Forums > Windsurfing   Gps and Speed talk

GPS Watches

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Created by segler Tuesday, 15 Apr 2019
segler
73 posts
Tuesday , 15 Apr 2019 11:37PM
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The GW-60 is a great GPS watch for our sport.

If you want, however, a GPS watch but don't need to have it as an official speed logger, there are lots of other choices out there.

All I want is actual on-water speed, distance, and max speed. I don't need heart rate or any other fitness stuff. I don't need bluetooth or wifi. I am perfectly happy with cable data and charging. The GW-60 is great for this.

However, you can get this same GPS functionality from many other watches, including Garmin watches.

My alternative to the GW-60 is the Timex Ironman GPS. No fitness stuff, just basic GPS information, and simple micro-usb cable upload and charging. No bluetooth or wifi to complicate the firmware. PC upload through industry-standard micro-usb cable to a PC Timex utility that can interface with Strava or Endomondo or some others.

The point is this: simple watch, simple cabling (industry-standard micro-usb instead of proprietary clamps), simple firmware, simple storage and display. The Timex is on Amazon for $74 US. One third the cost of the GW-60 and most of the Garmins.

I have worn both the GW-60 and the Timex on the same arm for several sessions to compare results. On-water speed, distance, and max speed all come in within 1-2% of each other, consistently. Battery life for the two is about the same, both for watch mode and for GPS.

Te Hau
353 posts
Tuesday , 16 Apr 2019 6:50AM
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Waterproof?

getsum
NSW, 23 posts
Tuesday , 16 Apr 2019 10:29AM
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segler said..
The GW-60 is a great GPS watch for our sport.

If you want, however, a GPS watch but don't need to have it as an official speed logger, there are lots of other choices out there.

All I want is actual on-water speed, distance, and max speed. I don't need heart rate or any other fitness stuff. I don't need bluetooth or wifi. I am perfectly happy with cable data and charging. The GW-60 is great for this.

However, you can get this same GPS functionality from many other watches, including Garmin watches.

My alternative to the GW-60 is the Timex Ironman GPS. No fitness stuff, just basic GPS information, and simple micro-usb cable upload and charging. No bluetooth or wifi to complicate the firmware. PC upload through industry-standard micro-usb cable to a PC Timex utility that can interface with Strava or Endomondo or some others.

The point is this: simple watch, simple cabling (industry-standard micro-usb instead of proprietary clamps), simple firmware, simple storage and display. The Timex is on Amazon for $74 US. One third the cost of the GW-60 and most of the Garmins.

I have worn both the GW-60 and the Timex on the same arm for several sessions to compare results. On-water speed, distance, and max speed all come in within 1-2% of each other, consistently. Battery life for the two is about the same, both for watch mode and for GPS.




Thanks.
I've been looking for something basic and easy to use.

John340
QLD, 1920 posts
Tuesday , 16 Apr 2019 11:27AM
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Oh the can of worms has been opened again

decrepit
WA, 9033 posts
Tuesday , 16 Apr 2019 12:50PM
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John340 said..
Oh the can of worms has been opened again


Segler did say, "If you don't need to have it for an official speed logger". In other words, not acceptable for posting to the GTC.

sailquik
VIC, 4462 posts
Tuesday , 16 Apr 2019 4:00PM
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Trackpoint 'positional speed to Doppler? The difference can easily be 2%. Doppler derived speed can be far more consistently accurate.
But yes, for what you want, any old GPS can suffice. Accuracy and verifiability is not really vital.

jirvin4505
QLD, 997 posts
Tuesday , 16 Apr 2019 6:19PM
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Similar needs myself after giving up on the 3 gw60s I've spent nearly $1000 on

i followed suggestions on this forum for an affordable on water option. I'm using the suunto watch $150aud

(Waiting for the motion to mature before I lash out again)

really like the Bluetooth download to my phone = I can have tracks downloaded and discussed while derrigging

its no gw60 in terms of accuracy A good catapult has me recording peak pb's

However as a day to day on water monitor it's great. I'm saving the gw31 for special days

cheers jeff

Rob11
195 posts
Tuesday , 16 Apr 2019 4:42PM
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decrepit said..

