smaller. Headed NW you have Lat getting bigger, Lon getting smaller, etc.
From: Starpath, Seattle, WA


