Implement variable wind at KSFO

[tedrek]

Here's an approach for fixing #68. The basic principal is to build a wind rose for the given airport, I used data from http://www.enviroware.com/METAR/METAR_WindRoses_2014_maps.html for KSFO.

A wind direction and speed are selected with with weightings, then over a 3 hour period the wind shifts to a new direction and speed, repeat.

I increased the crosswind limit from 10 to 15 for normal and 20 to 25 for major. (Of course this can't generate cross winds over 24 knots so I'll need to fix that, I had planned to make the top tier 20-40 knots but forgot.)

Any feedback appreciated.

[zlsa]

What do you think about making the delay more like 30 minutes or so? I honestly don't see anybody playing the game for three hours and watching the wind direction move.

[tedrek]

I initially had a 60 minute delay, that seemed too fast to be realistic. It also made the wind switch fast enough that by the time an aircraft had made it's way from the center boundary to a runway that runway could be already unusable.

Looking at it now, I think there should be two different variation methods, one which slowly varies the speed and direction and one which causes quick and drastic changes. This is something which would probably benefit from some sort of configuration where the player can choose whether a drastic wind change is common (50% of games or better) or rare (5% of games or less) for example.

[glangford]

My two cents - I think this is a terrific idea in general, but I worry a bit about timing and introducing a feature like this before the baseline is more stable. With #156, #134 and #128 (and #147 should we decide to do it) does it make sense to try and reach a stable place in terms of playable arrival/departure rates first?

[tedrek]

@glangford, that's a very good point about timing. I'll leave this for now and come back to it later.

[glangford]

I am trying the enviroware link above, and getting very slow response. Here is another data candidate:

http://windhistory.com/station.html?KSFO

[erikquinn]

The ATC repository is being migrated to it's new home at https://github.com/openscope/openscope, and thus, all pull requests are being closed. If you would still like to see this merged into the simulator, please reopen the pull request at the new repo. Thank you!

Closing this PR.