John340 said..
Oh the can of worms has been opened again



Segler did say, "If you don't need to have it for an official speed logger". In other words, not acceptable for posting to the GTC.


Pretty sure there was no mention of GTC in the initial post... hmm who's opening the can!!

decrepit
WA, 9033 posts
Tuesday , 16 Apr 2019 4:57PM
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Rob11 said.. Pretty sure there was no mention of GTC in the initial post... hmm who's opening the can!!


Nobody! ---- Was my point.

boardsurfr
WA, 752 posts
Tuesday , 16 Apr 2019 5:38PM
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jirvin4505 said..
its no gw60 in terms of accuracy A good catapult has me recording peak pb's

However as a day to day on water monitor it's great. I'm saving the gw31 for special days

cheers jeff


That's pretty much the issue. In most of the sessions, the results will be very close. But every now and then, you'll get a big error, often (but not always!) from a catapult. I can happen with the "approved" GPS devices, too - my wife had a 40-knot catapult with a GT-31 the first time she sailed a speedboard. But with GW-60 (etc.) data, artifacts usually have high error estimates, and can easily be identified.

The issue is not just big catapults that result in numbers that are obviously wrong. Perhaps the bigger problems are smaller errors where the speed is "inflated" just a few knots.

But for everyday sailing outside of competitions, any GPS watch will usually do a decent job. The Timex looks like a good find. Just be a bit skeptical if it tells you that you've gone faster than ever before .

segler
73 posts
Tuesday , 16 Apr 2019 10:39PM
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Yes, the Timex is waterproof. It even has a built-in workout for swimming, along with biking, running, and other. These workouts are all changeable. I tweaked "other" for windsurfing: on-water speed, distance, and maximum speed.

Doppler. Pretty much all gps units these days measure speed with doppler since picosecond timing is very easy to do with 50-cent circuits these days. I know that Garmin hand-held hiking gps units in 1985 used doppler for speed. All automotive units use doppler for speed. Civilian gps can measure our positions to within 30 feet (sometimes 10 feet), not so great, but they can measure our speeds to within 0.01 cm/sec due to the accuracy of timing.

The really great thing about the GW-60 is the 2-second and 10-second point smoothing. My old Garmin Legend does not have this, as evidenced by the occasional single super high speed point that gets captured in the max speed. I don't know whether the Timex has smoothing. I do know that the Timex and the GW-60 give virtually identical results for the several sessions I have tested them together on the same arm.

If I ever need bluetooth or heart rate, I have a Amaxfit BIP. However, it is more complicated to use. The GW-60 and Timex are dead simple to use.

decrepit
WA, 9033 posts
Wednesday , 17 Apr 2019 8:28AM
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segler said. >


Smoothing? My understanding is it's just the average of the 5hz data.

sailquik
VIC, 4462 posts
Wednesday , 17 Apr 2019 2:19PM
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segler said..
Doppler. Pretty much all gps units these days measure speed with doppler since picosecond timing is very easy to do with 50-cent circuits these days. I know that Garmin hand-held hiking gps units in 1985 used doppler for speed. All automotive units use doppler for speed. Civilian gps can measure our positions to within 30 feet (sometimes 10 feet), not so great, but they can measure our speeds to within 0.01 cm/sec due to the accuracy of timing.

The really great thing about the GW-60 is the 2-second and 10-second point smoothing. My old Garmin Legend does not have this, as evidenced by the occasional single super high speed point that gets captured in the max speed. I don't know whether the Timex has smoothing. I do know that the Timex and the GW-60 give virtually identical results for the several sessions I have tested them together on the same arm.

If I ever need bluetooth or heart rate, I have a Amaxfit BIP. However, it is more complicated to use. The GW-60 and Timex are dead simple to use.



