Select to expand quoteAusMoz said..sailquik said..AusMoz said..
I pressed some buttons accidently and the Garmin stopped, i started it again somehow. But to put it straight im trying to learn how to use it still, give me 1 to 2 years. I used the motion logger to post to Gpstc.
I had a look at that motion track and it is not what I expected to see. The satellite count is never as high as I am normally seeing, and it drops to 4 a large number of times. The only similar results I have seen were when i had the Logger on my pocket and it had a compromised sky view. Can you tell us how/where you were wearing the logger Moz?
Front of my NP buoyancy vest in plastic container
I'm sorry to say I think that is most likely the problem. I noticed that the satellite numbers change abripty as you turn around or change your position. That would be consistent with your body blocking a large proportion of the sky view and as you turn the unit will suddenly lose view of the satellites it is using and be forced to quickly acquire a different set. This aquisition can take a second ot two and during that time, the number of satellites being used can drop drastically. It is also likely that the material of the vest, if it is wet, is already weakening the signal at times, exacerbating things.
The Motion Logger has got a large and efficient antenna. That is unlikely to be the issue. Julien has tuned the device to only use satellite signals that are very strong. This is a deliberate strategy to increase accuracy. But this also relies on the user wearing the GPS where it has maximum 'sky view'. It is assumed that it will most likely be worn on the top of the Bicep. Even better is on the head, but this is not practical for many people. My limited testing so far shows a pretty small performance difference between in my helmet and on my bicep (facing up of course). But a very big difference if I put it in the front pocket of my jacket, and this is expecially apparent when I make a turn or change of direction. .
Stuff ups on my behalf on positions, touching things i shouldn't etc. I post to GPSTC with logger only, KA72 with Garmin and logger.
Maybe doing myself out of a few PB's maybe but I'm ok with that. I'm still learning the tech stuff with both.
You know, this forum is the only place I ever see people talking about how the human body blocks satellite signals. If that is true, it is bad news.
Granted, skiers, runners, bikers, and drivers have not demanded the extraordinary accuracy that we windsurfers/kiters need for official speed records, but they do not ever seem to be concerned about body interference or attenuation from vehicle structure or building structure.
Good heavens, we are already out on open water with about as good exposure to open sky as it is possible to get. Such as thing as having the logger/watch on the underside of a wrist should not be an issue. If it is, we need better receivers.
It's a trade-off, as usual. LCD Motion does not care, your watch does not care, Small Motion cares, surveying equipment cares. The latter two have better antennas when aimed correctly. Imagine the first two as light bulbs and the latter two as flashlights. The light bulb shines okayishly in all directions, the flashlight shines brighter in a single direction. If you have it strapped to your chest shining forward, your back is in the dark. Well, same thing in reverse : a "flashlight antenna" captures its cone much better but rejects the rest (which has its usefulness), a "light bulb antenna" captures all-around but not as well. The difference is much more visible on position than velocity.
Human body does effect signals, there's a whole field dedicated to minimizing this. Do you, for example, remember iPhone's catastrophe when hand placement killed signal?
www.engadget.com/2010-06-24-apple-responds-over-iphone-4-reception-issues-youre-holding-th.html
www.engadget.com/2010-06-24-some-iphone-4-models-see-signals-drop-to-0-when-held-left-handed.html
I'll bounce on your second thought and say regular people don't care for accuracy. To everyone around me excluding speedfreaks, GPS is somewhat right and it's good enough. It's free, it's cool, it helps. They don't mind being on the wrong side of the road or having distance increase while standing still. The value to them isn't in accuracy or truthfulness but having a rough idea and a convenient journal of their tracks.
I'll re-iterate another point before the police gets here : I really don't mind what anyone uses. Use what suits you.
I read your post again and I'd like to add that it's normal for you to not see this issue often simply because directional antennas take a lot of space (like 95% of Small Motion area, 20% of volume) and weight a brick so they aren't convenient for handhelds and thus, rare.
Select to expand quotesegler said..
You know, this forum is the only place I ever see people talking about how the human body blocks satellite signals. If that is true, it is bad news.
Granted, skiers, runners, bikers, and drivers have not demanded the extraordinary accuracy that we windsurfers/kiters need for official speed records, but they do not ever seem to be concerned about body interference or attenuation from vehicle structure or building structure.
Good heavens, we are already out on open water with about as good exposure to open sky as it is possible to get. Such as thing as having the logger/watch on the underside of a wrist should not be an issue. If it is, we need better receivers.
All these sports are point to point or laps, so you cross a line to start and finish.
Official Windsurfing speed records are still done the same way.
GPS opened up speed sailing to the masses, allowed us to sail whenever, wherever we liked. hence the need for document-able accuracy
Select to expand quotesegler said..
