Expedition Expedition Navigation Software

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Model Accuracy » version 1.200 release & Sailing World article » 11/08/2019 5:48 pm

Version 1.200 has been release!

We have also just released our latest software version 1.200
This is probably our single biggest increment of software release, and it's a BIG step up. We made Model Accuracy more user friendly, more accurate, and more reliable so it's there when you need it most. We hope you enjoy the latest version to help you get to the finish line just a little bit faster!
Here are a list of its improvements:

  • Switched to a new MA Error calculation that is more robust to some "unreal" cases.
  • Switched the TWD correlation from Pearson's to Circular, which gives more appropriate results.
  • Improved output in "stepped" mode.
  • Some vertical compression to fit the UI on smaller screens.
  • Fixed a bug that was causing the UI to slowly getting wider.
  • Added an app icon (replacing the Java icon).
  • Updated help files for changes to the output.
  • Various incremental improvements.

Big  thanks to Dr. Riley Schutt PhD whose feedback and ideas really contributed to this release!

Also, we hope you might enjoy our feature article in Sailing World located here:



Model Accuracy » How does Model Accuracy actually work? » 9/29/2019 1:29 pm

ZeeZee wrote:

Thanks for the response.
I'm with JL:   using GWD and GWS instead of TWD and TWS is essential for Model Accuracy to be useful in areas with currents. 
GWD/GWS are not recorded in the Expedition log files,  but all the data you need to calculate them is there: Set, Drift (I think Leeway is already taken care for in the TWS/TWD of Expedition?).   I'm sure Nick can help you which formulas to use in order to make sure they match up with how Expedition makes these calculations.

Great animation video to show the benefits of MA!!

This is a balance of priorities for Model Accuracy in our development, just as a navigator has to prioritize which GRIB file source to trust the most!

In regards to Ground Wind vs TWD/TWS, we are talking very minor differences in analysis output. 
To be honest, in my entire sailing career, to include Barn Door TransPac wins, Volvo Ocean Race training, ect... I have never heard of Ground Wind until this forum. I am not discounting the point at all, but I think it may show the context of the value of discussing it at too much length. 

There are so many instrument calibrations that are critical to to capturing proper wind data, and a Boatspeed calibration is critical as well, particular for a correct set/drift output. We have all sailed many boats and are very familiar with the poor quality of BSP cals installed on some boats. To create another layer of data conversion now totally dependent on the BSP cal being perfect I dont think is the best use of effort and time right now for our software application.

That would be like debating final 1% of a solution where we have already completed the first 99% of the solution, which didn't even exist until Model Accuracy came about.. 

We can tell the user which forecast is the best, and why. We can help identify time offset trends, and trend errors with recommendation calibrations. 

At the end of the day our mission is to support the navigator by helping them understand wh

Model Accuracy » How does Model Accuracy actually work? » 9/22/2019 1:10 pm

Regarding the first point, it's a matter of definition and consistency. TWS and TWD, although named "True", are usually the wind components experienced by a boat that would be static on water, i.e., moving with any current that prevails. So TW includes the wind resulting from the movement of the boat due to the current.
Ground Wind is the data provided by weather forecast: this is the wind that would be felt at 10-m height by instruments that would be static on Earth, so without any effect of current.
Since we can calculate Ground Wind on a boat equipped with a GPS, I was wondering why you chose TW instead of GW.
This is really of interest in high current and/or low wind situations.

I am tracking. Makes sense. This is actually the first I have ever heard of ground wind terminology. We operate with the TWS and TWD that is provided within the Expedition log files, that is it. We are reliant on the math that produces that number within the log file. 

As for the rest, I really like the concept but find it difficult to work without the ability to shift in time and space. I sail in the Med, where forecasts notoriously challenging. They are becoming better but still tend to suffer a time lag and a spatial shift of some extent. Without accounting for this, it would be dicy to bet on a forecast because it seems to do a better job "here and now" over a given time frame on the boat's course. It will be interesting to see how you handle these shifts.

So the next versions will provide that time shift recommendation. But, currently, with the graphical analysis for TWS and TWD you can see very clearly the lag behind on a macro trend, and then adjust within Expedition routing software accordingly. All you yould have to do is interpret the time scale on the x axis of the graphs. We are working on a forml fwd/backward recommendation time value. 