Wrong!

Many old GPS's, including the Garmin Foretrex 201, Geko and Legend etc, did seem to use Doppler speed for their Display, but could not record the Doppler speeds. All they record is positional data.

The first GPS we had that could RECORD the Dopper speeds was the GT-11, and initially that was just in NMEA data.
Many cuurent model sports watches STILL dont record the Doppler Speed Data. For example, the Suunto watch appears to record Doppler speed, but it actually just smoothed positional speed, and is therefore both optimistic and subject to random large errors.
Again, they probably do display the Doppler speed on the screen. That is very different from actually recording it.

The GW-60 does not use 'smoothing'. It's data is filter free. If you record at 1Hz, the recorded data is the average of the 5 points for that second. OK, that is a kind of a 'smoothing', If you record the raw 5Hz data, it is not filtered/smoothed.

The numbers given by the GPS vendors, like the example is just best case scenario. All datasheet statistics come from a laboratory controlled environment, using a GNSS simulator, with strong pure signals, collecting data over a 24-hour run from which statistics are calculated. They are very optimistic compared with the real workd experience. There is certainly no guarantee you will actually get that even most of the time. That is why the 'error estimate' data that we get from some GNSS chips is so important. And it shows clearly that the individual point error is quite a bit higher than the claimed best case specifications.

And I think you mean 0.01M/sec. Even lab test accuracy of 0.01mm/sec would be astonishing!

The Garmin Legend anomoly results you see are what we used to call 'Spikes' and are associated with positional data. Thankfully, we don't seem much of that level of error anymore with Doppler speed data.

And is your Timex/GW-60 comparision data always 'virtually identical???' And what is 'virtually?

yoyo
WA, 1603 posts
Wednesday , 17 Apr 2019 12:41PM
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jirvin4505 said..
I really like the Bluetooth download to my phone = I can have tracks downloaded and discussed while derigging




You could just use a Zume5 with gpsLogit. $14.50. Appears very sensitive and accurate doppler recording and no spikes in catapults.

getsum
NSW, 23 posts
Wednesday , 17 Apr 2019 3:54PM
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yoyo said..

jirvin4505 said..
I really like the Bluetooth download to my phone = I can have tracks downloaded and discussed while derigging





You could just use a Zume5 with gpsLogit. $14.50. Appears very sensitive and accurate doppler recording and no spikes in catapults.



What's the best way to setup the android handset? buy a SIM card starter pack , or on a plan? get a phone number etc , with data option?

sailquik
VIC, 4462 posts
Wednesday , 17 Apr 2019 4:06PM
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It depends on what you want to do. If you just want the phone to run GPS-Logit, just get a cheap starter kit like the Zume5 Boost one. No need to even insert the sim card to use it.

If you want to connect to the Mobile network, there are plently of Starter Kit deals around, including from Boost and Testra, (so they work with the Boost kit) for '$30' and '$40' prepaid for $10-$20.

I like the way GPS-Logit talks to me and tells me my speed every second. I especially like the way it announces my 'Last Run' as soon as I drop below the theshold speed (I set it to 20 Knots).

getsum
NSW, 23 posts
Wednesday , 17 Apr 2019 4:34PM
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sailquik said..
It depends on what you want to do. If you just want the phone to run GPS-Logit, just get a cheap starter kit like the Zume5 Boost one. No need to even insert the sim card to use it.

If you want to connect to the Mobile network, there are plently of Starter Kit deals around, including from Boost and Testra, (so they work with the Boost kit) for '$30' and '$40' prepaid for $10-$20.

I like the way GPS-Logit talks to me and tells me my speed every second. I especially like the way it announces my 'Last Run' as soon as I drop below the theshold speed (I set it to 20 Knots).