>> Such as thing as having the logger/watch on the underside of a wrist should not be an issue. If it is, we need better receivers.
If you look at the SDoP data from a GW60 worn on the wrist by a sailor using an underhand grip, you can see the difference between tracks.
No matter how good the receiver, if it's pointing at the water, there's going to be reflections. If the sky view changes mid gybe, it has to adjust to different sats. All this can lead to errors. I wondered why Manfred had set the SDoP filter to 6kts, when I don't normally see anything over 0.6kts. Apparently it's because the GW60 can drop that low mid gybe, I think because of the change from overhand to underhand.
Select to expand quotesegler said..
You know, this forum is the only place I ever see people talking about how the human body blocks satellite signals. If that is true, it is bad news.
It is very true, and it is bad news for many uses in many areas.
Select to expand quoteGranted, skiers, runners, bikers, and drivers have not demanded the extraordinary accuracy that we windsurfers/kiters need for official speed records, but they do not ever seem to be concerned about body interference or attenuation from vehicle structure or building structure.
Quite right. Those uses do not have need for more than the approximate positional accuracy of normal consumer grade GPS devices. Knowing where you are within 5 to 10 meters is perfectly acceptable in a huge number of uses. And as you also correctly point out, Windsurfers and kitesurfers who are interested in their speed for records and any type of ranking or competition, do need that higher accuracy to correctly order results where places are usually seperated by small differences in speed..Select to expand quoteGood heavens, we are already out on open water with about as good exposure to open sky as it is possible to get. Such as thing as having the logger/watch on the underside of a wrist should not be an issue. If it is, we need better receivers.
"..should not be an issue".???? Why not??? Becuse the physics are inconvenient for you? Water is a very effective radio signal blocker. (The human body is roughly 90% water) That is why submarines cant use radios and why sonar was invented. There is no magic receiver technology that can somehow 'suck' a direct radio signal around or through a blocking obstruction. If you happen to invent one, you will be rich and famous.
There is an enormous number of published articles on this in GPS related journals and such. Look up 'Muti-path' and 'urban canyons' for a start. Billions of Dollars have been spent launching extra specialised satellites into orbit to try to overcome the issues of navigation in 'urban canyons' in the large cities of the world. (eg. QZSS) Thankfully, Multi GNSS has helped massively with this issue by adding a large number of satellites so that more can be in view when sky view is limited, but you can't put satellites in the earth under you. The effects on accuracy of the underhand grip with the GW-60 is starkly illustrated by thousands of windsurfing session tracks. (it too has a directional antenna). There is no such thing as the universally perfect 'Unicorn' GNSS device. Nothing is everything to all users. Devices are optimised for specific uses. Tradeoffs are inherent in this. You choose your device according to your particular use needs.
Select to expand quotetbwonder said..
The next logical step is to try and code the alpha 500. This is far more difficult as all the other categories can be derived from distance travelled and speed. In order to calculate the alpha the position of each point needs to be recorded and the distance between the current point and all the recent points needs to be calculated every second.
The first problem is to try and define what an alpha actually is? We all know what it is but defining it exactly in code raises a few questions. How long is an alpha 500? I think KA72 defines it has a gybe with a length of 100 to 500 metres, in reality all the best gybes are very close to 500m. But I thought I should try and measure them all although this does mean more processing.
Then I thought it would be nice to also measure all those gybes that do not quite get back to inside the 50m circle. So I am thinking of something like this:
A page with two columns for Best of session and last alpha, then three rows showing the best 50 metre alpha, the best 60m alpha and the best 70 metre alpha. The 60 and 70 could be user configurable. As the example shows the higher radius alpha will produce faster speeds.
So when practicing alphas the user would be able see if those alphas that just missed out on the 50m radius, which I think would be interesting.
In testing I am comparing the results to the gybes measured on the "Motion". I think the "Motion" may only be recording 500m alphas. Does anybody know for sure?
Andrew,
Great to change the data fields for alpha for on water feedback. Have used a few times at 40-45-50 meters however going to try 45-50-55 next time. It is great how you can adjust the settings from Garmin connect on your phone for a particular session depending on location conditions for data fields to go Red when that number is achieved.
If people are interested to change settings below is the path on Garmin connect App on phone
Click Garmin connect /on watch device top of screen / activities & app Management / data Fields for GPSTC1 or 2 / settings brings up page to change and save via Bluetooth to your phone.
GPSTC field 1 with Alpha 500.
GPSTC field 2
Select to expand quotesailquik said..vosadrian said..
So was your claimed "scientific fact" actually a scientific fact?
I drive up the road 1000 times without having a crash. Is it a scientific fact I will not crash when I drive up the road?
Are you a 'Flat Eather' and 'antivaxer' too? 
