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Tracking the performance

instruments tracking performance wearables training

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#1 Niilo06

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Posted 01 March 2014 - 09:33 AM

Hi! 

 

I'm curious about what are the electronics and methods you use to track your sailing performance & training progress?

 

The main group of my interest are the ones who sail with small performance boats like moths, lasers, F18 & A cats or other a like.

I wish you could shortly explain what is good in your device and how do you use the collected information to track your development.

 

The reason for this is, that I live in area where I unfortunately need to train a lot on my own. This summer I will start to train with an A cat and I want to follow my development on a more detailed level from the beginning. I have used Garmins Forerunner 101 and tracked speed and course info, but I broke the screen of it and now I want to find a new option for my self.

 

Regards,

Nico

 

 



#2 Fleetwood

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Posted 02 March 2014 - 01:53 AM

Use a Speedpuck on our dinghy in speed mode. On board I try to maintain good speed and pick lifts and knocks.

At home, download the track and check tacking angles, how straight a course we sailed to the marks,and try to remember whether deviations corresponded to wind shifts, other boats or our screw-ups! Overlay the track on Google Earth to try and determine the effects of local geography on wind shifts, etc.



#3 henry the navigator

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Posted 02 March 2014 - 05:06 AM

Fleetwood,

 

That sounds great.  Can you show us any plots where you have detected geographic shifts with your technique?  Do you think there is confounding between temporal and geographic shifts?

 

Could there also be errors resulting from differential currents?  How do you deal with velocity shifts and shear?

 

 Instead of trying to remember derivations that correspond to wind shifts, other boats and screw ups, have you considered sync-ing video data to the log files?



#4 us7070

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Posted 02 March 2014 - 01:26 PM

looking at GPS tracks after a race can often tell you whether you were in phase with shifts.., had some bad tacks etc. you may also notice that you are consistently lifted/headed on one part of the course, which may indicate a geographic shift.

 

but as far as any kind of quantitative performance monitoring, i don't think it's really possible - in most dinghy classes, if you are 0.2kt slow, you will be shot out the back.., but there is no way to isolate the effects of good/bad boatspeed from smalll windspeed changes

 

it's actually more difficult than most people appreciate to do _meaningful_ performance analysis from the logs on very well instrumented big boats



#5 allen

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Posted 02 March 2014 - 03:06 PM

In case my point was missed, most GPS logs do not log speed.  (I do not know about the SpeedPuck)



#6 Fleetwood

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Posted 02 March 2014 - 11:47 PM

Henry,we normally sail a fixed course and sometimes get lifts off one of the shorelines. I'd hoped to be able to determine what conditions make it happen by looking at past tracks, so far it seems random! Which it can't be...

Not a lot of current in our bay but there may be a wind speed threshold which turns on the lift. Haven't thought of adding video, that is getting more serious than we want to do! 

7070, agree that we can only get qualitative info. In one area of our course the wind meets from 2 small bays and gets very confused, past tracks can give us an idea of how far away from shore we need to stay to remain in reasonably consistent wind (can tell on the course too if we got it wrong!)

Mainly use the past tracks to look at how good our tacks are and whether we are in or out of phase with shifts (generally out of phase!) For example, last week our tacks were all good except for two disasters, the first when we hit a lull and just had to keep going even though knocked (not enough wind to tack efficiently), the second we had to bear away to avoid dirty air from a bunch of big boats on top of us (we are a small boat in a widely mixed fleet). These 2 cost us several places.

Allen, Speedpucks log speed and position (heading). Upside - very simple to use, downside - relatively few, fixed viewing & logging options.



#7 allen

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Posted 03 March 2014 - 12:27 AM

@fleetwood.  How do you know they log speed?  And how do you read it?  Even my QSTARZ, which absolutely reads speed, writes GPS files without speed (see below).  I can't figure out how to get an output that has speed information on it.  I must admit I have not put a lot of effort into it because I get speed logged from my StartLine program and it just writes a big file that I put into Excel (see below).  I get speed, heading, time and distance to the mark, anything I want but then again I wrote it.

 

Can you post a file from the Speedppuck that has speed information in it.  Just a small sample?

 

Here is a sample of a GPX file with no speed that will show speed in any analysis software, but it is just speed derived from change in location which is not good enough.