Thanks for the info, sounds like a good option I guess just put it in a sealed bag.

so no need for a SIM card? I don't understand how it works without one?

yoyo
WA, 1603 posts
Wednesday , 17 Apr 2019 3:03PM
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All phones connect to the cell network even without a sim. (unless you kill the radio transmitter by putting it in flight mode) This is why you can make emergency calls even without a sim.
The sim just identifies you so they know who to bill etc and if you are paid up (prepaid) and to connect to another user.
Most phones gps' still work in "flight mode" as the gps is a passive receiver. This is the case with the Zume. I turn the radio transmitter off ( flight mode) to increase battery life. (This also kills bt and wifi) gpsLogit works fine like this.
So as Andrew says. No need to even insert the sim. For 15 bucks you get a very accurate 1hz gps recorder that talks to you and has a 4" display. Plus you can make emergency calls with it over the telstra network if you get in trouble.

getsum
NSW, 23 posts
Wednesday , 17 Apr 2019 5:12PM
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yoyo said..
All phones connect to the cell network even without a sim. (unless you kill the radio transmitter by putting it in flight mode) This is why you can make emergency calls even without a sim.
The sim just identifies you so they know who to bill etc and if you are paid up (prepaid) and to connect to another user.
Most phones gps' still work in "flight mode" as the gps is a passive receiver. This is the case with the Zume. I turn the radio transmitter off ( flight mode) to increase battery life. (This also kills bt and wifi) gpsLogit works fine like this.


Oh right very interesting !

Thanks for that info.

getsum
NSW, 23 posts
Wednesday , 17 Apr 2019 5:14PM
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yoyo said..
All phones connect to the cell network even without a sim. (unless you kill the radio transmitter by putting it in flight mode) This is why you can make emergency calls even without a sim.
The sim just identifies you so they know who to bill etc and if you are paid up (prepaid) and to connect to another user.
Most phones gps' still work in "flight mode" as the gps is a passive receiver. This is the case with the Zume. I turn the radio transmitter off ( flight mode) to increase battery life. (This also kills bt and wifi) gpsLogit works fine like this.
So as Andrew says. No need to even insert the sim. For 15 bucks you get a very accurate 1hz gps recorder that talks to you and has a 4" display. Plus you can make emergency calls with it over the telstra network if you get in trouble.


Is gps logit an Android only app?

decrepit
WA, 9033 posts
Wednesday , 17 Apr 2019 3:52PM
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Yep.

getsum
NSW, 23 posts
Wednesday , 17 Apr 2019 6:05PM
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decrepit said..
Yep.


cool thanks

remery
WA, 358 posts
Wednesday , 17 Apr 2019 7:37PM
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You will be assimilated.

segler
73 posts
Wednesday , 17 Apr 2019 10:50PM
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Averaging 5 Hz data is a way of smoothing. Not as smart as AI methods that will reject outliers, but good enough for our use. The other really nice thing about the GW-60 is SPD GENIE. With the right settings, it is very easy to use. Fire it up with the gps button, and go sailing. Stop and read your results. No button presses necessary.

Light speed is 3e+10 cm/sec. If you multiply that by one picosecond 1e-12, you get 3e-2 cm, or 0.03 cm. Sorry, I was off by a factor of 3, but not a power of 2. Picosecond circuit timing has been around since the 60s.

Since positional accuracy for civilian gps is no better than 30 feet, sometimes 10 feet, using delta-position/delta-time is not a good way to calculate speed. To my knowledge, no modern gps units do it that way. They all use doppler. Even my ancient Garmin Legend from 1985 yses doppler.

However, almost none of them use smoothing (averaging) like the GW-60. As we all now know, without smoothing, speeds can be very noisy. When I first experimented with gps on a windsurfer, I mounted my trusty old Garmin Legend on the front of the boom in a aquapac bag. Very noisy, and I usually got max speed numbers like 130 mph. When I then mounted it to my upper arm, everything got quiet, and my max speed was realistic (say, 25-30 mph), consistently.

