Thought it might help if we post up some examples of GPS posts that are seriously erroneous and, of course, from 'non GPSTC approved' GPS's.

Here is the latest:

www.ka72.com/Track/t/435170

It is assumed this is a windsurfer, but it may not be. In any case, even if it was a kite or a foiler, doing thise speeds on a beam reach in open water is extremely unlikely, let alone 49 knots!

And of course, there is no way to validate anything.

See it all the time on Ka, almost always with Garmin or devices I don't recognise, haven't seen it filter through to GPSTC. I am sure those who could be bothered would be on it like flies if it did

a little gust...

g'day, how is it assumed it is a windsurfer ?
could be the latest secret Slovenian stealth jet ski as far as...

has it been posted on gpstc to disturb the gps world order ?

Anyone asked for it to be validated ?

Sorry Sailquik, I have a lot of respect for your work , but this topic is rather useless, as Mr keen pointed out it happens all the time on ka72, and so what ?
Ka72 has no pretention to validate world records or team rankings, so until everyone is happy to buy a motion/ logger ....let's leave it that way and let those who post check their results and modify then if needed.... or not.

sean

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powersloshin said..
a little gust...

Followed by a solid catapult...

Sailquick I am not sure "how this helps" , no way of telling which model Garmin product it is , if the point is to say Garmins are inaccurate. I've seen some shocking tracks of approved devices like the canmore or any device that is worn in a way that hampers the signal. I think alot of sailors are happy with the release of the motion and wearing some other device to give them on water feedback.

Simon, I don't think there is any wind at Sandy Point, again.

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seanhogan said..
g'day, how is it assumed it is a windsurfer ?
could be the latest secret Slovenian stealth jet ski as far as...

has it been posted on gpstc to disturb the gps world order ?

Anyone asked for it to be validated ?

Sorry Sailquik, I have a lot of respect for your work , but this topic is rather useless, as Mr keen pointed out it happens all the time on ka72, and so what ?
Ka72 has no pretention to validate world records or team rankings, so until everyone is happy to buy a motion/ logger ....let's leave it that way and let those who post check their results and modify then if needed.... or not.

sean

Wait till I post this one:

now you're talking ! (hope it was foiling !)

So Sailquik, Are you implying that approved devices do not make serious errors? That these type of errors can only happen on non-approved devices?

And another question.... since these errors are so obvious, is it not simple to just flag them as errors and move on?

I think. Andrew's point is, that there is no accuracy data to check what happened. Yes any device can produce this sort of error, but if there's satellite info and SDoP numbers, the likelihood of error can be estimated.
And yes anything can be posted on KA72, that's why I don't like it being the default gateway to the GPSTC.

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decrepit said..
I think. Andrew's point is, that there is no accuracy data to check what happened. Yes any device can produce this sort of error, but if there's satellite info and SDoP numbers, the likelihood of error can be estimated.
And yes anything can be posted on KA72, that's why I don't like it being the default gateway to the GPSTC.

for sure Decrepit ! like he's been saying (rightly for GPSTC !) for ever and ever ... just pointing out how not helpful and totally pointless his thread is actually.

Some people may not enjoy ka72, but they should keep from criticizing openly, nobody forces them to use it nor to post to gpstc through it, do they ?

Doesn't gpstc have an UPLOAD funtion ? (haven't been there in years, can't say)
If it hasn't, maybe it's time for it to upgrade and offer the same functionnalities as KA72 (upload/saved personnal data/ export to google earth/download files from other riders = check accuracy ! )

Dylan does an awesome job, is bloody helpful, and it's HIS website, he would be silly to ask riders from all over the globe to only post from devices approved by another website !

my file from a canmore, no big deal.... when I saw it was all f???ed up I changed it from public to private in "my data" easy peasy !

Sean, I asked the same in March this year, and to Andrew's credit, he took the time to explain the reasons GPSTC didn't have an attached program for posting through. A long and detailed explanation but one which did answer my queries. Go to last part of page 1.
Cheers. www.seabreeze.com.au/forums/Windsurfing/Gps/KA72-required-for-GPSTC?page=1

Sean, I have hit a nerve haven't I?

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seanhogan said..
Some people may not enjoy ka72, but they should keep from criticizing openly, nobody forces them to use it nor to post to gpstc through it, do they ?

I admit Dylan has done a great job, it's not KA72 I'm criticising. But I have heard people say, "it was posted on KA72, so it must be right". And there have been team captains, that make it compulsory to post via KA72. It's this attitude that irks me.

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Doesn't gpstc have an UPLOAD funtion ?