 

<trkpt lat="51.632412947" lon="3.858183523">
<ele>36.480148</ele>
<time>2014-03-01T12:32:31Z</time>
</trkpt>
<trkpt lat="51.632446987" lon="3.858111485">
<ele>36.374878</ele>
<time>2014-03-01T12:32:33Z</time>
</trkpt>
<trkpt lat="51.632479017" lon="3.858034351">
<ele>36.204952</ele>
<time>2014-03-01T12:32:35Z</time>
</trkpt>
<trkpt lat="51.632507321" lon="3.857959089">
<ele>35.967152</ele>
<time>2014-03-01T12:32:37Z</time>
</trkpt>
 
See, no speed.  
 
I would love to see the file out of the SpeedPuck with speed information.
 
By comparison, here is the output of StartLine
 
2014-03-01 12:10:32 SVC8 51.606958 3.851992 3.7 298 6 20.13
2014-03-01 12:10:33 SVC8 51.606968 3.851965 3.8 298 5 19.59
2014-03-01 12:10:34 SVC8 51.606980 3.851940 3.9 297 5 19.15
2014-03-01 12:10:35 SVC8 51.606988 3.851915 4.0 297 4 18.86
2014-03-01 12:10:36 SVC8 51.606998 3.851888 4.0 296 3 18.70
2014-03-01 12:10:37 SVC8 51.607007 3.851862 4.0 292 3 18.57
2014-03-01 12:10:38 SVC8 51.607015 3.851832 4.1 291 2 18.48
2014-03-01 12:10:39 SVC8 51.607022 3.851802 4.1 289 2 18.38
2014-03-01 12:10:40 SVC8 51.607030 3.851770 4.2 289 2 18.04
 
The fields are 
Date/Time Waypoint Lat Long Speed Bearing Turn TimeToMark
 
See, speed.  In this case between 3.7 and 4.2 knots.
 
Allen


#8 gjbike

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Posted 03 March 2014 - 12:30 AM

The Prostart logs speed and you can replay your race on their software. Also gives performance stats and can plot polars. 



#9 allen

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Posted 03 March 2014 - 12:38 AM

I will believe it when I can see a file that has speed information. I am not saying I don't believe it, but I have been fooled too many times by programs that display speed but have not really logged it.

 

Allen



#10 allen

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Posted 03 March 2014 - 12:44 AM

I should have said, I want to see the file that is the input to whatever Software they provide.  For example, I just took the sample GPX file I posted (with no speed data) and imported it into OpenCPN and when I display the route it shows speed.  But there is no speed information logged.

 

Allen



#11 us7070

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Posted 03 March 2014 - 12:56 AM

Allen is right  - most programs for displaying GPS tracks calculate speed from distance and time between successive positions.

 

the gps units generally don't log the doppler speed displayed on the unit in real time.

 

so, if the prostart is logging speed, it would be interesting.



#12 allen

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Posted 03 March 2014 - 01:24 AM

From the GPX specification, you would want the input file to the program to have this kind of field in it.  There would be a similar field for <COURSE>

 

<wpt> <rtept> <trkpt>

Units: meters per second

<speed>4.23</speed>

Instantaneous speed at the point.



#13 henry the navigator

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Posted 03 March 2014 - 02:08 AM

Fleetwood,

 

Check for current.  It will save you lots of pain in the long term. 

 

Post graphics if you have em.  There is a lot to learn from good quality data.   The first step is getting good data and proving that it is good.



#14 henry the navigator

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Posted 03 March 2014 - 05:53 PM

This is the type of real time analysis that some can do.

If you want to know more I can explain it.

This is called a BET diagram. It shows you when you can gain by tack and when you can only lose based on environmental conditions.

https://www.dropbox....2014_124145.png

#15 henry the navigator

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Posted 03 March 2014 - 06:46 PM

Niilo06, drop me a line if you want to know more.