No and no?
See I answered your questions rather than divert away from them when it does not suit you to give the answer.
There is no scientific fact showing that Garmins are inaccurate or less accurate than something else. You just like to exagerate to suit your purpose.
I can accept there is evidence that a garmin sometimes reads differently to another device you prefer (but cannot prove which is correct). But please refrain from using the term scientific fact or other terms like it when you don't understand the meaning. My term "perceived idea" was accurate.
Select to expand quotetbwonder said..
Since I have been spending more time inside than normal I have started work on writing a Datafield for my Garmin Fenix 3 to display the categories that we post to GPSTC. I feel this would be a useful addition to those of us who have an approved GPS on the shoulder and a Garmin on the wrist. It would be a nice match for the new "No display" Motion Simple Logger
I know there are some datafields already available, I have been using several for years, the biggest problem I find with them is that the fonts are too small to read without glasses. I aim to maximize the font size wherever possible. Ideally I would like to display all 6 categories in real time, but I have my doubts that I have the processing power to do the alpha 500.
Now I am not a computer programmer. The whole process has been a real battle. Progress has been slow and frustrating, but I am starting to get some results.
I am working on the two screens in the picture. They are fairly self explanatory, the coloured bars show how close your best 5 ten second runs are. At the top of the second screen the approx GPS signal quality is displayed and at the bottom the time of the session.
I have run into many problems, one unresolved issue is the different screens and fonts all the different Garmin watches support. The more detail I put on a screen the more incompatible the graphics appear on different watches.
So this is a call out to those who may be interested. What models of Garmin watch should I support? So far I am working on Fenix 3 and Fenix 5.
For those who are not aware Garmin Datafields can be downloaded for free from the Garmin IQ store and installed on most Garmin wathces. Don't look for this yet though as it is not yet published.
I feel I have to add that this is an on the water tool only, the results are not approved for posting to GPSTC. If you want to argue about that then please do it somewhere else.
Getting back to where this thread all started. "Garmin GPSTC Datafield - to complement the Motion Simple Logger"....
My Garmin is my "everyday" watch and Andrew's datafields have made it the perfect companion for my new motion logger, providing excellent feedback while sailing at the push of a button!!
Thanks again Andrew for all the skill, time and effort that went into developing them!!
Select to expand quotevosadrian said..
No and no?
See I answered your questions rather than divert away from them when it does not suit you to give the answer.
There is no scientific fact showing that Garmins are inaccurate or less accurate than something else. You just like to exagerate to suit your purpose.
I can accept there is evidence that a garmin sometimes reads differently to another device you prefer (but cannot prove which is correct). But please refrain from using the term scientific fact or other terms like it when you don't understand the meaning. My term "perceived idea" was accurate.
Nope. Wrong. You are in denial and have your head in the sand. Look around and read. There is evidence everywhere.
Do your own homework.
It would not matter what evidence was presented to you by me. You would not accept it.
There is none so blind as as those that will not see.
In any case, what Julien is doing is a HUGE SERVICE to the sport. What GPSTC is doing is a HUGE SERVICE to the sport.
We all applaud their work, even those of us who use GPS casually and archive their sessions on something like Strava.
Select to expand quotesailquik said..vosadrian said..
No and no?
See I answered your questions rather than divert away from them when it does not suit you to give the answer.
There is no scientific fact showing that Garmins are inaccurate or less accurate than something else. You just like to exagerate to suit your purpose.
I can accept there is evidence that a garmin sometimes reads differently to another device you prefer (but cannot prove which is correct). But please refrain from using the term scientific fact or other terms like it when you don't understand the meaning. My term "perceived idea" was accurate.
Nope. Wrong. You are in denial and have your head in the sand. Look around and read. There is evidence everywhere.
Do your own homework.
It would not matter what evidence was presented to you by me. You would not accept it.
There is none so blind as as those that will not see.
Evidence... yep. Scientific fact.... nope.
Select to expand quotevosadrian said.. >>Evidence... yep. Scientific fact.... nope.
So I ask again, define scientific fact.
Seems this argument is merely semantics
Select to expand quotevosadrian said..sailquik said..vosadrian said..
So was your claimed "scientific fact" actually a scientific fact?
I drive up the road 1000 times without having a crash. Is it a scientific fact I will not crash when I drive up the road?
Are you a 'Flat Eather' and 'antivaxer' too?
No and no?
See I answered your questions rather than divert away from them when it does not suit you to give the answer.
There is no scientific fact showing that Garmins are inaccurate or less accurate than something else. You just like to exagerate to suit your purpose.
I can accept there is evidence that a garmin sometimes reads differently to another device you prefer (but cannot prove which is correct). But please refrain from using the term scientific fact or other terms like it when you don't understand the meaning. My term "perceived idea" was accurate.
