Vendee Arctique
Post by iconPost by Luis75 | 2020-07-08 | 17:46:10

Hi all,
today I noticed on VR that buoy #3 has been moved towards east. Is it me or it really happened?

commenticon 37 Comments
Post by iconPost by Luis75 | 2020-07-08 | 17:47:20
I would say towards north-east and the new position is quite faraway from the old one
Post by iconPost by BooBill | 2020-07-08 | 18:47:29
Jacques Caraës, Race Director of the Vendée – Arctique – Les Sables d’Olonne:“By repositioning the Gallimard mark, Race Management and the weather cell are simply trying to refine the ETAs (estimated time of arrival). A high pressure system is settling in over the Azores, which the back runners might well have become ensnared in if the initial positioning had been retained. Positioning the mark at 46°20N – 015°W enables us to pretty much stick to the initial format of around 12 days. It is likely there will be a bunching up of the fleet with around thirty hours separating the first and last boats. The skippers in the Class IMOCA have really had their work cut out in the first part of the race. When you sail a course from north to south, you know that you’re going to pass through various weather systems rather than accompanying them: low pressure systems, ridges of high pressure, sustained or light winds, all of which enable you to play around with strategies and work on points of sail. This is evidenced by the fact that the IMOCAs with classic (straight) daggerboards are still in the match and it’s very difficult to predict who will make the podium!”
Post by iconPost by UUnet | 2020-07-08 | 20:10:20
Thx @BooBill
Post by iconPost by Luis75 | 2020-07-08 | 23:20:05
Thank you @BooBill
Post by iconPost by etrille17 | 2020-07-09 | 07:39:49
Merci pour les explications qui sont claires et nettes.
Post by iconPost by Luis75 | 2020-07-09 | 09:48:18
Re: passing buoy #3. Is it possible in your opinion to pass west of the buoy cross the line I see on the dashboard and come back?
Post by iconPost by Hardtack | 2020-07-09 | 10:52:49
No, I don't think so (assuming you mean the IOC UNESCO mark at 62°N 25°W). You have to go counterclockwise around it.
Post by iconPost by Luis75 | 2020-07-09 | 10:58:29
Yes I mean IOC Unesco mark. Well next time I use a guest account and I try it...
Post by iconPost by Luis75 | 2020-07-09 | 10:58:41
Tx!
Post by iconPost by YourMomSA | 2020-07-09 | 20:14:44
Anybody know much about how VR processes waypoints relative to mark validations? For example, is there an oddity if you hit multiple course changes due to waypoints all within the same minute?

I had two waypoints at the turning mark. One just NE and one just NW, and then a third down S. But it failed to validate the mark. I've used similar techniques plenty of times before without problems. I'm not sure what happened. It looks like Titanic and Kallemans had similar issues. Presumably others too. Unfortunately, I was in a business meeting and didn't notice until 10 minutes later, and then I had to focus on work so I couldn't even hand-steer it properly. So I must have lost half an hour or more. Might get some of it back with fleet compression, but the race is shot.

it's ok... I can live with it. It happens to everyone occasionally, particularly if you try to push the limits on roundings. And I set those waypoints on my phone when I woke up around 6 AM, so maybe I simply got it wrong and failed to notice.

Looking at my track, it doesn't look like my boat ever turned West. It looks like it went to the NE waypoint and then turned South. So I've been wondering if maybe it processed both waypoints in the same minute and somehow got confused.

Either that, or maybe being so far North on the map confused it. Maybe when you're North of 60N, you need to sail more than 2 or 3 second of longitude to register the movement? Now that I think about it... I'm starting to think that's the most likely explanation... since it seems to have been an issue for more than just me.
Post by iconPost by SlyStarLeRetour | 2020-07-09 | 21:36:04
Hi
We experienced same issue with some of our team members; coordinates were similar but some passed and some did not. Strange.
Post by iconPost by smit | 2020-07-09 | 21:50:59
I was 30-40 minutes behind you and noticed your routing change to make the mark. I looked at mine - similar three waypoints (but I haven't gotten as fine tuned as you and the other leaders). The buoy had not turned green and the rotating arrows still indicated I needed to round the mark but I was SW of the mark already. I hesitated for a few minutes and when I went back it had changed to green. My routing at that time showed the horizontal offset typical when changing course and VRs dead reckoning issue. My track shows the turn south (at waypoint 2) much further west than I had set it.
Post by iconPost by Hardtack | 2020-07-09 | 21:42:09

There is one thing I noticed today when fine-tuning my waypoints. I first had two waypoints at the same latitude 62°00'01", but they weren't aligned on the Dashboard map as I expected. I thought that waypoints are placed at integer second coordinates, because that's what the VR interface suggests. Alas, as with heading/TWA, this turns out to be wrong.

This is what I got when I just set a waypoint at 40°00'01"N 70°00'01"W in the Atlantic Record with a guest boat:

{
"@class":".LogEventRequest",
"eventKey":"Game_AddBoatAction",
"race_id":436,
"leg_num":1,
"ts":1594329240000,
"actions":[
{
"values":[
{
"lat":42.00047,
"lon":-70.00054,
"idx":1}],
"aground":true,
"nextWpIdx":2,
"type":"wp"}],
"requestId":"637299332278370000_381"}

So the longitude value actually is 70°00'01.9" !