To better understand this functionality I encourage you to download the software and play around with the test data that is installed

Model Accuracy » How does Model Accuracy actually work? » 9/22/2019 11:19 am

So sorry in my delay here! Here are your answers:

1. Why use TWS and TWD and not Ground Wind data, which is what the forecasts provide?

On the GRIB file side of the equation, TWS and TWD are taken directly from the GRIB file at 10 meter height.
On the wind instrument side of the equation, TWS and TWD are moved from the height of the mast to 10 meter height using the formula available in Expedition user manual. 

The analysis is of the forecast files to what was captured by the sailboat instruments. 

2. What corrections do you apply to TWD and TWS before comparing to forecasts?

Just height correction, so knowing your mast height is critical. And we apply Magnetic variation as necessary to your data if it is not captured raw as True. This way it is apples to apples (ex: true to true) for forecast file to logged data for the comparison. 

3. Is your correlation "static", simply cross-correlating (adjusted) boat measurements and forecasts along the boat course, at the time she was there?


Or do you allow for time and space shifts as forecast may be accurate wind-wise but just offset in time by a few hours or in space by a few (tens of ) NM?

We are working on this. Currently you can easily see how the forecast may lead/lag a big wind shift (ex: frontal passage), but there is no time recommendation in the analysis. Our next version will most likely have that recommendation, just like it recommends increase/decrease TWS and left/right TWD. 

4. Do you have the ability to work with Ensemble data sets?

Yea buddy! Just put all your gribs in the grib folder and let Model Accuracy sort them out. HOWEVER!, if the file names are the same for the GRIB file, you may need to put each file in its own seperate folder to make sure it is havin a fair fight in its evaluation and isnt overlooked. I recommend using this method of that folder structure for really similar named grib files. 

So sorry in the delay! email is at support@m

Model Accuracy » How does Model Accuracy actually work? » 9/22/2019 11:10 am

We just made an explainer video above:

Please checkout the link. 

I will respond in detail. 

Model Accuracy » How does Model Accuracy actually work? » 5/19/2019 9:38 am

Model Accuracy allows a navigator and crew to instantly understand the strengths and weaknesses of particular GRIB sources (ex: GFS, EC, COAMPS, Predict Wind, ect…) and make a more educated and confident decision on which GRIB source to trust the most. The utility of tracking macro and micro shifts in TWD and watching the shifts inside frontal systems is invaluable in understanding the power of each GRIB source. The ability to have absolute confidence in the primary GRIB which you are routing your boat off of is in fact the best GRIB available is truly intangible. It allows the navigator to spend less time in the nav station and more time resting or on deck.

It allows the crew to know the heading and tactics are based off the best information available and nothing was left to just a “gut feeling” or chance.Inside the graphical plots and results pages the user can identify the “tendencies” of each GRIB (forecasting under/over speed for TWS or TWD left or right of actual captured data). Understanding the EXACT tendencies over a selected time period will allow the navigator to correctly twist TWD and raise/lower TWS inside the optimal routing functions of other sailing software. This way the projected optimal course can always be based on not only the most accurate weather file, but the most accurate weather file that is correctly “calibrated” for the current and past forecast errors. 

There are a plethora of GRIB sources, all claiming they are the best source for you and your team to trust as you cross an ocean. Finally there is an application which provides a metric for the consumer, the absolute end user, which ranks the  accuracy of different GRIB sources and exposes their successes and shortcomings. This software was made strictly for you, the sailor.

Professional sailing teams spend massive amounts of time and money constantly refining the VPPs (polars) of the boat to ensure the optimal routing software has the most accurate projected performan

Model Accuracy » v1.102 » 5/19/2019 9:33 am

Version 1.102 has been released! v1.102

  • Fixed locale to US, to avoid problems with differet number formats (thanks to Clement Bourgeois for his help tracking that down).
  • NOAA buoy data fetched for last 45 days (up from 5 days in 1.101).
  • Improved handling of cases where the log and GRIB data don't match well, e.g., they don't even overlap.
  • Change handling of NOAA data to never delete, but to archive old data that is not contiguous with new data.
  • Message window has Clear and Dismiss buttons
  • Various bug fixes.


Also be sure to check out the latest custom weather websites for Around Block Island Race! We added a new custom SAILDOCS grib file subscription template to make it even easier to get grib files while underway!


Model Accuracy » ModelAccuracy » 4/30/2019 1:22 pm


Hey there! We would love to show you a private software demo if you like! just drop us a line and we can get your schedule. We also have a ton of new user tutorials listed here: tutorial page

Make sure to join our mailing list if you like. You can sign up here:  download page

 Model Accuracy can now handle Expedition, Adrena, and NOAA Weather buoy log files so we hope to really saturate the log file analysis market! 

-Model Accuracy

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