| As other have explained, it's called set and drift or the speed (set)
and direction (drift) of the current. Also, if you are sailing, you
need to add in leeway or the force of the wind pushing you off course. The way to avoid "doglegging" is called Dead Reckoning. What you do
is obtain a tide table for the area you are sailing in, a chart and do
a few simple calculations to determine an EP (Estimated Position)
(time/speed/distance). Then, once underway, you sail/cruise for the
time noted on the EP and take some position fixes to determine how far
off you are from your EP. That difference in position from EP to
where you are (DR) is your actual set and drift and you can do some
calculations from there. How you correct for set and drift is to adjust your steering such that
you compensate for them by steering into them a certain number of
degrees to obtain a straight line course. Here's a good article on the subject: http://tinyurl.com/dj7h5 And another: http://pollux.nss.nima.mil/NAV_PUBS/APN/Chapt-07.pdf Most high end GPS systems have a set/drift/leeway function built in -
you set your course and the system does the calculations
automatically. Look at your manual to see how you set it up. It is a good idea to learn how to do it manually though - you never
know when that 276C craps out and you are out of luck. :>) Later, Tom |
