Cocky. if you look at the speeds, they drop to 0 directly after the 33kts, looks like a big crash to me. And the GPS probably had a big dunking at the same time.
Yes I agree the file is a mess, probably because of a very bad sky view.
Select to expand quotedecrepit said..
Well Cocky 2 is correct, that in some circumstances, errors can be picked up without accuracy data, but most of them are eliminated by the processing software's filters. It's the hard ones to spot, like Callan's above where the accuracy data helps.
Well this example is obviously easy to pick apart but I'm still not seeing how Callan's number can be disproved. Everyone is looking at it but I need verification in real simple terms how its not correct. There is no error data provided so all we are doing is assuming. Some on one side of the fence and some on the other.
This is why I ask Ian to explain to me in more details how he derives the result. This might go a long way to helping us understand how errors can be picked up by a device (or software) that doesn't have SDoP error information.
It's the numbers that don't stand out so much which no one checks that could still be problems. Most people simply load the file onto KA72 and upload to GPSTC from there. No checking.
I'm not into all the lingo sorry so need clarity in really simple terms.
Cheers
Marty
Select to expand quoteCocky2 said..
When you untick 'Doppler" there are 2 sec speeds up to 70 Knots and at least 10 over 35kn which tend to mean bad file would it not?
Not necessarily. High speeds in the non-doppler data are quite normal. The speeds are calculated from the difference in position, and are often very high when the GPS looses reception after crashes or in breaks.
That said, it's quite possible that the data in this file are very poor. Two things that can cause this are (1) the armband slipping so the GPS is under the arm, and (2) the GPS "going bad", for example after some water got into it.
So here's a look at the trackpoint data.
Just at the 33kt doppler results, there's also 33kt trackpoint numbers, although there's big disagreements between them either side.
Although it doesn't prove that the 33kts is valid, it makes it more likely. The wild altitude fluctuations have also settled down.
A bit of a coincidence that the 33kts fell in a better part of the data.
Select to expand quoteMartinF2 said..
Well this example is obviously easy to pick apart but I'm still not seeing how Callan's number can be disproved. Everyone is looking at it but I need verification in real simple terms how its not correct.
The answer is simple - it is how the Speed sailors at Sandy Point did it before we got error data.
-> it doesn't look like a crash... it looks like the GPS goofed. Since the data looks wrong, then you cannot trust the device.
-> there are many PB's that were lost due to "we cannot trust this track"...
Just ask Adriano with his mega run on Big Sunday -> he did crash... the start of the run looked good (data wise), then about 5-10 seconds before the crash, it looked wrong -> we couldn't trust those datapoints. So... he lost a massive PB.
I'd call it "tunnel vision". The GPS looses reception in a crash, but tries to extrapolate what's happening. That makes perfect sense when driving through a short tunnel - the car will probably be going the same speed as before, and if it was accelerating going into it, it's likely to keep accelerating, too. It does not make sense when speedsurfing, but GPS chips are made for millions of cars, not for a few thousand speedsurfers.
Just as a matter of interest I had a look at my crash last week.
This is a good file from my GW60, I started tail walking in a gust, tried to control it, but spun out and crashed. So this was a fairly extended affair, I was decelerating, and just subsided into the water when I spun out. It was by no means a sudden stop. But look what happens to the trackpoint data. It's saying 54kts as I surface.
Yes we know the fenix? is accurate most of the time, you don't have to keep trying to prove it to us.
Select to expand quotedecrepit said..
Yes we know the fenix? is accurate most of the time, you don't have to keep trying to prove it to us.
Actually the Garmin is accurate every time.
How can the approved devices give different results and errors every time ?
Select to expand quoteCocky2 said..decrepit said..
Yes we know the fenix? is accurate most of the time, you don't have to keep trying to prove it to us.
Actually the Garmin is accurate every time.
How can the approved devices give different results and errors every time ?
They've on sale at Rebel Cocky, 1/2 price I think we all should get one at this price ??
