Detailed Classements

During the Mini Transat I had our team Webpage open for everyone. Some saw the detailed classements I generate for our team, and asked whether I could do this for the RWC. Here you go:

http://team-yacht-treff.de/pub/cls-rwc-2.html

I will generate these classements from now for the rest of the RWC. I still have to setup an index page, but the naming of the classements should be clear.

DTF is the shortest distance to the finish line, not distance to center of finish line, so the classement should be giving a realistic outlook during the final approach to the line.

Thaks Eddie

I believe that it is very interesting

EXCELENT....
danke schön eddie...

+1

Thanks,

I made the table sortable by clicking on the header fields now, so you can see it sorted by fastest VMG or fastest Speed...

The detailed classement for the RWC Leg 3 is available at:

http://team-yacht-treff.de/pub/cls-rwc-3.html.

Vielen Dank Eddy

VERY NICE, thank you very much Brainaid.

thanks Eddie and cheers to your team.

Hi Eddie

Excuse my ignorance, but what does VMG mean in your Classement list?
I'm sure it's something obvious, but my scalp is becoming quite sore with scratching it so much.

Thanks for the very informative and interesting details.

WL

VMG means Velocity Made Good. This is calculated as follows:

VMG = (Distance to Finish at t - 1h) - (Distance to Finish at t)

where t is the time of calculation. Distance to finish is calculated as great circle distance to the finish line.

Does this answer your question?

Perfect. I could see what it was doing, but I just couldn’t put the words to the initials.
My hair has already started to grow back!!
Thanks for the information.

WL

I have just found a bug in my VMG calculation. I calculate Distance to Finish as "shortest great circle distance to the finish line". To calculate this I use the Gnomonic Projection (where all great circles are straights). For large distances this might fail, in which case I fall back to the great circle distance to the center of the finish line.

At the moment some boats show VMGs in the range of 60+ nds. This is caused by the distance calculation failure for one of the two points, and no failure for the other point. The result is comparing apples with peas.

I will fix this today, but it will take around 6 hours until I get to do the fix.

Sorry for the inconvenience.

The problem is fixed. I found some time to do this earlier

brainaid a écrit:

The problem is fixed. I found some time to do this earlier

thanks eddie for your help, on that particular point, and also for the tools you allow us to use.
join me at the bar, what do you want to drink ?
bye for now.
alain

brainaid a écrit:

VMG means Velocity Made Good. This is calculated as follows:

VMG = (Distance to Finish at t - 1h) - (Distance to Finish at t)

where t is the time of calculation. Distance to finish is calculated as great circle distance to the finish line.

Does this answer your question?

VMG = Bs x Cos(TWA) - VMG is a speed! not a range! (Bs = speed of the ship and TWA True wind angle) !
Am I wrong?
Francis

Corail Aventure a écrit:

brainaid a écrit:

VMG means Velocity Made Good. This is calculated as follows:

VMG = (Distance to Finish at t - 1h) - (Distance to Finish at t)

where t is the time of calculation. Distance to finish is calculated as great circle distance to the finish line.

Does this answer your question?

VMG = Bs x Cos(TWA) - VMG is a speed! not a range! (Bs = speed of the ship and TWA True wind angle) !
Am I wrong?
Francis

brainaid parle de la VMG vers l'arrivée. Sa VMG est une distance mais c'est aussi une vitesse car les bateaux avancent par pas d'une heure.
Donc la distance parcourue en milles en une heure = la vitesse en noeud

La distance est une distance orthodromique donc cette VMG doit aussi être la projection de la vitesse sur l'orthodromie vers l'arrivée.


brainaid is dealing with the VMG to the finish line. Its VMG is a range but also a speed because boats sail by one hour steps.
So distance in one hour in nautic miles = speed in noeuds (?)

Distance is an orthidromic distance so his VMJ is also the projection of the speed on orthodromy to finish line...

Correct ?

Ouf, déjà en français, j'ai du mal à expliquer ça. Mais en anglais...

vmg = very magnifical girl ?


where she is ?

takecare with the sirens

VMG can be dark and deep...
-----------
Francis

Yes. To all of you. For the instant moment the Cosine formula is correct. For long distances the Cosine gives the same result as my calculations.

