On 2014-07-29 02:09:48 +0000, Bruce Hoult said:

My take on this is simple:

- FAI classes should almost always be racing ASTs.
- MATs are useful in handicapped races with a range of performance.

John Cochrane makes a point about climatic conditions sometimes making
it difficult or risky to get to a specific point. Perhaps ironically,
the old fashioned sector turnpoints can often solve that problem, at
the cost of flying some unscored extra distance. That's better than not
completing the task.

Here's a turnpoint option I've never seen proposed or discussed:

Assume you're going from turnpoint A via B to C.

You are defined to have sucessfully rounded turnpoint B when:

- current distance to B is less than N km (10 or 20 maybe), AND

- curent distance to A plus current distance to C is greater than B to
A plus B to C


The second part defines an ellipse with A and C at the focal points and
passing through B. Flying from A to any point on the boundary of the
ellipse to C is always the same distance as actually going to B.

Given a GPS this is dead easy to calculate. You could do it even with
an ancient GPS (e.g. CAI Model 10) if you can add two distances
together in your head. Given a new one, or a PDA app it's trivial.