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GPS Tracking - Youth Nats 2013 - Eh?

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Medway Maniac View Drop Down
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Post Options Post Options   Quote Medway Maniac Quote  Post ReplyReply Direct Link To This Post Topic: GPS Tracking - Youth Nats 2013 - Eh?
    Posted: 01 May 13 at 10:14am
Like many of you, I guess, I got the Sailracer Newsletter in my Inbox today. Among the items was an update on GPS tracking with a link to a replay of the 420's Race 13:


After finding the right zoom and acceleration, this was quite fun to watch.  Alton and Wallis initially battled it out then Alton got clear to leave Wallis fighting with Hazeldine.  Then at 55:55, on their way to the final windward mark, Wallis suddenly shears off downwind, apparently giving up.  The other two continue to the w/w mark and proceed down the run, rapidly catching Wallis, who appears to be limping home. Then, as they catch him at 1:02:20, Wallis re-joins racing Hazeldine and sails with them to the finish.

I go to the results, fully expecting a DNF or RAF from Wallis, if not a DSQ under R.2 for interfering with Hazeldine.  But no, Wallis got a 2nd.

Can someone tell me what was going on here?  Wallis' track downwind is uncannily straight as if there's been a glitch in the tracking, but how?

Could Hazeldine (or anyone else, for that matter) have used the GPS data as evidence in a protest or was there a glitch in the tracking, meaning that any GPS tracks have to be viewed with suspicion by protest committees?
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Simon Lovesey View Drop Down
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Post Options Post Options   Quote Simon Lovesey Quote  Post ReplyReply Direct Link To This Post Posted: 01 May 13 at 10:42am
Pleased you enjoyed the tracking,  we are convinced that this technology will help drive interest in sailing,  and certainly the events we have tracked over the last few months we have seen many tens of thousands of viewers.

The tracker data is transmitted using GPRS mobile data,  so we are reliant on the mobile data network,  this means that not all positions get through -  from a scoring perspective the system has some clever algorithms to give estimated positions when data is lost.  We use the positions to create a provisional finishing table and also calculate the overalls.  When the paper sheets eventually arrive from the finish boat we update the scores,  at Largs our provisional scores from the trackers needed very few updates.  

This all means we can do real time scoring,  even doing predications based on mark roundings.  There is also a wealth of data to absorb interest for both the spectator and sailor

Since the RYA Youths more development has been undertaken which will all improve accuracy 
www.sailracer.org
Online Sailing Results, GPS Tracking & Event Management
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transient View Drop Down
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Post Options Post Options   Quote transient Quote  Post ReplyReply Direct Link To This Post Posted: 01 May 13 at 10:43am
Can Albacores do 21 knots?


Looks like a glitch to me....or should I say, a glitch is the most likely explanation.
If they had sailed the course shown by the tracklog they wouldn't need to use the GPS as evidence because there would be no shortage of witnesses. 

edited after Simons post




Edited by transient - 01 May 13 at 10:52am
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Post Options Post Options   Quote transient Quote  Post ReplyReply Direct Link To This Post Posted: 01 May 13 at 10:46am
...PS:

Love these tracked events. Great viewing  Smile
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JimC View Drop Down
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Post Options Post Options   Quote JimC Quote  Post ReplyReply Direct Link To This Post Posted: 01 May 13 at 11:08am
Originally posted by Simon Lovesey

from a scoring perspective the system has some clever algorithms to give estimated positions when data is lost.

Hmm, that seems to make the data useless for anything else unless you have a means to clearly distinguish estimated positions from recorded positions. Of course recorded positions are subject to inaccuracies too, and should really be thought of as a fuzzy blob of uncertainty rather than a single point.
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Post Options Post Options   Quote Simon Lovesey Quote  Post ReplyReply Direct Link To This Post Posted: 01 May 13 at 11:42am
Originally posted by JimC

 
Hmm, that seems to make the data useless for anything else unless you have a means to clearly distinguish estimated positions from recorded positions. Of course recorded positions are subject to inaccuracies too, and should really be thought of as a fuzzy blob of uncertainty rather than a single point.

We are reading the GPS data every 5 seconds,  and estimates are highlighted,  some of the development we are doing is working on making sense of the noisy data.

The point I was trying to make is we can manually correct results as more information is received
www.sailracer.org
Online Sailing Results, GPS Tracking & Event Management
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JimC View Drop Down
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Post Options Post Options   Quote JimC Quote  Post ReplyReply Direct Link To This Post Posted: 01 May 13 at 11:54am
Sure, its not a criticism to say something isn't particularly great for something its not designed to do... Especially if attempting to make it work for the oher task would compromise its usefulness at the primary aim.

I was musing over Maniac's comment about GPS and protest hearings... Its like video evidence: you have to be aware of the limitations rather than take what appears as gospel.
If you take his example of an apparently missed mark rounding then, were that an offshore race with no visual evidence, then you'd need to know which points were real and which ones were calculated.
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Post Options Post Options   Quote pondmonkey Quote  Post ReplyReply Direct Link To This Post Posted: 01 May 13 at 12:09pm
Originally posted by Simon Lovesey

we are convinced that this technology will help drive interest in sailing

is that the 'royal we' Simon?
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Post Options Post Options   Quote GybeFunny Quote  Post ReplyReply Direct Link To This Post Posted: 01 May 13 at 12:19pm
The umpires at the Americas Cup World Series use the the trackers to make calls, there was a youtube clip of an incident floating around. I guess their equipment is bigger, heavier but also more accurate than these sailracer trackers.
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Post Options Post Options   Quote Oli Quote  Post ReplyReply Direct Link To This Post Posted: 01 May 13 at 12:29pm
what id like to see at my club is the tv in the bar hooked up to a computer with live tracking of the racing being shown.  most people have smart phones, there are apps that track and live stream so would just be a case of encouraging people to do it, makes for on the horizon spectating a little more interesting.  maybe not for every race, but certainly for larger all in races and opens.
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