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vosadrian said..

firiebob said..
vosadrian if you don't mind me asking, what team are you in and what name do you go by there.
Cheers Bob

gpsteamchallenge.com.au/sailor/view/561

Thanks Adrian

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Kazza said..
Just for interest sake (probably been discussed before) has anyone worn an approved device & an unapproved device for a session and compared results?? Is there a difference And if so which one is faster
I noticed my GW60 had faster results than the GT31 and they're both approved.

Kazza I don't own an unaproved device so can't answer that, but I have sailed with the GT31 and other devices. And your observation is typical. The accepted theory, is that later devices are set to a higher frequency, ir GT31 is 1 sample per second. the recommended aquistition rate for the GW60 is 5 samples per second. This allows the analysing software to more closely centre on the peak speed, whereas at 1 sample per second on a 2s result the peak could be off to the side. I've also noticed a difference between devices worn on my head and my upper arm, typically the device on my head has better accuracy and a slightly higher reading.
So there is enough variation between trusted devices, without adding other imponderable factors into the mix.

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mathew said..
If people dont want to have a level playing field, then fine.... lets allow any device.

Other people with the ability to build their own gps, will do so... and they will be allowed to make those devices report higher numbers than everyone else.

My plan is, Mathew, as soon as Gpstc relents and allows all kinds of GPS devices to be registered on whatever tiered system I'm gonna buy four or five of these things off ebay and then pick whichever one is fastest to post with....... Oh, I forgot, that would only be OK for you and a "level playing field" if said devices were "GPSTC compliant"

I vote for Red !! president of GPSTC !!!!

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seanhogan said..
I vote for Red !! president of GPSTC !!!!

2nd Red! The voice of reasonable!!!

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decrepit said..
The accepted theory, is that later devices are set to a higher frequency, ir GT31 is 1 sample per second. the recommended aquistition rate for the GW60 is 5 samples per second. This allows the analysing software to more closely centre on the peak speed, whereas at 1 sample per second on a 2s result the peak could be off to the side.

This is a theory that's "widely" believed but actually wrong. Speed does not vary nearly as quickly as random error, which tends to be around 0.5 knots. The software centers peaks around noise, not actual speed. Here's an example from the first pair of files I pulled up where the 2-second region between 2 devices differs by 0.4 seconds:




You should be able to find examples in your data if you look at your comparisons where you had devices very close to each other. You'd find plenty of examples where the regions are offset by 0.2 seconds or more.

A definitive advantage that higher-rate data have is that the net effect of random error on results is smaller, so the accuracy is higher, simply because each point contributes less to the results - for 5 Hz data, one fifths. For devices that are worn on different parts of the body, data have shown that the accuracy can be good enough to measure actual speed differences from body parts moving differently - for example from head movements.

I have a GW-60 and really like it.

When I don't need gpst-level accuracy, or even need to upload, I use a cheap ($70 USA) Timex Ironman GPS. This Timex has ONLY gps. None of the fitness stuff, like heartbeat and steps, etc. The charger cable is micro-usb, no special stuff. It uploads to a Timex cloud app and can upload to Strava and other such sites. No wifi or BT. This thing is simple and simple to operate on the water. Battery in gps mode goes about 6 hours. Easy to record, store, view on the watch, and upload multiple sessions.

When I have worn both the GW-60 and the Timex together on the same arm, the results are very close to each other.

Good enough, and only $70 if I kill it. Not approved for official results, but I don't need it to be.

Hi Red well said.
As to the small minority of people that want change,I think the point is that like most of them I'm all for the accuracy side of things. But unfortunately we don't have easy access to approved devices.
Feel free to correct me if I'm wrong but currently we have the following.
1 gw60 watch (great device by the way right up until the band brakes and you loose it or the buttons stop working)
2 motion device -more expensive but looks like a great device. (not easily available and has a long waiting list.
3 canmore which I read above is going to be phased out at end of the year.
One point on the above thanks for the work developing the motion julienne I'm sure in time list will go away and they will be more available.
In regards to other watches there are people who have been using other brands for years with no issues that are similar cost to the gw60 and they don't have the button issues and band issues that seem to be associated with the gw60.
I would also ask why the secrecy around the advisory committee. It seems that Kato is the only one who has put his hand up in that regard. I would also ask what was the process for choosing that committee.?
I have been involved in gpstc for a few years now and love being able to see and compare my results with others but if I can't get an approved device then this will come to an end,
Perhaps we should have a vote proposed to all members that are currently registered with gpstc and get some data from the members. and not just speculation from the "small minority" or gpstc dictatorship as to whether a proposal of a 2 tier system is wanted.
This would then put an end to the speculation that seems to thrown around on the forum.
It would be very easy to set up an online transparent voting system.