Select to expand quoteCocky2 said.. Actually the Garmin is accurate every time.
Hmmm, well I guess what you meant to say, was that you've seen no obvious errors yet.
That's a long way from your actual statementSelect to expand quoteHow can the approved devices give different results and errors every time ?
And if you're talking about the ancient Garmins and Canmore, are you making a case for us to phase them out now?
Select to expand quoteBoston! said..
Seems like they are good enough for GPS Speedsurfing! "everyday use"
This seems to be what I am asking for.... Let us use devices without error for everyday use but not records.
I posted a scenario last week where we could post from "other devices", but they could be flagged by anyone who suspected bad data in which case that data would be removed. I can't see a negative to this approach.... can anyone else explain to me if this approach has a negative for any GPSTC users?
Select to expand quotevosadrian said..Boston! said..
Seems like they are good enough for GPS Speedsurfing! "everyday use"
This seems to be what I am asking for.... Let us use devices without error for everyday use but not records.
I posted a scenario last week where we could post from "other devices", but they could be flagged by anyone who suspected bad data in which case that data would be removed. I can't see a negative to this approach.... can anyone else explain to me if this approach has a negative for any GPSTC users?
Last week you posted asking for one simple rule change [ wrt. gps devices ] to allow non-error-producing devices to be used.
The catch is, there is only a single rule for the devices - it must produce error data.
There are no other rules. Every other attribute is a just a setting, eg: 1Hz, battery-saving, etc (so not a rule).
Select to expand quotedecrepit said..Cocky2 said.. Actually the Garmin is accurate every time.
Hmmm, well I guess what you meant to say, was that you've seen no obvious errors yet.
That's a long way from your actual statementHow can the approved devices give different results and errors every time ?
And if you're talking about the ancient Garmins and Canmore, are you making a case for us to phase them out now?
17 000 km of testing does not show any issues Doppler Garmin.
How can you phase out Canmore?
Are you now saying that all the data in the data base for GPSTC is inaccurate for Canmore.
It is a fact that The early 2007 and 2008 data is dodgy as it was trackpoint with SDOP or Error data.
Select to expand quotemathew said..vosadrian said..Boston! said..
Seems like they are good enough for GPS Speedsurfing! "everyday use"
This seems to be what I am asking for.... Let us use devices without error for everyday use but not records.
I posted a scenario last week where we could post from "other devices", but they could be flagged by anyone who suspected bad data in which case that data would be removed. I can't see a negative to this approach.... can anyone else explain to me if this approach has a negative for any GPSTC users?
Last week you posted asking for one simple rule change [ wrt. gps devices ] to allow non-error-producing devices to be used.
The catch is, there is only a single rule for the devices - it must produce error data.
There are no other rules. Every other attribute is a just a setting, eg: 1Hz, battery-saving, etc (so not a rule).
No that is not what I asked for.
Select to expand quotemathew said..vosadrian said..Boston! said..
Seems like they are good enough for GPS Speedsurfing! "everyday use"
This seems to be what I am asking for.... Let us use devices without error for everyday use but not records.
I posted a scenario last week where we could post from "other devices", but they could be flagged by anyone who suspected bad data in which case that data would be removed. I can't see a negative to this approach.... can anyone else explain to me if this approach has a negative for any GPSTC users?
Last week you posted asking for one simple rule change [ wrt. gps devices ] to allow non-error-producing devices to be used.
The catch is, there is only a single rule for the devices - it must produce error data.
There are no other rules. Every other attribute is a just a setting, eg: 1Hz, battery-saving, etc (so not a rule).
The Canmore is approved for use if you read rules.
A while ago, Nigel was sending me comparisons between a GT31 and a fenix for comparisons.
Here's the worst example for the 10s division.
GT31 14:35:40 29.080kts +/-0.537 kts
Fenix 14:35:43 30.253 kts difference 1.173 kts
Yes some of the time they were really close, but this is a larger difference than I've seen between other devices I've looked at.