I didn't do the math, but obviously when trying to round the mark with a 1" margin
on the VR display, things can easily go wrong. It seems that I was lucky this time.
Post by iconPost by YourMomSA | 2020-07-09 | 22:00:04
Very interesting, thanks. My waypoints were set on my phone, so no dashboard. I set them at

62 00 01, 24 59 59
62 00 01, 25 00 01
61 58 00, 25 00 00

If I had been on my computer and looked at the dashboard, would the dashboard have shown the true locations?

Stil uncertain though how that arrangement could have missed the buoy validation, even if they were off by half a second. Unless the discrepancies can be off by more than that. I guess I need to give it a bit more margin in the future. Particularly in extreme latitudes, where coordinates can get a little squiffy.
Post by iconPost by Hardtack | 2020-07-09 | 22:28:16
The dashboard shows the true locations on the map, but it does not display the numeric lat/lng values. Actually it only shows line segments between the waypoint, something that could be improved.

If your bearing to the first waypoint was 8° or 10° and the actual latitude was, say, 24°59'59.95" then you may have missed the mark (I think, haven't done the math).

But if you say your boat never turned west I don't understand how this could happen. It should have sailed at least 1" between the NE and NW waypoints.


Edit:
Note that VR are truncating the centiseconds. The positions can be off by a whole second away from the equator / Greenwich.


Post by iconPost by YC6211 | 2020-07-10 | 00:34:37
I had the same waypoints set initially, but after playing around with a great circle path tool I noticed that the bearing from 62 00 01, 24 59 59 (WP1) to 62 00 01, 25 00 01 (WP2) was the same as from WP1 to the mark. It didn;t have the resolution confirm whether it passed north of the mark or not, but it was withing a few meters either side. It's possible that this route didn't actually pass to the north of the mark. I set my WP to 62 00 01, 24 59 59 and had no issues.
Post by iconPost by Luis75 | 2020-07-09 | 22:38:48
One more thing: I noticed that the mark on vr was not exactly positioned at 62N25W.
Fine tuning the wp, I noticed that setting the wp west of the mark at 62N 25°00'01' (01' should be around 30 meters) the wp was east of the mark. I don't know if this is a graphical problem of the VR interface or if it has something to do with the discrepancy you mentioned. As I said that difference of 0.9'' should be around 30 meters (27 exactly) which is quite a lot when you push the passage. Then I moved the third wp at a safe distance, but in this way I lost something like 40 positions.
Post by iconPost by Hardtack | 2020-07-09 | 23:00:39
No, according to the Game_GetBoatState message the mark is at 62N 25W exactly. The VR interface is too inaccurate, you won't be able to see it there, even if you use a waypoint to check the position, because VR are truncating the centiseconds. See above.
Post by iconPost by YourMomSA | 2020-07-10 | 00:05:47
Thanks, guys. I think this explains it. I've done hundreds of races, and when you push the limits, you'll occasionally miss a mark or run aground. It's impossible to know if my boat actually turned West or not (Waypoint 2 said it should have sailed 253 for a seconds of longitude), but even if it did, it sounds like the rounding of centiseconds, plus my boat coming in at 008, must have tripped it up. Either that, or due to the northern latitude, my Westerly leg was so short that it somehow confused the buoy confirmation logic. I think the northern latitude must be part of it, simply because the problem happened with more racers than usual.
Post by iconPost by BooBill | 2020-07-10 | 00:59:37
Follow up question. Since waypoints can only be set using the graphic interface (please tell me if there is another way), the finest you can get it is 1 pixel, right? If you set your waypoints using a higher resolution screen, can you get greater accuracy?

After grounding countless times I now try to set waypoints in fullscreen mode on my 27" iMac. Visually you can see a lot more, but is that actually giving you greater fine control than say using a phone screen?
Post by iconPost by Hardtack | 2020-07-10 | 09:19:08
If you spin the helm control counterclockwise several times, the unity player shows some setup and debugging info, including the screen resolution. Mine says 1080x574. Be careful, the info is overlaying the game interface, but the game interface still works.
I was just reminded of this when I turned my boat around 180°...

Post by iconPost by BooBill | 2020-07-10 | 12:21:06
Remind me to try that AGAIN when I don't have program points set. You warned me.
Post by iconPost by Hardtack | 2020-07-10 | 12:46:31
Lol. I kept further west than most of the fleet after the UNESCO mark and I think this gained me a few places. Not sure why I tried to ruin my race. I usually use a guest boat for experiments.
Post by iconPost by YourMomSA | 2020-07-10 | 13:52:14
I hope your decision to stay a little West pays off... I stayed... a little more West. (25W had the max breeze for a few hours, so I sailed straight down it, with an attitude of "I shanked this race, so I'll do this now and figure the rest out tomorrow". It was that or Raketa's move East. I liked that move, but wasn't quite far enough back to take that big a risk. I think he's going to be looking pretty good in 12 hours or so... and then will drop back when he has to deal with headwinds... unless the forecast changes.