Secrecy around the advisory committee?

The following is a direct quote from the About tab on the GPSTC website.

"There is an advisory group to make decisions on the day to day running of the challenge made up of sailors from a number of states. Membership of the group is open to all. Contact us if you wish to be a part or have any queries."

Membership open to all! Where is the gun in that? I was hoping for secret handshakes.

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John340 said..
Secrecy around the advisory committee?

The following is a direct quote from the About tab on the GPSTC website.

"There is an advisory group to make decisions on the day to day running of the challenge made up of sailors from a number of states. Membership of the group is open to all. Contact us if you wish to be a part or have any queries."

Membership open to all! Where is the gun in that? I was hoping for secret handshakes.

Is privacy the same as secrecy? It is a volunteer group, open to all. The GPSTC is a privately owned web based database. The advisory committee advises. The rules of the GPSTC are are published and we'll know. The reasons behind the rules have been canvassed multiple times in this forum.

I have a heavy democratic thread running through me, but I'm getting disillusioned.
Democracy can only work well when the people involved are on top of the real facts. There's to much fake facts and rejection of science and logic at the moment, for democracy to deliver the best outcomes.

The GPSTC was never a democracy, Hardy's great idea was developed by interested parties at the time, and implemented by Nebs.

Hardy and Nebs then looked after the site for many years, until burnout and heavy personal commitments, led to responsibilities being diversified. But Nebs still has sole access to the database and bank account. Nothing major can change without him being heavily involved. And at the moment he's flat out with his own life.
Take it from me, what we have is what we've got, no amount of wishing and writing stuff here is likely to change that.

And yes, I thought it would be obvious, I'm also part of the advisory group. But revealing peoples identities without their permission is not something I'm comfortable with

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boardsurfr said..
>>
This is a theory that's "widely" believed but actually wrong. Speed does not vary nearly as quickly as random error, which tends to be around 0.5 knots. The software centers peaks around noise, not actual speed. Here's an example from the first pair of files I pulled up where the 2-second region between 2 devices differs by 0.4 seconds:




You should be able to find examples in your data if you look at your comparisons where you had devices very close to each other. You'd find plenty of examples where the regions are offset by 0.2 seconds or more.

A definitive advantage that higher-rate data have is that the net effect of random error on results is smaller, so the accuracy is higher, simply because each point contributes less to the results - for 5 Hz data, one fifths. For devices that are worn on different parts of the body, data have shown that the accuracy can be good enough to measure actual speed differences from body parts moving differently - for example from head movements.

Thanks Peter. I was looking for the 10hz comparison I did with the motion and V3 on my head. From memory they were much closer than your example, I thought at the time this implied the wave form may not be just random noise.
I'll keep looking for it, I hope this old brain hasn't got to the stage it's remembering stuff that didn't happen. Forgetting stuff that did happen is bad enough!

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Bugs74 said..>>>>>
Feel free to correct me if I'm wrong but currently we have the following.
1 gw60 watch (great device by the way right up until the band brakes and you loose it or the buttons stop working)
2 motion device -more expensive but looks like a great device. (not easily available and has a long waiting list.
3 canmore which I read above is going to be phased out at end of the year.
One point on the above thanks for the work developing the motion julienne I'm sure in time list will go away and they will be more available.
In regards to other watches there are people who have been using other brands for years with no issues that are similar cost to the gw60 and they don't have the button issues and band issues that seem to be associated with the gw60.
I would also ask why the secrecy around the advisory committee. It seems that Kato is the only one who has put his hand up in that regard. I would also ask what was the process for choosing that committee.?
I have been involved in gpstc for a few years now and love being able to see and compare my results with others but if I can't get an approved device then this will come to an end,
Perhaps we should have a vote proposed to all members that are currently registered with gpstc and get some data from the members. and not just speculation from the "small minority" or gpstc dictatorship as to whether a proposal of a 2 tier system is wanted.
This would then put an end to the speculation that seems to thrown around on the forum.
It would be very easy to set up an online transparent voting system.