When you get close to the finish line, the great circle bearing changes with your boat moving, so to be correct you would need to integrate the Cosine over one hour.

As we only observe the boats positions in one hour ranges, I can simplify the integration by simply calculating the "before one hour" and "now" distance to the line.

Right now (for me) going COG 090 the great circle bearing changes by 1 degree for every 12 hours of sailing (at a distance of over 5000 miles to the line). These changes will get more significant once we get closer to the line. This matter is hard to explain without pictures, but I hope I can make a little bit clear.

And yes. It is all dark and deep. But not VMG, VMG is easy. Wind is the hard part. It tricks you, it fools you into routes you don't want to follow. It is nasty, it is strong, it is scary. But you can sail without. Love it. Hate it. Swear at it. Cry. Will it change it's mind? No. Will it change your mind? Yes. Wind is the beast we cannot tame. Wind is the beast we all love so deeply. Waves is the monster wind sends to ridicule our ideas of ruling the seas.

Eddie,
Thanks to u for these very accurate explanations.
Just enjoy this funny race!
Francis

Popitoff a écrit:

Perfect. I could see what it was doing, but I just couldn’t put the words to the initials.
My hair has already started to grow back!!
Thanks for the information.

WL

VMG = Velocity Made Good
C'est la vitesse réelle projetée sur la route directe menant au point visé.
Formule de calcul : VMG = Vitesse réelle du bateau * cosinus(Cap bateau - Cap visé)
Exemple :
Le point vers lequel vous désirez aller est au relèvement 45°, votre bateau progresse au 80° à la vitesse de 12 nœuds, votre VMG est donc = 12 * cosinus(80-45) = 9.83 nœuds

une chose est certaine même si ses calculs sont faux il arrive toujours le premier!!!!!!!!!!!!!!!

The calculations are not wrong, just a different way of calculating the same thing:

VMG = (DTF[t] - DTF[t+x]) * 3600 / x

where x is the difference in time between two positions in seconds. For x -> 0 this converges to

VMG = SPD * cos(GCBRG - COG)

For x significantly greater than 0 and small DTF the value of GCBRG is different at time t and t+x, so you can't calculate with the cosine formula for the one hour interval:

You are 5 miles from some point P, which is exactly East of you. You sail with COG 030 and SPD 3 nds for 1 hour (Distance traveled is 3 miles). New distance to point P is 4 miles, bearing is 120. Draw it on a piece of paper, it's a right angle triangle.

So, all in all you decreased distance by 1 mile in 1 hour. So your VMG over 1 hour is 1 nd. Using the cosine formula you get a VMG of 1.5 nds for the begin of the 1 hour interval and a VMG of 0.0 nds for the end of the interval. Both values are of no use to your navigation on OV, as you need to know the average value over the whole 1 hour interval.

Best is to take paper and pencil and draw and thing about some easy examples, like above.

pour completer brainaid

un exemple qui montre que VMG = SPD * cos(GCBRG - COG) est qu'une approximation du au fait qu'ov n'est pas continu mais discret

prenez un angle de 90° par rapport a votre point d'arrivéé

wmg = SPD*cos90 = 0

mais vous vous etes eloigné de votre point d'arrivéé

si ov etait continu on decrirait un cercle, alors qu'etant discret, vous decrivez une droite tangente au cercle

brainaid a écrit:

The detailed classement for the RWC Leg 3 is available at:

http://team-yacht-treff.de/pub/cls-rwc-3.html.

j"adresse une requête au concepteur du tableau de classement: est il possible de figer le volet des titres pour permettre aux derniers dont je fait parti, de conserver les titres de chaque colonne

merci d'avance

par sécurité :

ich schicke eine Bitte am Werbefachmann vom Klassifizierungsgemälde: es ist möglich, um den Letzten zu erlauben, fest werden den Fensterladen der Titel zu lassen deren ich Parteitatsache, von die Titel jeder Säule zu bewahren

I refer a request to the inventor of the picture of ordering: it is possible to freeze the shutter of the titles to allow the last of which I make gone, to keep the titles of every column
thank you for advance

traductions automatiques pas toujours très bonnes!!!