Facebook

Login

Support Sailonline

If you haven't already - join the SAILONLINE YACHT CLUB!

Please also consider making a donation - all amounts are greatly appreciated!

Board » Technical Support » qtVlm thread

Page: First Previous 23 24 25 26 27 28 29 Next Last

Looks like it's working. The link was missing the .exe which I've updated below.

Thanks

https://www.virtual-winds.org/maitai/qtvlm_setup_5.8.6-beta4.exe

In past years we saw a quick evolution not only on weather routing software but also on sidekicks aiding tools.
One of the best weather routing programs used around the corner is qTVlm. Since the very first versions it has been upgraded in a good rhythm bringing also a plethora of innovations, sometimes using info and suggestions gathered from the community.

Anyhow, one qT aspect that has been roller coasting is the Optimizing/Simplifying algorithm processes applied to the calculated routing WPTs.

It is very simple to verify that in spite of using the “Optimum Simplify” process first, and "Optimize" after (applied only once or several times), normally we won’t get the best ETA - even before any trimming operation on the fixed calculated WPTs, the ones in “red” color generated around land/rocks/barriers and on the remaining "green" movable ones.

The cause for this is identified. Is a direct consequence of the used decimating algorithm implemented in qT for the “Simplify”/ “Optimum” processes.

In recent versions - 2018 - this issue was aggravated as the decimating operation during the “Simplify” process stopped being uniformly applied along the routed path, leaving us to the somehow paradox of having more remaining WPTs in the end of the route, precisely where the predictability of the WFs are worse, which is a contra sense.

There are ways to overcome this issue but, again with another contra sense, as you have to spend more time rehabilitating an over decimated routed path by adding new WPTs.

Every WPT over decimated is a less one degree of freedom in the generated curve, giving here the main reason for qT going in opposite direction of the optimum ETA.

Sincerely hope that qT responsible persons take once for all this issue and, at least bring back the “old” decimating algorithm, the uniform “cutter”.

João/psail
Sail Fair.
Joao, you should also mention that you are using settings that I strongly say you should NOT use...

Running a routing with 5mn isochrons can only lead to disappointment in most cases. If I allow for 1sec isos would you use it? 1ms even better? Even less?

Using such a small amount of time between isos creates way too many points that are likely to look useless to the simp process, which can only do what it is aimed to do: simplifying (i.e. remove the point if the ETA is not worst). Since there is not enough room between points it will end up by over simplifying.

Conclusion is that there is a good reason behind the default values, what else can I say? Modify them at your own risk, but do not complain if you don't like the result.

I could add a few things:
1) Routing with 5mn interval on a 3 days travel is just ridiculous knowing that the real wind is different from the grib's wind and that anyhow next grib update will just completely rebate the cards.
2) qtVlm is not specifically designed for SOL and will never be. qtVlm is designed for real sailors or racers and does not try to give an exact answer to an infinite problem. It is just a toolbox that can help to decide where to go.
3) qtVlm is also used in official scientific projects and is also used by very famous racing teams over the world. No one is using 5mn isochrons, there must be a reason.
4) We are opened to suggestions and improvements and even complains. But it need to be reasonably compatible with the real world, and concerning bugs it needs to be reproducible with reasonable settings.

Happy Xmas to all
Philippe.

--- Last Edited by maitai at 2018-12-25 14:16:38 ---

--- Last Edited by maitai at 2018-12-25 14:17:03 ---
Hi Philippe and all.
Good afternoon.

Well, the settings I’ve been using a long time (since they were available) are the same, so I don’t have any induced distortion on comparing results generated with different settings.

Those settings have proved to give results in all kind of WFs and with different boat Polars, being also more relevant with the faster boats, as you easily understand and as per example I sent you recently.

Correct, the lower the Time Step (TS) used for calculating the Isochrones, the bigger will be number of potential WPTs. That’s the price for getting precision.

The first point you mention misses rationality.
We all know that ANY GRIB file won’t be exactly what you are going to sail IRL. Under that argument - yours - I ask why do we make routings?

I totally agree with your second point and part of the third. For that I can give you one plausible answer for people not using TS = 5 minutes: I takes a lot of time to get a result, not because is less precise.

In relation to fourth point, previously I gave you a suggestion: bring back the old "cutter", which I now reiterate.

If it doesn’t have anything to do with the used TS, what’s the problem for implementing it again?