Well there is one more option. you can make your own logger.

I've made two of them, a 5hz version and a 10hz capable version. Mine are more complicated than necessary, because I wanted to be able to adjust settings while experimenting with them.
You only need the gps chip, a logger, switch, battery, it's charger and an enclosure. and of course wire, and soldering skills.

I'm more than happy to help, if anybody's keen.

Also Julien has said he may also make a basic logger.
That way you can use anything you want for on water feed back and post with an approved device.

I think that was my point. It's not a democracy so we either as decrepit says take what is on offer or we leave. So inclusive once again.

Given I started this mess, I suppose I should make my opinion known.

Upon deep reflection, I realize that If we could ban humans from the GPSTC then all these problems would be resolved, and admit that my biggest flaw in developing the GPSTC was that I allowed humans to join, and therefore I think this disqualifies me from any labels such as Genius

But given we have humans involved, I see 2 issues.

1. Inclusiveness
2. Data Integrity

These 2 will naturally come into conflict.

Without Data Integirty, the recording of speeds, and the rankings among sailors are meaningless, so you have to have it. Regarding Inclusiveness, if it's not too big a task, some way of tagging Recreational Sailing with non-integrity devices, which will have no bearing on team scores, or rankings, is a possible solution to allow others to participate in the GPSTC. You either have data integrity or you don't, without it there's not a lot of meaning to posting and comparing gps data. You've got to have boundaries in life, and this is one of them, so if you want to appear in the Rankings, and contribute to team scores in the GPSTC, then there has to be data integrity with/from approved gps devices.

In regards to data integrity, the theory from statistics in relation to sensitivity and specificity explains why we need data integrity:

Sensitivity and specificity are statistical measures of the performance of a binary (True or False) classification test, also known in statistics as a classification function:

Sensitivity (also called the true positive rate, the recall, or probability of detection measures the proportion of actual positives that are correctly identified as in our measures of windsurfing speed in knots, (e.g., the percentage of windsurfers who are correctly identified as having reached 20kts, 25kts, 30kts, 35kts, 40kts, 45kts 50kts.

Specificity (also called the true negative rate) measures the proportion of actual negatives that are correctly identified as such (e.g., the percentage windsurfers who have not reached a certain Speed, Your GPS reads 29kts, and in reality you have not reached 30kts, eg not many windsurfers in the GPSTC have reached 50kts.

In order to achieve a true positive in our case, we require GPS devices which are regarded as having a high accuracy rate, as has been previously discussed on this topic.

Sensitivity therefore quantifies the avoidance of false negatives (when someone has reached 30kts but the device only shows 29kts) and Specificity does the same for false positives (That someone who has only reached 29kts does not record 30kts) .

The issue here is what trade off do we want. There is usually a trade-off between the measures - for instance, in airport security, since testing of passengers is for potential threats to safety, scanners may be set to trigger alarms on low-risk items like belt buckles and keys (low specificity) in order to increase the probability of identifying dangerous objects and minimize the risk of missing objects that do pose a threat (high sensitivity).

Our trade off is inclusiveness vs data integrity.

In our case if we want to include more participants in the GPSTC (Increase Inclusiveness) and allow all GPS devices even those with low sensitivity and larger error rates (GPS devices with low accuracy), we may have more readings of people doing 30kts when in actual fact they are only doing 29kts. This affects the integrity of the data, and then does not accurately detect how difficult is is to do 30kts, and detect accurately how many people are capable of sailing at 30kts. We end up with low data Integrity. If We aim for super high sensitivty, and were to say only NASA approved GPS devices that cost $10,000 that achieve an accuracy with 0.0001 of a knot, then we would end up with the highest possible data integirty, at the cost of inclusiveness as most people would drop out of the GPSTC. I think we have the balance between sensitivity and specificity about right.