Oh, and... I like your team.
Post by iconPost by Hardtack | 2020-07-10 | 23:01:02
Thanks :-)
Post by iconPost by MidnightFoiler | 2020-07-11 | 04:21:04
Interesting YM, I'm not sailing with full options this race but just to gain some VSR points and so decided to push that one to the limit as an experiment and passed ok.

My coords checked in dashboard raw log were
62.00018 -24.99986 - only 21m NE of mark
62.00001 -25.00008 - only 4.5m W of mark
and then south at heading 182 to a wpt much further out that I went back in and deleted.

I wonder if I got lucky and my 2 wpts happened to not be in the same minute on the server? 25m would have only taken about 4 secs so that's a 1 in 15 chance.


There was me thinking I have finally found one aspect of the game that was accurate a reliable!

Might finish my Atlantic card collection run with a series of wpts 20 secs apart and see if any appear to be ignored...



Post by iconPost by MidnightFoiler | 2020-07-11 | 09:33:27
Did my experiment. I put in 6 waypoints about 20 secs apart and it followed them all according to dashboard track. If it combines within 1 minute then it should have skipped 2 or 3 of them...
Post by iconPost by YourMomSA | 2020-07-11 | 12:36:55
Maybe I just botched it on my phone right after waking up. I'd say that's likely if not for the observation that a bunch of other people similarly missed the mark. Weird.
Post by iconPost by BGSteMarine | 2020-07-11 | 13:34:27
Hi YMSA. You have probably encountered the same problem as some players from my team, and passed left of the buoy with your 1st Way Point.
The truncation of the subsecond decimals on VR User Interface has been fatal !
A little schema for explanation :



Post by iconPost by BGSteMarine | 2020-07-11 | 13:35:27
Ooops !! Image too large ! sorry about that. I have had to try a couple of times ;-)
Benoit

Post by iconPost by YourMomSA | 2020-07-11 | 15:39:03
Great analysis! An additional thought on this point... Your diagram uses squares, but at such a northern latitude, it would be more like narrow rectangles... which would probably exaggerate the implications. It simply never occurred to me that an angle of roughly 8 degrees could possibly be enough to miss to that side.
Post by iconPost by BGSteMarine | 2020-07-11 | 22:50:27
You are 100% right! I made a projection on a square diagram, but with spherical math calculations. This is why the apparent angle on the diagram is greater than 8 degrees.
My first calculation tool was based on plane geometry and I missed one buoy with that ! I'm now using spherical formulas in my excel tool.
Sample for your case if your way point where at 62�00'01.7" and 24�59'59.7" (sorry, it's in french, but the visual is quite clear) :



Post by iconPost by MidnightFoiler | 2020-07-12 | 12:06:09
I assumed it rounded up/down the seconds but sounds like you are saying it truncates down always Benoit?

I just brought up YM's track in dashboard without all the others in dashboard and it does indeed show the arrival from west of the bouy. Oddly the exit is the east of the bouy until you turn around to come back. So it would still seem there was something wrong with the 2nd waypoint (or the track is incorrect) .... and if it was a real race you would need to go back and re-round as all you did was unwind your rounding the wrong way :-P
Post by iconPost by BGSteMarine | 2020-07-12 | 17:27:27
Yes. It's not a rounding but a pure truncation! So the uncertainty is of 1 second and not 0.5 :-/ We need to be careful, or to look at the sub-second decimals for the buoy and the WP positioning.

For YMSA trace, not sure, but I have noticed that for my team members who have had a very aggressive turn with 2 way points within the same minute, the trace seems to only show the second WP, and erase the 1st one ...
Post by iconPost by PML | 2020-07-12 | 23:13:22
Do we also have to worry about the heading displayed in the Waypoints window (which is always an integer) to be either truncated or rounded up ?
Post by iconPost by MidnightFoiler | 2020-07-13 | 01:18:53
Note the next waypoint is shown in the dashboard as 46 20 00N 15 00 07W is dashboard but this is also truncated from 46.333604812622, -15.002098083496 = 46º20'0.977"N 15º0'7.553"W

@PML It must be rounded or truncated. Hard to say which. Possibly rounded since boat heading or twa appears to be rounded. This tends not to be so critical but I would always try to have a degree margin on twa if trying to avoid an auto sail change and a few degrees while on waypoints or heading.

@BGSteMarine I tried to reproduce the ignoring of waypoints with a series of 6 wpts 20s apart but it showed them all in the track. Maybe they need to be closer and/or a more radical change of direction than I tried. I have not seen this problem myself and have done similar things quite often. YMSA's track seems to have the 2nd waypoint ignored not the 1st.

Post by iconPost by YourMomSA | 2020-07-13 | 04:07:05
It's seriously possible that I simply made a stupid mistake on my phone at 6 AM and placed the second waypoint on top of the first. I thought I did it properly, but who knows. It's hard to even get my eyes to focus well enough to read the numbers in that situation. :-)
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