Zezo forum:

Post by GeGaX | 2018-01-19 | 08:59:56

Hi Cvetan;),
I searched but I did not find ...
Can you tell me what is the angle of scanning of the router as well as the pitch of the angle (5 �?) ?
Thanks

11 Comments

Post by zezo | 2018-01-19 | 12:51:15

The total scanned sector is usually +/- 120 degrees from the destination (and from subsequent boat positions)

I increase it when the race requires, usually to 150, sometimes to 180 for a while (like the start of the last VOR leg, but it slows things down.

The increment is 5 degrees, plus the calculated optimum VMG points. But the optimums are flat sometimes, like a 4-degree range downwind, and there is a unusual peak in the VOR polars at TWA 129, so you should also check the polars too.

The router also misses the VMG optimums sometimes. It may be the correct thing to do in shifting wind, or a result of error/noise in the calculations. The green track line helps you check if the optimum will give the same result.

Post by GeGaX | 2018-01-19 | 20:02:54

Ok thanks for the info ;)
Would you agree to put that on the router interface ?
Which would allow us to play on the sweep angle as well as the pitch ...

Post by zezo | 2018-01-19 | 20:06:57

That's a good point because the isochrones are filtered further to smaller angle.

Or maybe just show the full isochrones because there is also a sector filter at each step and point, and that can't be visualized.

Post by GeGaX | 2018-01-19 | 21:26:18

The interest of being able to modify the angle is a better road: Ecuador / Doldrums / Saint Helena / Cape of Good Hope for example
And for the pitch, the louvage less pronounced is faster
( to have for gybe penalty ...)

Post by zezo | 2018-01-19 | 21:43:49

Narrowing the angle does not work with strategy. The router should be able to tack upwind/downwind for a while.

The logic behind the 120 degree angle is that the optimums are roughly 40 degree off axis, and with a side wind you should still be able to sail the opposite tack.

Post by GeGaX | 2018-01-19 | 21:59:10

I agree but 120 � flange also other possible routes to longer term I think, no?
If you are under the doldrums and you want to reach the Cape of Good Hope, he will not check the highway that is usually near Brazil
120 � is enough when the weather system is in the same direction as the great circle road I think, I can be wrong

Post by GeGaX | 2018-01-19 | 22:02:29

But it's an interesting reflection, we know that Zezo offers the best theoretical route it would be interesting to see what he can offer with these 2 parameters in a different value (My curiosity is driving my learning;))

Post by zezo | 2018-01-19 | 22:45:39

it's +/- 120, 240 in total. leaving only 120 degree no-go zone. That's enough to take you from Dakhla to Cape Town via FdN. Imagine a 120-degree angle both sides of the orange line.

Post by zezo | 2018-01-19 | 22:49:40

If you have any doubts move the destination 20 degrees to the left and see if the initial track changes. If it does drop me a line and I'll take care of it - I want to give everyone equal opportunity, without compromising performance.

The only time when 120 is not enough is when you have to pass around some obstacle initially. On a straight/unobscured path 120 is more than enough - I have 10 years of observations and a lot of thought to confirm it.

Post by GeGaX | 2018-01-19 | 23:04:04

We misunderstood each other;)
I was thinking about +/- 60 � x 2 = 120 �
In no case do I put your work and your skills, it's the act of "playing" with the router options that are the source of the questions
Sorry about the misunderstanding

Post by zezo | 2018-01-19 | 23:09:23

You can see when the angle is not enough. The upwind/downwind angles can't reach the optimum VMG and track looks somehow squished.

It also depends on wind direction - you have to combine obstacles AND unfavorable wind to actually see a problem.