My Dear Friend have also
a Merry Xmas

João/psail
Sail Fair.
Hi there maitai and oxygen 77. I'm writing to you as the original "matchmaker" between QtVlm and sailonline.
I am sorry to tell you that Joâo/psail have suffered from a heartattack and has deceased.
He's very missed in SOL as you can read in other forum posts, and I'm also sure he'll be missed as a very determined "hawkeye" to whatever the small issues could be in our use of your absolutely amazing program.
It's my hope that someone else in the SOL community will be as sharp as he was.
But again - SOL, as a whole, is MORE than satisfied with using QtVlm.
Thank you again :-)

--- Last Edited by Bimmer at 2019-04-29 14:01:00 ---

--- Last Edited by Bimmer at 2019-04-29 14:01:51 ---
Very sad news. We had a lot of exchanges to improve qtVlm usage with sailonline.

All my thoughts to his friends and family.
skippers,
Concerns QtVlm version 5.8-9
If you export a QtVlm-route to csv to generate values for brainaids dc-tool you will see that QtVlm has inserted some new columns.
COG is found now some columns to the right.

If you use your 'old' convertor now you get knots in stead of degrees you expect.

greetings
LacSareno


--- Last Edited by sol at 2019-05-05 17:14:41 ---
Solution:
Change SOG to COG(T).
See screen shots.
Also works for AGL.

--- Last Edited by Bimmer at 2019-05-06 11:46:50 ---
Attachments
@Bimmer,
Are you sure you want to use AWS for sign of TWA? I think TWA now will get always the same sign.

LacSareno


--- Last Edited by sol at 2019-05-07 14:01:14 ---
I'll look into that, thanks LacSareno :-)

Page: First Previous 23 24 25 26 27 28 29 Next Last

Please login to post a reply.

Races

Next Race: 00d 00h 00m


Current Races:

Melbourne to Osaka 2023
Welcome to Melbourne for Sailonline's alternative version of the Melbourne to Osaka Double Handed Yacht Race - a 5000 nautical miler. This year again we're racing the RP-66, but the route is unlimited what comes to waypoints. Because the IRL version does not run this year, we took the freedom to make our own route!
It could be a long race, east or west, and of course some doldrums to negotiate!
PRIZE: SMPF
Race #1679
INFO by brainaid.de
RP-66 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking:
OCQ2 - OCCH - SUPSOL - SYC
Race starts: Apr 01st 02:00 Registration Open!

▶ Flash
GO TO RACE

Sail Around Turkey 2023

This is one of Sailonline's iconic and more challenging races. Our IMOCA 60 Foil high-speed yachts will sail across three seas (Black Sea, Sea of Marmara, Mediterranean Sea) and two beautiful straits (Strait of Istanbul - Bosphorus and Strait of Canakkale - Dardanelles). Altogether 1372 nm of great and demanding sailing from Hopa (the easternmost point of the Turkish Black Sea coast) to Iskenderun (the easternmost point of Turkey's Mediterranean coast). Get ready for a lot of fun; we are waiting for you at the starting line.
Race #1665
INFO by brainaid.de
IMOCA 60 Foil PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking:
ARQ1 - ARCH - SUPSOL - SYC
Race starts: Mar 21st 15:00 Registration Closed

▶ Flash
GO TO RACE

Sinbad Seeks Spices 2023
Having surveyed Arabia, Sinbad Al-SOL’er next invites you to race him on his second of seven epic voyages to every corner of the Indian Ocean and beyond, this time to seek spices in Zanzibar, departing from Xaafun, a trading post on the tip of the Horn of Africa since the days of the Mycenaeans and on through Roman times to the Nights of 1,001 of AL-Sail’or, Al-SOL’er’s illustrious ancestor. SOLing by the sun and the stars, aka seat-of-the-pants, the voyage will take you east as far as Praslin island, south as far as Anjouan, to Zanzibar’s Unguja for all things spices, but only back as far as Mogidishu – another exhausting 3000nm adventure, this time in Reichel/Pugh 66s.
Race #1637
INFOby brainaid.de
Reichel/Pugh 66 PARTICULARS
WX Updates:
0430 / 1030 / 1630 / 2230
Ranking: SYC - SVS
Race starts: Mar 19th 09:00 Registration Closed

▶ Flash
GO TO RACE

Go to race archive

SYC Ranking

  1. Sailonline Yacht Club Member WRmirekd
  2. Sailonline Yacht Club Member FreyjaUSA
  3. Sailonline Yacht Club Member Pit8008
  4. Sailonline Yacht Club Member Vida_Maldita
  5. Sailonline Yacht Club Member rafa
  6. Sailonline Yacht Club Member Kipper1258
  7. Sailonline Yacht Club Member Sax747
  8. Sailonline Yacht Club Member sassy63
  9. Sailonline Yacht Club Member TarassBoulba
  10. Sailonline Yacht Club Member CollegeFund

View full list

Series

Mobile Client

SYC members have the benefit of access to our mobile/lightweight web client!

The mobile client