I don't know whether the Timex Ironman GPS uses smoothing. However, it gives speed results within 1-2% of the GW-60. When I plot Timex speeds in Timex Connect or Endomondo or Strava, the plots are smooth. No spikes. Since it is meant to be worn on the wrist while running (with the wrist swinging back and forth), it would not surprise me if it has some kind of smoothing (or averaging) of speed data.

I never see speed spikes in the Garmin Nuvi automotive units, either, and max speeds never show weird spiky results.

Where the GW-60--and a couple others--beats everybody else is in the reporting/upload of error data. This is most excellent for official speed records.

JulienLe
43 posts
Thursday , 17 Apr 2019 11:22PM
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If anyone really wants to know how GNSS receivers work, how accuracy/precision/repeatability are impacted, why some receivers are more expensive than others, why surveyors use 30kUSD equipments, why larger devices are better than smaller ones, how outliers are excluded, how dynamic profiles work and so on, there are many free public videos and lectures about it. It's a massive, well-researched, very accessible field.

sailquik
VIC, 4462 posts
Thursday , 18 Apr 2019 10:53AM
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Segler, Did you not read my last post?

NO! The Garmon Legend DID NOT RECORD Doppler speeds. Show me your data with Doppler speeds in it and I will show you a Unicorn! This was why the GT-11 was such a breakthrough GPS for us.

And no, some current GPS watches STILL dont record the Doppler speeds, only position.

When we refer to 'smoothing' in GPS files, we usually are refering to a specific filter, like a low pass filter. Do you use your GW-60 on 1Hz?

And NO! The small occilateions you see on a speed graph are not all 'Noise'. They are just as likely to be actual real changes in speed measurement from real movement. Superimpose the speed graphs of two 5Hz gps worn side by side and see that those occilations actually match on a non random way to a large extent. There are other possible explanations for this, but one is that they are actually measuring real speed variations.

Yes, we determined many years ago that using positional trackpoint data for speed measurement was prone to large inaccuracies. This is why all credible GPS windsurfing switched to using Doppler speed data.

The GW-60 does NOT use any 'smoothing' algorithms at 5Hz. There is no low pass filter as there appears to be in the GT-31. It is extremely likely that a GPS device designed to be used on the wrist while running DOES have some very effective smoothing filters applied to the output. Otherwise the speed data would look terrible. (instead of amore accurate, but all over the place )

I don't know why you are so focused on picosecond circuit timing. But yes, extremely accurate time keeping has been an essential feature of all GPS devices since day one. Otherwise thay would not work!

That does not mean that a GPS can give speed accuracy to 0.03cm/sec. Read the manufacturers specifications. None of them claim anywhere near that as far as I am aware. The best I have seen claimed is 0.05M/sec! (UbloxM8) Until recently, the best I saw claimed was 0.1M/sec. And as I pointed out, that is a lab test figure. Not one you would typically get in real life use.

I would love to see a saved doppler speed data track from a Garmin Nuvi automotive unit. Please PM me me and a send me one.

Boston!
NSW, 48 posts
Thursday , 18 Apr 2019 3:37PM
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sailquik said..
Segler, Did you not read my last post?

NO! The Garmon Legend DID NOT RECORD Doppler speeds. Show me your data with Doppler speeds in it and I will show you a Unicorn! This was why the GT-11 was such a breakthrough GPS for us.

And no, some current GPS watches STILL dont record the Doppler speeds, only position.

When we refer to 'smoothing' in GPS files, we usually are refering to a specific filter, like a low pass filter. Do you use your GW-60 on 1Hz?

And NO! The small occilateions you see on a speed graph are not all 'Noise'. They are just as likely to be actual real changes in speed measurement from real movement. Superimpose the speed graphs of two 5Hz gps worn side by side and see that those occilations actually match on a non random way to a large extent. There are other possible explanations for this, but one is that they are actually measuring real speed variations.

Yes, we determined many years ago that using positional trackpoint data for speed measurement was prone to large inaccuracies. This is why all credible GPS windsurfing switched to using Doppler speed data.