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hardie said..
In regards to data integrity, the theory from statistics in relation to sensitivity and specificity explains why we need data integrity:

Sensitivity and specificity are statistical measures of the performance of a binary (True or False) classification test, also known in statistics as a classification function:

Sensitivity (also called the true positive rate, the recall, or probability of detection measures the proportion of actual positives that are correctly identified as in our measures of windsurfing speed in knots, (e.g., the percentage of windsurfers who are correctly identified as having reached 20kts, 25kts, 30kts, 35kts, 40kts, 45kts 50kts.

Specificity (also called the true negative rate) measures the proportion of actual negatives that are correctly identified as such (e.g., the percentage windsurfers who have not reached a certain Speed, Your GPS reads 29kts, and in reality you have not reached 30kts, eg not many windsurfers in the GPSTC have reached 50kts.

In order to achieve a true positive in our case, we require GPS devices which are regarded as having a high accuracy rate, as has been previously discussed on this topic.

Sensitivity therefore quantifies the avoidance of false negatives (when someone has reached 30kts but the device only shows 29kts) and Specificity does the same for false positives (That someone who has only reached 29kts does not record 30kts) .

The issue here is what trade off do we want. There is usually a trade-off between the measures - for instance, in airport security, since testing of passengers is for potential threats to safety, scanners may be set to trigger alarms on low-risk items like belt buckles and keys (low specificity) in order to increase the probability of identifying dangerous objects and minimize the risk of missing objects that do pose a threat (high sensitivity).

Our trade off is inclusiveness vs data integrity.

In our case if we want to include more participants in the GPSTC (Increase Inclusiveness) and allow all GPS devices even those with low sensitivity and larger error rates (GPS devices with low accuracy), we may have more readings of people doing 30kts when in actual fact they are only doing 29kts. This affects the integrity of the data, and then does not accurately detect how difficult is is to do 30kts, and detect accurately how many people are capable of sailing at 30kts. We end up with low data Integrity. If We aim for super high sensitivty, and were to say only NASA approved GPS devices that cost $10,000 that achieve an accuracy with 0.0001 of a knot, then we would end up with the highest possible data integirty, at the cost of inclusiveness as most people would drop out of the GPSTC. I think we have the balance between sensitivity and specificity about right.

No doubt about it, thems be da words of a Genuis!

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fangman said..

hardie said..
In regards to data integrity, the theory from statistics in relation to sensitivity and specificity explains why we need data integrity:

Sensitivity and specificity are statistical measures of the performance of a binary (True or False) classification test, also known in statistics as a classification function:

Sensitivity (also called the true positive rate, the recall, or probability of detection measures the proportion of actual positives that are correctly identified as in our measures of windsurfing speed in knots, (e.g., the percentage of windsurfers who are correctly identified as having reached 20kts, 25kts, 30kts, 35kts, 40kts, 45kts 50kts.

Specificity (also called the true negative rate) measures the proportion of actual negatives that are correctly identified as such (e.g., the percentage windsurfers who have not reached a certain Speed, Your GPS reads 29kts, and in reality you have not reached 30kts, eg not many windsurfers in the GPSTC have reached 50kts.

In order to achieve a true positive in our case, we require GPS devices which are regarded as having a high accuracy rate, as has been previously discussed on this topic.

Sensitivity therefore quantifies the avoidance of false negatives (when someone has reached 30kts but the device only shows 29kts) and Specificity does the same for false positives (That someone who has only reached 29kts does not record 30kts) .

The issue here is what trade off do we want. There is usually a trade-off between the measures - for instance, in airport security, since testing of passengers is for potential threats to safety, scanners may be set to trigger alarms on low-risk items like belt buckles and keys (low specificity) in order to increase the probability of identifying dangerous objects and minimize the risk of missing objects that do pose a threat (high sensitivity).

Our trade off is inclusiveness vs data integrity.

In our case if we want to include more participants in the GPSTC (Increase Inclusiveness) and allow all GPS devices even those with low sensitivity and larger error rates (GPS devices with low accuracy), we may have more readings of people doing 30kts when in actual fact they are only doing 29kts. This affects the integrity of the data, and then does not accurately detect how difficult is is to do 30kts, and detect accurately how many people are capable of sailing at 30kts. We end up with low data Integrity. If We aim for super high sensitivty, and were to say only NASA approved GPS devices that cost $10,000 that achieve an accuracy with 0.0001 of a knot, then we would end up with the highest possible data integirty, at the cost of inclusiveness as most people would drop out of the GPSTC. I think we have the balance between sensitivity and specificity about right.

