VOR landmass configs
Post by iconPost by Stormbringer | 2018-01-02 | 19:45:39

This may be remedial, but the islands in the Bass Straight and the landmass profile of southern Australia don't seems to align between the VR interface and the chart here. I can't maintain the course prescribed here without hitting land as we gybe up the coast.

Last night my plotted course here had me gybing before reaching the Kent Islands, but that same TWA and time in VR put me well beyond them.

I'm sure it has something to do with different map projections or something, just wondering. Thnks Zezo amazing site here.


commenticon 5 Comments
Post by iconPost by zezo | 2018-01-02 | 20:55:42
Map projection does not matter. Under the hood it's all floating point numbers for latitude and longitude.

What matters is the resolution of the chart (important for small islands) and all the small differences in wind speed and directions. Half degree here, 0.1 knots there and things add up.

Even the game interface itself should be taken with a grain of salt - server uses slightly different winds and few hours sailing on fixed TWA can get you in unexpected position.

See this thread if you haven't already http://sail.zezo.org/forum.pl?tid=6195
Post by iconPost by Stormbringer | 2018-01-03 | 15:40:31
I understand the map resolution, but what would you recommend if my Zezo plotted track ends up routing me through an island in VR? If I tack/gybe early I'm off the ideal course.
Post by iconPost by zezo | 2018-01-03 | 17:22:00
It's hard to give general answer. You should stay within optimum TWA limits most of the time (maybe push a bit above sometimes, 145 instead of 141 at moderate speeds (VOR boat) is small loss and worth staying for hour or two instead of two gybes.

If it's not on the VMG point then go for the shorter distance. Or the stronger wind side. Or the side with better angle after passing the island.
Post by iconPost by Stormbringer | 2018-01-03 | 17:54:12
OK, still don't understand the reason for the discrepancy between Zezo and VR maps, but you're doing enough work already, we can't expect you to steer the boat for us as well!
Post by iconPost by zezo | 2018-01-03 | 18:12:00
The router has very coarse map - about half mile resolution, so the data is small (few megabytes) and the lookup is fast.

Every push of the Go button involves few million trigonometric calculations, polar lookups, collision lookups, gate checks and it's hard to squeeze in 2-4 seconds run time.
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