This would be awesome, and I'd love for it to happen, maybe in the next decade.

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(upload/saved personnal data/ export to google earth/download files from other riders = check accuracy ! )

I'm afraid we'll have to disagree on that one, it will pick up the obvious bad glitch, if people do check. But that's not my idea of accuracy.

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Dylan does an awesome job, is bloody helpful, and it's HIS website, he would be silly to ask riders from all over the globe to only post from devices approved by another website !

No argument there at all.

I guess I'm just an accuracy nut, and have to realise I'm in a minority and should keep my big mouth shut.

No, accuracy matters. What sets the locosys and Julien's units apart is the fact that they actually REPORT accuracy for us to see and analyze. Other units might be just as accurate, but we can't know that since they don't report. (Some do, but GPSTC goes through a lot of time and effort making sure that the approved devices do the job for "official" records.)

My Timex Ironman GPS seems to be just as accurate as my GW-60, but I can't prove that since it does not report accuracy numbers. For my non-official-speed-recording purposes, it is plenty.

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decrepit said..
Sean, I have hit a nerve haven't I?

It's this attitude that irks me. !! hahahah No you haven't cause I know you're a top helpful guy ! And you always try to round square edges (even when good old Daffy gets on his high horses don't you ?)

(upload/saved personnal data/ export to google earth/download files from other riders = check accuracy ! )
I'm afraid we'll have to disagree on that one, it will pick up the obvious bad glitch, if people do check. But that's not my idea of accuracy. = if you have access to the file like on ka72 (downloadable) , don't you have access to all the bits and pieces of sopdop/etc ?? that would mean you can check the accuracy, don't you ?

I guess I'm just an accuracy nut, and have to realise I'm in a minority and should keep my big mouth shut.
Not at all ! me just thinks accuracy is better discussed over gpstc topics rather than random ka72 files posted from random guy in slovenia with whatever random equipement
no worries Decrepit, all in good fun !

By the same token, whats the point of posting something thats clearly wrong?
If its not goimg to GPSTC then not really a problem unless it effects that areas results ie Kingdoms etc in KA72.

Was this an Annon posting? Again why post annon tracks in the first placeas, the info is lost to Mr Annon and not your own personal records.

KA72 is awesome as anyone can decipher their data but if an Annon posting wasnt allowd (must log in to see results) then it may be less likely for tracks this way out to be posted.

Would also be cool to have a tool on KA72 to be able to cut out areas (mainly thinking of car tracks home) , say on the overlay where you can see the tracks play out.

I am a paid up participant of KA72 & Dylan is doing great at providing this for us.Thanks D

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seanhogan said..

if you have access to the file like on ka72 (downloadable) , don't you have access to all the bits and pieces of sopdop/etc ?? that would mean you can check the accuracy, don't you ?
>>>

Only if those files carry that data, Daffy is talking about files that don't.
If the file has no accuracy data, we can't check it!
And nobody has the time to go through all the posts and check each for a 2 to 5kt discrepancy anyway.

What would be good is if sailors check their own data for accuracy.
With a program like GPSSpeedreader. You can do an upload to the GPSTC, produce a much nicer track overlay on GE with divisions and speed colouring. Also the accuracy data is shown as a line graph, if a spike coincides to a good number you know it's suspect, if the spike is too big, the filters will disallow it.
Because KA72 caters for all sorts of units, it's filters are quite soft, so can let through errors in the knots range, and I see no evidence that SDoP is used in the filters.

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seanhogan said..
my file from a canmore, no big deal.... when I saw it was all f???ed up I changed it from public to private in "my data" easy peasy !

Looks legit for me...

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seanhogan said..
g'day, how is it assumed it is a windsurfer ?

Well, it was posted in the "Windurfer' section.

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seanhogan said..
could be the latest secret Slovenian stealth jet ski as far as...

It could well be. But it was posted as 'windsurfing'.

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seanhogan said..
has it been posted on gpstc to disturb the gps world order ?

Nope, and that was not the point of this thread at all. It is purely to point out that we regularly see some ridiculous errors in GPS data and most, but by no means all, are from non approved devices. As decrepit pointed out. There is no way to pick up less obvious errors of, say 2-3 knots, in a lot of GPS devices. We have examples of a few, but that is only because we also have side by side data from at least one GPSTC approved device for that session.

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seanhogan said..
Anyone asked for it to be validated ?

Nope, and again that is NOT the point.

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seanhogan said..
Sorry Sailquik, I have a lot of respect for your work , but this topic is rather useless, as Mr keen pointed out it happens all the time on ka72, and so what ?