I believe they like to use a feelings based system with no limits or specific criteria. The most ironic thing is that people who don't understand gps or basic programming functions of the gps chip enough to make one ( a simple task) have a secret recipe to judge the performance of one made by someone with that knowledge.....
Select to expand quotedecrepit said..vosadrian said.. >>Evidence... yep. Scientific fact.... nope.
So I ask again, define scientific fact.
Seems this argument is merely semantics
I'm not the one who introduced the term to this thread. A definition was provided by Sailquik (which he must have had to google) which debunked his own use of the term.
Yep, it is about semantics. Don't go using big words you don't understand (amounting to making a false claim) in a failed attempt to prove a point.
There is very little in the way of scientific facts in relation to GPS accuracy. It is so complex with so many variables. I mean can you even prove the satelites which provide the signals are where/when/velocity they claim to be (which is the basis of all the calculations)? The best you can do is look at data and repeatability of results and use statistical analysis to form a conclusion. I could make a device with an accelerometer that whenever it detects movement reports a speed of 30.00 knots. It would be repeatable to better than 0.0000001% (add as many decimal points as you like!!).
I'm not saying that there is not evidence that one GPS is more accurate than another. I am just saying that you can make lots of claims of Garmin products inaccuracy, but you are just comparing them to something you have decided is better and then discounting something that reads differently. Many are perfectly happy with the data of these lesser devices. I believe there was a poll done some time ago which showed this.
If you read this crap and thought he might have made a good argument, private message me and I'll reply. I'm not feeding the troll.
Only PM I received :
"Best not to comment on Seabreeze Julien or people may stop buying your device."
Select to expand quoteJulienLe said..
Only PM I received :
"Best not to comment on Seabreeze Julien or people may stop buying your device."
This must be a joke and actual pathetic ....
FFS... Andrew with his Garmin app and Julien with the Motion gives more of us a chance to share the stoke... probably better for the naysayers to take it offline
Julien... your device is soooo good and sooo simple to use and I am sure it will help our Team Challenge to develop. My quote to you..."The lion doesn't worry about the opinion of sheep."
KEEP AT IT.
Is there any posts in this thread or elsewhere on seabreeze where anyone says anything negative about Julien's devices?
I have nothing against them. I'm glad they work for those who get them. I just don't personally want one myself.
Select to expand quotevosadrian said..
Is there any posts in this thread or elsewhere on seabreeze where anyone says anything negative about Julien's devices?
The only problems with Julien's devices is mainly out of his control. That's why the big delays. But Julien may be described as a perfectionist and won't let anything he thinks 2nd rate past him.
There's one example of something less than ideal, the original holder of the first motions lost their grip in a major stack and a couple have been lost. This was unexpected, the force of a big crash on stuff can do unexpected things. But Julien quickly responded with a good fix. So there's not 100% perfection, but the desire and drive is there for it. That's about the best we can hope for in any human undertaking.
I think you miss my point. Julien is getting defensive and others are getting defensive on his behalf with talk of naysayers etc. I can't see why. I don't believe anyone in this thread or elsewhere on seabreeze has said anything negative of his products.
Select to expand quotevosadrian said..
I think you miss my point. Julien is getting defensive and others are getting defensive on his behalf with talk of naysayers etc. I can't see why. I don't believe anyone in this thread or elsewhere on seabreeze has said anything negative of his products.
Hmm, yes I certainly don't read it that way, Julien is just answering questions, being his normal honest open self. I don't see anything defensive about it.
Select to expand quotevosadrian said..
I think you miss my point. Julien is getting defensive and others are getting defensive on his behalf with talk of naysayers etc. I can't see why. I don't believe anyone in this thread or elsewhere on seabreeze has said anything negative of his products.
Adrian, you have missed the point I think. This thread is about Garmin app and Motiion logger. Not the hows what's and why's of the GPSTC.
So therefore the debates on accuracy should be elsewhere...Happy Sailing
Adrian, I'm with Mr Keen give up your just causing grief and stress to Admin who do a thankless job you should do as others stick to the rules and except them or leave. Nothing needs to change nothing needs fixing with TC people are sick of the whingers trying to make themselves feel important.
Rebel have the Garmin 935 at 50% off at the moment: $374
www.rebelsport.com.au/p/garmin-forerunner-935-gps-heart-rate-watch-black-532877.html
Hey Andrew - just wanted to thankyou for your app.
Because I'm a dumbarse it has taken me a while to work out how to do datafields but now I have it it is bloddy terrific!
It compliments Juliens simple motion perfectly.
Julien - thanyou for the motion - it is also bloddy terrific!!
I was surprised how easy it was to use - even for a dumbarse!
cheers