This is an annotated tack: https://www.dropbox....a3a/Tacking.pdf

#16 gjbike

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Posted 04 March 2014 - 05:07 AM

This is the software that Velocitek sells with the Prostart.THere is a free similar  program that comes with the unit. I can't speak as to how exactly it's done but I can get contious readout of speed on the playback. It also gives angle off the wind ( to a refernce point) and mean speed and VMG with adjustabe parameters. 

http://gpsactionreplay.free.fr/



#17 us7070

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Posted 04 March 2014 - 01:36 PM

This is the software that Velocitek sells with the Prostart.THere is a free similar  program that comes with the unit. I can't speak as to how exactly it's done but I can get contious readout of speed on the playback. It also gives angle off the wind ( to a refernce point) and mean speed and VMG with adjustabe parameters. 

http://gpsactionreplay.free.fr/

 

GPSAR was originally written for use by windsurfers with "normal" GPS receivers.., those that do not record doppler speed. The program calculates it from position and time.



#18 allen

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Posted 04 March 2014 - 11:49 PM

This thread inspired me to write down what I was doing in analyzing a recent race.  We were concerned why we missed the layline and wanted to make sure the analysis we were doing was correct on the one hand, and figure out how to do better next time, what further analysis might we do to help if a situation like this came up again on the other.  The conclusion was that the boat was not sailing to its target AWA.  We are working on how to determine that on the water and have some good ideas but not complete.  I thought this write up would be of interest to people in this thread as it is a little different than the typical post race analysis I have seen.  I should say that the reason this was a question was that we have a boat going 6 knots in 2 knots of current.  The current changes things.

 

http://l-36.com/AnalysisOfATack.php

 

AnalysisOfATack_CalculateCurrent2.png

 

Hope you enjoy it.

 

Allen



#19 Fleetwood

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Posted 05 March 2014 - 12:56 AM

Velocitek says that it gets Speedpuck speed from the time signal doppler shifts and the data shows position, time and speed, but I'm not able to pull apart the .gpx and (their) .vcc files to see what's actually logged. (I suppose I could ask them!)



#20 allen

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Posted 05 March 2014 - 01:07 AM

^^ It is certainly true that they use the doppler shift and time to display the speed and direction.  It would be useless on the water if they didn't.  That is, however, a completely different question from what they log.  I have a QSTARZ which logs speed and direction from the carrier shifts but I have no idea, even given that, how to get a file with that information in it.  The GPX files they generate only have time and position.

 

You can read a GPX file with any text editor.  Just open it.

 

Look for the section with the tracking points like this one:

 
<trkpt lat="51.602851512" lon="3.845418040">
<ele>35.280807</ele>
<time>2014-02-01T11:14:45Z</time>
</trkpt>
 
 
And see if they have speed.  This one has latitude, longitude, and elevation along with the time to the second.
 
Excel will read it and decode the XML and put everything in columns for you.  Word will open it as well.

 

Allen



#21 Fleetwood

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Posted 05 March 2014 - 04:17 AM

Yeah, the text editor shows that the .gpx file has only lat, long and time. My uncertainty was that the .vcc file shows speed as well; I'd opened it in Excel and gpsactionreplay.



#22 allen

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Posted 05 March 2014 - 04:28 AM

^^   You probably already found this:

 

These instructions are based on Excel 2010:

1. Select File>Open

2. Change file type from "All Excel Files (*.xl;*.xlsx,*xlsm;..." to "All Files (*.*)"

3. Select the .vcc file you want to view in Excel

4. When Excel warns that the file is in a different format than specified by the file extension, choose to open the file anyways

5. Choose to open the file as an XML table

6. When Excel warns that the specified XML source does not refer to a schema, select OK 



#23 Fleetwood

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Posted 05 March 2014 - 04:38 AM

Yeah, that's what I did but its no different from what's in gpsactionreplay and led me to think that I might be getting speed till I opened the .gpx file in Notepad and saw no speed.

Oh well!



#24 allen

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Posted 05 March 2014 - 05:20 AM

^^ so you are saying that the .vcc file is an output file?  A good example of why you have to look at the input file :-)

 

For a lot of what I do it really doesn't matter because I average over such a long interval that either one is fine.  But there are other times when you want instantaneous speed.  For example, we did some experiments where we tried different turning rates and exit angles.  I think the best was a slow turn and exit a little low and build up speed, then head high.  For that you need good speed data for every point.

 

It really depends on what you want to do.  I just wanted to make people aware that they are not getting accurate speed data out of a program that does't have it going in.

 

Allen







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