The GW-60 does NOT use any 'smoothing' algorithms at 5Hz. There is no low pass filter as there appears to be in the GT-31. It is extremely likely that a GPS device designed to be used on the wrist while running DOES have some very effective smoothing filters applied to the output. Otherwise the speed data would look terrible. (instead of amore accurate, but all over the place )

I don't know why you are so focused on picosecond circuit timing. But yes, extremely accurate time keeping has been an essential feature of all GPS devices since day one. Otherwise thay would not work!

That does not mean that a GPS can give speed accuracy to 0.03cm/sec. Read the manufacturers specifications. None of them claim anywhere near that as far as I am aware. The best I have seen claimed is 0.05M/sec! (UbloxM8) Until recently, the best I saw claimed was 0.1M/sec. And as I pointed out, that is a lab test figure. Not one you would typically get in real life use.

I would love to see a saved doppler speed data track from a Garmin Nuvi automotive unit. Please PM me me and a send me one.


Oh, oh. You're in big trouble now, Segler.

seanhogan
3007 posts
Thursday , 18 Apr 2019 3:02PM
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Yes... when Daffy starts using CAPITALS you better hide...

sailquik
VIC, 4462 posts
Thursday , 18 Apr 2019 5:16PM
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seanhogan said..
Yes... when Daffy starts using CAPITALS you better hide...


HA-HA!

fangman
WA, 838 posts
Thursday , 18 Apr 2019 3:27PM
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Boston! said..


sailquik said..
Segler, Did you not read my last post?

NO! The Garmon Legend DID NOT RECORD Doppler speeds. Show me your data with Doppler speeds in it and I will show you a Unicorn! This was why the GT-11 was such a breakthrough GPS for us.

And no, some current GPS watches STILL dont record the Doppler speeds, only position.

When we refer to 'smoothing' in GPS files, we usually are refering to a specific filter, like a low pass filter. Do you use your GW-60 on 1Hz?

And NO! The small occilateions you see on a speed graph are not all 'Noise'. They are just as likely to be actual real changes in speed measurement from real movement. Superimpose the speed graphs of two 5Hz gps worn side by side and see that those occilations actually match on a non random way to a large extent. There are other possible explanations for this, but one is that they are actually measuring real speed variations.

Yes, we determined many years ago that using positional trackpoint data for speed measurement was prone to large inaccuracies. This is why all credible GPS windsurfing switched to using Doppler speed data.

The GW-60 does NOT use any 'smoothing' algorithms at 5Hz. There is no low pass filter as there appears to be in the GT-31. It is extremely likely that a GPS device designed to be used on the wrist while running DOES have some very effective smoothing filters applied to the output. Otherwise the speed data would look terrible. (instead of amore accurate, but all over the place )

I don't know why you are so focused on picosecond circuit timing. But yes, extremely accurate time keeping has been an essential feature of all GPS devices since day one. Otherwise thay would not work!

That does not mean that a GPS can give speed accuracy to 0.03cm/sec. Read the manufacturers specifications. None of them claim anywhere near that as far as I am aware. The best I have seen claimed is 0.05M/sec! (UbloxM8) Until recently, the best I saw claimed was 0.1M/sec. And as I pointed out, that is a lab test figure. Not one you would typically get in real life use.

I would love to see a saved doppler speed data track from a Garmin Nuvi automotive unit. Please PM me me and a send me one.




Oh, oh. You're in big trouble now, Segler.



Oh the humanity Segler ! What have you done...!!
If you mix elemental Daffy + a trace of Garmin GPS in any forum with GPS you get => ****ushima. Throw in a trace of Bold and we are all doomed....

fangman
WA, 838 posts
Thursday , 18 Apr 2019 3:31PM
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oops ^ The net nanny is censoring the japanese nuclear reactor starting with Fu



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Forums > Windsurfing   Gps and Speed talk


"GPS Watches" started by segler