Thank you Sean.
If you find it useless, that is entirely your perogative, and you have every right to simply ignore this thread as you like. But, I have been asked many times, and in many different ways "how wrong can GPS's be"? or similar types of questions. So I thought it would be instructive, and may surprise and amuse some, to post up some of the clangers we come across.

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seanhogan said..
Ka72 has no pretention to validate world records or team rankings, so until everyone is happy to buy a motion/ logger ....let's leave it that way and let those who post check their results and modify then if needed.... or not.

This post was not in ANY WAY about KA72 at all. What was it about the original post that would prompt you to jump to such a strange conclusion?

And, but the way. GPSTC does not validate 'Records'. No idea why that silly chestnut keeps coming up

I actually have a file full of such clangers. Many were never posted on KA71. The fact that I used this image to illustrate the point is not a critisism of KA72 at all and that was certainly not my intention. KA72 is a fantastic resourse for a great many people and that is how it should be. I could have used a screen shot from any one of 5 different GPS file analysers, and that would also be no reflection of those programs either, just the file itself.

But it does makes me wonder "what were they thinking" when I see a post like this. Did the poster really believe that they had that good a day?

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segler said..
No, accuracy matters. What sets the locosys and Julien's units apart is the fact that they actually REPORT accuracy for us to see and analyze. Other units might be just as accurate, but we can't know that since they don't report. (Some do, but GPSTC goes through a lot of time and effort making sure that the approved devices do the job for "official" records.)

My Timex Ironman GPS seems to be just as accurate as my GW-60, but I can't prove that since it does not report accuracy numbers. For my non-official-speed-recording purposes, it is plenty.

GPSTC approved devices would most likely pass the standards for " Official Records", but, GPSTC does not ratify "official records".

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bc said..
Sailquick I am not sure "how this helps" , no way of telling which model Garmin product it is , if the point is to say Garmins are inaccurate. I've seen some shocking tracks of approved devices like the canmore or any device that is worn in a way that hampers the signal. I think alot of sailors are happy with the release of the motion and wearing some other device to give them on water feedback.

I guess you missed the point of the post. It was just to show some extreme examples of GPS error clangers.

I am not saying 'Garmins are inaccurate'. We only have some anecdotal evidence, and a few verified examples, to show that they can be really wrong sometimes. We also have evidence to show that most of the GPSTC approved devices can also be wrong sometimes, but in those cases (as we have stated many times before ) we also have the evidence to know and verify it was wrong.

Of course, I fully agree that various models of GPS sports watches, including the many Garmin varieties, are perfectly fine for on the water 'feedback'.

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vosadrian said..
So Sailquik, Are you implying that approved devices do not make serious errors? That these type of errors can only happen on non-approved devices?

LOL, I was betting you you pop up here again.

The answer is NO! But they probably do happen less often on the better ones. Although it is early days as far as the ammount of data we have, I have not seen any serious errors on Motions yet.

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vosadrian said..
And another question.... since these errors are so obvious, is it not simple to just flag them as errors and move on?

Yes. Of course, with the really obvius ones. But what is your point.... What does "move on' entail

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seanhogan said..
when good old Daffy gets on his high horses.
[/b]

Yep, I am old.

And you know: The older I get, the better I was!

But I gave up riding horses many. many years ago. Too dangerous. Bad enough doing something adventurous with one brain to coordinate. Two brains is a whole other world of potential disaster - i still have the scars to prove it.

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seanhogan said..
my file from a canmore, no big deal.... when I saw it was all f???ed up I changed it from public to private in "my data" easy peasy !

Very easy to spot the errors here BUT if it was only a couple of Knots would you have noticed?

It would have simply sail through as another great day on the water Easy Peasy

No way for anyone to verify right or wrong, that is the point!

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sailquik said..

vosadrian said..
So Sailquik, Are you implying that approved devices do not make serious errors? That these type of errors can only happen on non-approved devices?

LOL, I was betting you you pop up here again.

The answer is NO! But they probably do happen less often on the better ones. Although it is early days as far as the ammount of data we have, I have not seen any serious errors on Motions yet.

vosadrian said..
And another question.... since these errors are so obvious, is it not simple to just flag them as errors and move on?

Yes. Of course, with the really obvius ones. But what is your point.... What does "move on' entail

Will you did actually say "of course, from 'non GPSTC approved' GPS's". I took that to imply that this could only happen from a non-approved device. I assume you were fishing for a query like mine.

"Move on" means remove the erronous data from anything competitive.

