Originally Posted by hoolie
... but if you keep to what it directs you will follow a perfectly straight track to the waypoint....
but then you use an active route, don't you ?
In this case of course, the GPS has a wp1 where you come from and a wp2 where you go to. With this information, the GPS "knows" when and how far you're off the direct line ...
That's the same calculation than used in the "highway" display.
But if you don't
use a route, and just "Goto" to a waypoint (that's what I normally do, as I'm lazy), it's simply pointing towards the waypoint.
HappySeagull and Jman are talking about this too (I hope
What I was thinking about is a simple "Goto" (with no route active), but overlay the arrow pointing towards the wp with drift information, which is (may be) available in O
as "ownship Heading".
In this scenario, you may be at any position, off route or not, the program simply reads your COG + the drift (= difference from COG to ownship heading) and constantly calculates both against the wp.
The arrow will point not directly to wp (as it would without drift) but by some degrees (drift) to either side ...
I sailed a narrow channel this year in Greece
(entrance to Preveza), with about 1.5 knots of sideways current. I had only the inner end set as wp and activated in the GPS with a simple Goto.
Although steering/pointing the GPS arrow to the wp, we drifted out of the buoys. (this would not have happend with a route, but it was force 7 winds and a big wave, and I had other things to do in my 31footer than programming routes ...
In the end I simply kept my COG indicator in O
directly on wp, meaning that the Heading indicator went off by some 10 Degrees.
But this angle would actually be compensation for the drift ...