And the data from the GT31 is also not brilliant, we'd like to see the error data about half that.
Phasing out Canmores and ancient devices no longer complying with latest standards would be easy, we just give enough notice so people can purchase new units. But in my opinion we should wait until at least the motion gps and gyro gps have been approved, so sailors have some choice.
At what point does this thread come under the category of "Flogging a dead horse". I suspect we reached that point early in page 1.
Select to expand quoteJohn340 said..
At what point does this thread come under the category of "Flogging a dead horse". I suspect we reached that point early in page 1.
I guess, it's the same with Petermac's ridiculous threads, for some reason, you just can't leave it alone, even though he refuses to understand.
Select to expand quoteCocky2 said..Cocky2 said.. Actually the Garmin is accurate every time.How can the approved devices give different results and errors every time ?
17 000 km of testing does not show any issues Doppler Garmin.
May I suggest the following:
Homework 1:
Please read and understand bioresonant.com/dl/dl.htm?name=SDOP.pdf
Homework 2:
Please do a 5-hour stationary speed logging test of your GPS and post the doppler speed data - just the mean, standard deviation and maximum speed errors will do.
Note: As this is a stationary test, all non-zero speeds are speed errors.
Homework 3:
If any of the speeds found in Homework 2 are non-zero, then please ask the GPS manufacturer if they would kindly provide an upper bound of speed error for each GPS recorded speed, as this will allow you to automatically check your speed accuracy for each recorded value even when you are not doing a stationary test.
i.e. ask them if they can make the GPS output a SDOP value for each speed value.
Homework 4:
If this is all too hard then please start again at Homework 1.
Select to expand quotedecrepit said..
Phasing out Canmores and ancient devices no longer complying with latest standards would be easy, we just give enough notice so people can purchase new units. But in my opinion we should wait until at least the motion gps and gyro gps have been approved, so sailors have some choice.
You can not phase out Canmore until you have a device that lasts longer than 5 hours battery for distance.
Unlike a privilege few with old GT31 that have not had to deal with GW52 and GW60 issues.
Select to expand quoteTGale said..Cocky2 said..Cocky2 said.. Actually the Garmin is accurate every time.How can the approved devices give different results and errors every time ?
17 000 km of testing does not show any issues Doppler Garmin.
May I suggest the following:
Homework 1:
Please read and understand bioresonant.com/dl/dl.htm?name=SDOP.pdf
Homework 2:
Please do a 5-hour stationary speed logging test of your GPS and post the doppler speed data - just the mean, standard deviation and maximum speed errors will do.
Note: As this is a stationary test, all non-zero speeds are speed errors.
Homework 3:
If any of the speeds found in Homework 2 are non-zero, then please ask the GPS manufacturer if they would kindly provide an upper bound of speed error for each GPS recorded speed, as this will allow you to automatically check your speed accuracy for each recorded value even when you are not doing a stationary test.
i.e. ask them if they can make the GPS output a SDOP value for each speed value.
Homework 4:
If this is all too hard then please start again at Homework 1.
Read this 2007 study for GT11/GT31 A few times.
Do you have this study repeated for GW52?
Do you have this study repeated for GW60
especially as it is worn on the wrist?
Select to expand quotevosadrian said..
This would be so easy to keep everyone happy. There is currently a selection when you enter the data where you can select positional or doppler. This could be added to or changed so that you can select SDOP or no SDOP (even leave is the same, but re define doppler to mean having SDOP and positional to mean not having SDOP). This particular parameter is redundant anyway of people are only permitted to use a Locosys which has doppler by definition.
Then I suggest the following based on that data. Firstly, this is my preference:
* If someone without SDOP posts suspicious data (or even good data that is in the upper echelon of performance so threatening other sailor results) and the data is questioned by anyone (captain or another team member or from another team), the data is removed and the poster of the data has no right of appeal. Simply they cannot prove the data is accurate so it is removed. Move the burden of proof to the sailor to prove their data is good rather than the other way around.
