I'm a bit baffled by those who say you need nothing more than
GPS.
Is GPS accurate? Of course it is. But make sure the GPS is
set to the earth model the chart is. Oh, and make sure you
never transpose numbers when entering waypoint data. One
more small item...check the route to make sure there are no
rocks/reefs in the way..the GPS will cheerfully run you aground.
But you've already thought of those factors.
Are DR nav methods, charts, hand bearings, etc. less accruate
than GPS? Of course they are.
Should one rely ONLY on GPS and chart plotters?
If the answer is "yes", then that inplies you believe the electronics
will never fail. And the IRS will never audit you..right?
Is there something *wrong* with suggesting/teaching mulitple methods
of navigation? I don't think GPS/radar have feelings...it won't mind
if you confirm position by other means.
Since I'm in a cranky mood, I'll tell you that the biggest risk to a boat
is not deploying the Mark One Eyeball in close waters.
For example, I've told students
over and over again to do something as simple as looking behind
them once in awhile when in the islands. But no, they look ahead for
the waypoint coming up. Imagine their surprise when that big ferry or
freighter toots it's horn a 1/4 mile aft. Happens a lot in these waters.
Norm B