Great circle formulae, True cource and actual heading

Dave Martindale wrote:

"John Bell" writes:


The GPS itself will indicate the amount to turn in order to reach the
correct heading. COURSE or DTK (synonyms) will change along the route as a
reflection of great circle effects. Likewise, the BEARING will also change
for great circle. While what you said is correct, a good way of staying on
course is to compare TRACK to BEARING or keep TURN to zero. This makes it
easier to find the heading that keeps the vehicle along the centerline of
the path.


I haven't heard of a GPS receiver that will tell you what heading to fly
or sail to compensate for wind or current. A GPS-only unit has no way of
knowing what your current heading is in the first place. It can tell
you how much to turn to align your heading with the desired course, but
that assumes no wind or current. In practice, you'll have to make
adjustments to that heading, while watching the cross-track error.

Dave

The III pilot does permit you to make the adjustment manually so that
you can use the GPS for guidance but it does not and cannot make this
adjustment automatically since it has no sensors to detect this.

Dale

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_ _ Dale DePriest
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