* If nobody has reason to question the data (it makes sense when compared to other parameters like 2S vs 5X10 and is within the realms of the sailors ability and the conditions), it is allowed to stand and contribute to team results.
This is is another option if above is unacceptable:
* People can post without SDOP, but changes are made to the inner workings of the GPSTC so that data without SDOP cannot contribute to team or individual result rankings. The data is in the users database but has not other effect on anyone else. It appears in the session results and other team members can comment and encourage. The benefit of this option above posting in the comments is that the user can still keep their own PB lists including kms sailed, and all PBs for their own benefit, but it does not effect anyone else. If the user finds themselves getting good results and the team encourages them to put up real data that can contribute to team results, they may then be encouraged to fork out the $$$ on an approved device so they can contribute.
Both of the above options will cause no issue for competitive sailors who are concerned about other sailors/teams getting a competitive advantage due to bad data. In one option the data does not count ever. In the other, data can be flagged and removed if it is causing a competitive issue.
The benefits of both options are that they are INCLUSIVE which is what the GPSTC claim is their philosophy. These changes will attract new sailors who are currently interested but not wanting to buy another expensive device, and the inclusion may encourage them to buy the correct device later because they enjoy it. This will also allow existing members who are not competitive and do not wish to buy an approved device that they do not like to continue to be included without rocking the boat of those who are competitive. I just can't see a negative to this approach other than a small amount of work to implement it.
It would seem my suggestions here must make too much sense since nobody can point out how it would negatively impact anyone.
Both of these approaches allow sailors with non-SDOP devices to log sessions without causing competitive concern to those using SDOP approved devices and competing for team/individual position.
Select to expand quoteCocky2 said..
Read this 2007 study for GT11/GT31 A few times.
Do you have this study repeated for GW52?
Do you have this study repeated for GW60
especially as it is worn on the wrist?
Good work, seems the reading part of Homework 1 is progressing well. Hint: The understanding part may need you to consider broader implications for devices and situations such as those you mention. Yes, you can work together with your friends (eg decrepit, Sailquik) if you like.
Select to expand quoteTGale said..Cocky2 said..
Read this 2007 study for GT11/GT31 A few times.
Do you have this study repeated for GW52?
Do you have this study repeated for GW60
especially as it is worn on the wrist?
Good work, seems the reading part of Homework 1 is progressing well. Hint: The understanding part may need you to consider broader implications for devices and situations such as those you mention. Yes, you can work together with your friends (eg decrepit, Sailquik) if you like.
No you can not work with the non inclusive committee as unlike GPSs they will not allow any device without SDOP and error values.
You have not answered the questions below as to how these devices were tested to these standards.
Do you have this study repeated for GW52?
Do you have this study repeated for GW60
especially as it is worn on the wrist?
^^^^^
I believe the committee have already completed this assignment (including Homework 2 for the devices you mention), and I'm sure they will provide advice on how to test your own device if you are unsure. It would be appreciated if you could provide your own answers to Homework 2, we would be interested to see how small the errors might be.
Hint 2: If you find you are procrastinating by repetitively asking others for the answers, then you may like to
a) reflect more deeply on the previously provided answers, and
b) collaborate with classmates - working alone rarely works out well, especially in small classes such as ours.
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Seriously, though, suggestions from yourself and the likes of vosadrian seem insightful from the point of view of capturing the mood of part of the class in regard to an alternative route to Homework 3 suitable for the less-technically obsessed. It seems the committee is reticent to go there again, they appear glad to be free of the non-SDOP days and the tedium of manually checking GPS results. What the committee will no doubt be seriously considering, though, is can we afford not to go there? Should a "non-approved" device category be added to GPS Team Challenge? There is much to be said for the ease of use and robustness of mainstream products and the diversity of devices and sailors that these appeal to. The obvious downside is that it needs to be designed and the programming done. And it will cause a change - at a certain age we get more resistant to change, even change for the better!!