No doubt about it, thems be da words of a Genuis!

Them's sure are Ross, but also, I fear it won't be the last word. Thank you Hard One, for your strong leadership and ideals.

Peter, I found it, It wasn't a windsurfing test, it was on top of the wagon, V3 and motion side by side, this is a low speed 10s.


There is very little evidence of (noise) here, unless it's affecting both units equally. whereas when I'm sailing the wave form is no where near as smooth. I have a feeling some of the stuff is real, maybe chop induced.

So next time out, I'll have both 10hz units in my helmet.

Thanks Hardie, I am as always a great admirer of your work. And yes humans are the problem

Well said, Hardie.

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Bugs74 said..
Perhaps we should have a vote proposed to all members that are currently registered with gpstc and get some data from the members. and not just speculation from the "small minority" or gpstc dictatorship as to whether a proposal of a 2 tier system is wanted.
This would then put an end to the speculation that seems to thrown around on the forum.
It would be very easy to set up an online transparent voting system.

I just saw this. I put together a quick poll but it looks like I cannot post a link here. I'll have to look at other options.

If there's anyone out there who has strong feelings about this, please feel free to fill it out. It's not in any way associated with the GPSTC leadership. If you guys find it useful, feel free to post a link in a separate post, or where ever. I'll share responses here (if there are any).

I get asked about GPS devices on a regular basis - from current GPSTC team members, potential new recruits, and other windsurfers who just want to record their sessions. Manyhave a very strong preference towards a wrist watch over an armband-type device like the Motion. But unless they are already somewhat serious speedsurfers, I am hesitant to recommend the GW-60, given the many issues it has had in the past. I am often looking for cheaper alternatives to record my "slow" sessions, since the GW60 has a somewhat limited life expectancy. The buttons on my GW60 again started acting up, and last time I opened the watch and cleaned them, corrosion had eaten quite a bit of the little metal strips. So despite having about 10 approved GPS devices, I'd still love the option to post non-counting sessions from a cheap Timex or similar watch. I know others in our team think the same way.

It's worth pointing out that one of the reasons to allow "recreational" postings from non-approved devices is to attract potential new members. Having to spend several hundred dollars for an approved device is a definitive hurdle, especially for someone who is just starting out and does not really have a chance to collect jelly beans, anyway. Sure, some people won't think twice about it, but itisan issue for others, for example youngsters. Just asking current GPSTC member is likely to produce a skewed result, since anyone in the GPSTC has (or at least has had) an approved device already.

I put screenshots and a link to the poll in a blog post at boardsurfr.blogspot.com/2019/09/gps-team-challenge-device-poll.html
Filling it out should take just a minute.

I'm planning on posting poll results here and on my blog. A couple of screen shots of the questions:

I would like to extend gratitude to those who are behind the scenes of the GPSTC. Great idea and great format.
That said this debate around accuracy seems fairly arbitrary to me. At the end of the day if you are not sailing at exactly the same time, at the same location with the same equipment you really are comparing apples oranges (which is what the GPSTC does).
I love(d) the GPSTC for my own personal comparisons, yet others seemed to think they could gauge their abilities and testicular fortitude by comparing their numbers to other competitors. Maybe I'm wrong but comparing different sailors numbers seems stupid.

If you really want to make the competition "fairer" reward improvements as well.

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Belly25 said.. >> If you really want to make the competition "fairer" reward improvements as well.

That's what Pbs are about, you normally get congratulations from all sorts of people.

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decrepit said..

Belly25 said.. >> If you really want to make the competition "fairer" reward improvements as well.

That's what Pbs are about, you normally get congratulations from all sorts of people.

There's a bit of the hidden genius in the GPSTC design in the PBs. Some people are more accomplishment oriented, others are more people oriented. The first group may mostly appreciate the improvements for what they are; the second group may mostly appreciate the congratulations; but most people will appreciate both at least somewhat. Designing a system like the GPSTC that can keep people with very different motivations happy is a stroke of genius.