Apps with wind estimation - SailNet Community
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post #1 of 12 Old 08-14-2017 Thread Starter
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Apps with wind estimation

Dear sailors,

The world of computer science needs your help!

Within the framework of my master thesis I am developing a solution for wind estimation. The solution will use GPS track and boat’s polars as input in order to determine the direction and speed of the wind.

Right now I am conducting a market analysis for existing solutions with similar context.

Do you use any application software (smartphone apps, web apps, pc/mac software) with wind estimation functionality?

Such software may guess maneuver types like tacks/jibes and give feedback about your sailing performance without the need for wind measurement instruments and manual wind data input.

It would already help me if you just right the name of the application you are using.

*

Any additional feedback about the application usage will be much appreciated.

*

I am specifically interested in the following questions:

·***** How accurate is the estimation?

·***** What do you have to do/how do you have to sail to receive a correct estimation? (e.g. perform specific maneuvers or sail in 3-4 different points of sail)

·***** What kind of data is estimated? (e.g. wind speed and direction, sea state, wind gusts, estimation confidence, change of wind direction and wind speed)

·***** How does the application react on wind changes?

·***** What does the application show if it doesn’t have enough data collected to make a confident wind estimation, for example when the application is starting to record your track?

·***** What is the main purpose of the app?

Do not hesitate if you want share any further experience and impressions. Feel also free to ignore the questions above and leave a feedback in free style

**

Cheers

*

paddle_master
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post #2 of 12 Old 08-14-2017
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Re: Apps with wind estimation

If I'm following your question, this is what a standard wind instrument does, when tied into a boat's speed and wind sensing systems. Further combined with a chartplotter, using GPS location, many will also determine VMG. I'm not sure how the boats polars come into play.


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post #3 of 12 Old 08-14-2017
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Re: Apps with wind estimation

I don't think this is terribly useful where there are lots of currents and eddies.

What sailors need is more reliable and accurate transducers for wind speed, angle and boat speed... and then with the polar diagram data a program can be used to help them predict tacks and so on as the B&G touch does.

This would interest racers.... mostly I suppose.

Sailors who are going from here to there do need reliable current information along with accurate wind info to inform their trim and course.

Sailors who sail in familiar waters will learn how the wind and currents are... and their GPS plotter tracks are easy to eye ball for predictions on when to tack.

Last week I was faced with a typical situation and could without much effort by just referring to the track on the plotter in the cockpit predict how many tacks and where to tack ...would be required to reach the entrance buoy. I was correct and having more accurate info might have saved me a few minutes. So what? No hurry. I was not racing.

Thanks but no thanks....

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post #4 of 12 Old 08-14-2017
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Re: Apps with wind estimation

Here ya go: SailTimer Wind Instrument? .... look in the description of this app to see if that matches your marketing research efforts.
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post #5 of 12 Old 08-14-2017
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Re: Apps with wind estimation

I think that what you plan is to take the GPS reading (actual speed over ground) and the boat's polars (an ideal version of how fast it ought to sail at various wind directions/speed) and use that to back-calculate the actual wind speed. I don't see how you can do that without knowing accurately what the current speed and direction are because they will throw the speed/direction off in unpredictable ways Also, how many boats sail exactliy to their polars? I have never worked with them so really don't know. Have you done any kind of analysis to see how much your calculated wind speed would be affected by a given amount of error in the input (ie the polars say 5 knots at 5 knots of wind and AWA of 120 but the boat is actually only going 4.5 knots through the water because the bottom is dirty?)

Am I missing something?
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post #6 of 12 Old 08-15-2017 Thread Starter
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Re: Apps with wind estimation

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Originally Posted by danvon View Post
I think that what you plan is to take the GPS reading (actual speed over ground) and the boat's polars (an ideal version of how fast it ought to sail at various wind directions/speed) and use that to back-calculate the actual wind speed. I don't see how you can do that without knowing accurately what the current speed and direction are because they will throw the speed/direction off in unpredictable ways Also, how many boats sail exactliy to their polars? I have never worked with them so really don't know. Have you done any kind of analysis to see how much your calculated wind speed would be affected by a given amount of error in the input (ie the polars say 5 knots at 5 knots of wind and AWA of 120 but the boat is actually only going 4.5 knots through the water because the bottom is dirty?)