It is clear to me examples such as what you have posted would be picked up very easily without accuracy data. I see little point in pointing them out. There is evidence here of approved devices providing similar erronous data that would just as easily have been identified without accuracy data. Clearly it is the less obvious errors that are the problem.

I can't really see anyone believe they broke the windsurfing speed record. But posting on a website does not imply they believe that data. They probably did not know what the data would say until they posted and could not be bothered to remove it. This does not however happen on the GPSTC where the data would be questioned immediately.

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vosadrian said..
Will you did actually say "of course, from 'non GPSTC approved' GPS's". I took that to imply that this could only happen from a non-approved device. I assume you were fishing for a query like mine.

Of course. And because errors of such stupendous magnitude are extremely rare or non existent on approved SDOP devices. Sure, we see errors in approved GPS devices occasionally, but the really big clangers are almost always in these non approved positional trackpoint devices.

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vosadrian said..
"Move on" means remove the erronous data from anything competitive.

Oh yes, great. and how do we know that

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vosadrian said..
It is clear to me examples such as what you have posted would be picked up very easily without accuracy data. I see little point in pointing them out. There is evidence here of approved devices providing similar erronous data that would just as easily have been identified without accuracy data. Clearly it is the less obvious errors that are the problem.

I'm very glad it's clear to you. This one should be pretty clear to everyone, but we could show you many examples where it is certainly NOT obvious without an SDOP device to compare it with. There are no examples from approved SDOP devices, that I know of, that have such a magniture of error. The largest number of errors we see from approved SDOP devices are user error. Examples like when someone leaves their GPS recording on the drive home etc. The other largest catagory of errors in approved SDOP devices is during crashes, and those are usually easily picked up by the filters using the verifying data available in those devices. The other less frequent source of bad data is when the GPS is worn in a compromised way. Slipping under the arm, inside a wetsuit or neoprene vest, in a backpack etc. These errors are also easy to verify with the full range of verifying data in these devices.

A lot of the error in non approved devices are the result of them using Positional data, not true Doppler data, for speed. That makes them far more suseptible to errors, large and small, even sailing along in a pretty normal way.

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vosadrian said..
I can't really see anyone believe they broke the windsurfing speed record. But posting on a website does not imply they believe that data. They probably did not know what the data would say until they posted and could not be bothered to remove it. This does not however happen on the GPSTC where the data would be questioned immediately.

Of course it implies they believe they did it. LOL! Or at least think someone else might believe it. What else would they leave it there? Perhaps just to seriously embarrass themselves

And in the GPSTC, you are quite correct.

I think a major reason you see less errors in approved devices on some random site you pickup files on is simply because there are a lot more non-approved devices and the users of such devices are less concerned with looking for errors. Many of them may not even care about the speed accuracy and are just uploading to keep a track of time/distance as a fitness activity. You can't compare the GPSTC data to some random site without an accuracy push.

And I highly doubt the people thought they did that speed. Your confidence in your implication is baseless. On Strava there are lots of people posting bogus data. Often people don't even check their data... it is just an automated process to upload. Even if they realise their data took a KOM from someone, it takes effort to remove it, and many can't be bothered. It does not mean they think they deserve the KOM.

I think all your post here does is show that GPS devices can have gross errors. You can choose to ignore them. But if you do in a forum that the data matters, others will realise that anyway. Gross errors are easily detected without any accuracy data.

Of course none of this has any bearing on the proposed GPSTC changes which do not ask for non-approved devices to be able to compete in competitive aspects of the GPSTC. With this change, the risk of non-approved devices effecting competitive results is removed. I don't believe anybody championing non-approved GPSTC devices is asking for them to be included in competitive aspects of the GPSTC. WE are just saying that we are happy with the quality of the data for our purposes and would like to continue to experience the social aspects of the GPSTC while using it is a tool to track our personal progress.

Hey guys most of us posting on gpstc understand all the issues with non-approved devices, it's been very well documented over the last couple of years. Adrian not sure why you continue to battle away on here, gpstc is run by volunteers who give their time, we don't really need any more arguing and debating clever points. It's been said already the person who set up Gpstc website doesn't have time to make changes to it. There is no one putting their hand up to collect subscriptions and organise a software developer to do it.

If you want to post your speed sailing results with an unofficial device you can do that on gps-speedsurfing, the site used by the European speedsailers. Why don't you sign up for that? You have to pay a small subscription to do so. It's worth noting though all of the competitions they run via that site all need to be posted with the same approved devices as gpstc, but you can still post for social interest with garmins etc.

Time to just leave it and have fun windsurfing rather than post stuff on seabreeze.