Am I missing something?
The approach is a nice starter. But for a master thesis it's not enough. I will evaluate multiple approaches for wind estimation. Among them neural networks and graph modelling with costs assigned to each edge. There multiple characteristics which may be extracted from GPS and polars. From GPS track I am able to recognize maneuvers. I am able to analyse maneuvers considering different correlations which I have already collected from data mining. For instance: speed change during jibes is less than during tacks. Polars may give a clue about optimal tacking angles and speed ratio between sailing upwind and downwind. It is not possible to sail against true wind without slowing down. All that information may be aggregated for estimation of true wind angle. With some curve fitting of actual and target polar chart it is possible to guess at least some wind speed just as reference.

The solution I am developing is not supposed to replace any wind measurement systems with high accuracy. Instead it should be used for race analysis to produce a default wind information for cases when no wind tracking has been made. Until now Raceqs is the best example I have.
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post #7 of 12 Old 08-15-2017
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Re: Apps with wind estimation

Frankly I think what you are trying is doomed to failure. You just don't have the right kind of data to really extrapolate what you are trying to accomplish. You might be able to get to first order correct, but thats about it. It would be very much like trying to map the bottom based upon wave height and spacing... sure there is some correlation between bottom contours and wave propagation but it isn't tight enough to really derive bottom shape from it.

But if you want to move forward anyway...

The best program I know of to generate 'as sailed' polars is GPS Action Replay. It will generate 'as sailed' polars from GPX logs and is very widely used in performance sailing. The problem of course is that it cannot generate wind speed from GPX files, though it can generate wind direction (though on very fast boats it often flips the wind direction).

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Re: Apps with wind estimation

This sounds like you plan to radiocarbon date old broken clocks, in order to determine the precise two times a day that they read correctly.

All your source numbers are coming FROM a boat. To estimate the wind speed AT the boat. Which the boat already can read directly.

Perhaps something is lost in the translation from hexadecimal ?
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post #9 of 12 Old 08-16-2017 Thread Starter
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Re: Apps with wind estimation

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Originally Posted by hellosailor View Post
This sounds like you plan to radiocarbon date old broken clocks, in order to determine the precise two times a day that they read correctly.

All your source numbers are coming FROM a boat. To estimate the wind speed AT the boat. Which the boat already can read directly.

Perhaps something is lost in the translation from hexadecimal ?
Depends on the boat and it's gear. But as I said. The purpose of my work is not about replacing the wind measurement instruments. It is supposed to add the ability to sailing software to estimate the true wind angle and true wind speed if there isn't any wind information available.
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post #10 of 12 Old 08-16-2017
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Re: Apps with wind estimation

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Originally Posted by paddle_master View Post
Depends on the boat and it's gear. But as I said. The purpose of my work is not about replacing the wind measurement instruments. It is supposed to add the ability to sailing software to estimate the true wind angle and true wind speed if there isn't any wind information available.
This is starting to sound like you are trying to invent a way to see through a wall, when one could easily install a window. Wind instruments already exist that are superior to what I think you're trying to estimate.

I think I follow the back door analysis you trying to contemplate, which would require knowing the boats ability (polars) to sailing in given winds. However, there are too many independent variables you would need to know. Sail trim, sail condition, vessel weight, variability in wind speed from the surface to the top of the mast, etc. Polars are not very accurate, ultimately. They are only approximations themselves.

Further, I think there will be multiple answers to the analysis. For example, from the top of my head, my boat will move at the same speed and track with 10 knots of wind off the bow as it will with 15 knots off the stern. How do you contemplate determining which one is happening?

Finally, GPS track is missing the variable of current. Let's just say that current was precisely opposed to the direction and speed through the water of the boat. The boat would stand still over the ground and show no GPS track or speed, but she is sailing.


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