Any setup without Glonass works fine. At least here in Europe where Beidou and QZSS can not be received (I guess).

- Multiband is theoretically great because you can differentiate between bands to remove some noise.
- Multiband is improbable in smartwatches because you need two receivers, two amplifiers, two filters, two antennas, two locks and there isn't energy/volume for it so one band has to be prioritized anyway.
- Multiband isn't that interesting to us because we don't have multipath or reception issues on water.

At the root of it all are engineering decisions. How much energy can you give it, how much volume can you give it, how much money can you spend on it. If you use low-energy tricks to boast about lifetime, you're sacrificing something else.

I feel like a disclaimer is missing from this topic? Xbraun54 sells Coros watches and ico has been promoting them on Facebook ever since.

hi, i used my new Fenix 7 saphir 3-4 time for speedsurfing here on the lake and felt that the fenix 7 shows too low speeds...

so i took the old fenix 5 plus and a GT31 with me.

On the Water the F5 plus and the GT31 showed always same Topspeed .. like +-0.5 km/h but the Fenix 7 always showed lower speeds liek -2kmh

The Fenix 7 i used in the multiband mode..

atteched you see the results.. but what did this tell us?

The Fenix 7 is ****?

Select to expand quote

tabou123 said..
hi, i used my new Fenix 7 saphir 3-4 time for speedsurfing here on the lake and felt that the fenix 7 shows too low speeds...

so i took the old fenix 5 plus and a GT31 with me.

On the Water the F5 plus and the GT31 showed always same Topspeed .. like +-0.5 km/h but the Fenix 7 always showed lower speeds liek -2kmh

Hi. I'm currently doing some analysis on this topic which I will ultimately share with everyone.

Would you be able to send me the track data for these devices via e-mail?

I'll drop you a PM with my e-mail address.

TIA, Mike

I'll post a couple of screenshots and my thoughts on the data of tabou123.

The GT-31 and Fenix 5 Plus results are very comparable with the two generally within 0.1-0.2 knots for results across the various speed categories. However, the Fenix 7 is reporting much lower than the other two devices.

The image below shows the Fenix 5 Plus (left) vs Fenix 7 (right). I've displayed the tracks such that the "Doppler speeds" (n.b. we don't know for sure what Garmin is recording) and non-Doppler speeds are overlaid. The speed data from the Fenix 5 looks typical of a working GPS device and the speed graphs closely match the GT-31, especially what I suspect to be the Doppler-derived speeds. n.b. I won't go into why I think the speeds from the Fenix 5 Plus are Doppler-derived right now, since it's a topic in its own right.

The Fenix 7 speed data (right image) looks very similar in nature to my friend's Fenix 7 track. What should be the Doppler-derived data is shifted right by several seconds, it is heavily smoothed and has flattened peaks.



Aside from the heavy smoothing (likely a basic rolling average but without centring, plus some basic filtering when stationary) there are also some weird downward spikes in the speed data. The shifting to the right wasn't present in tracks from an earlier version of the Fenix 7 firmware but the downward spikes were also present in tracks that I have seen from the earlier firmware.



Garmin are definitely doing something peculiar with the speed data received from the GNSS chip. So far as I know it's the same chip as the COROS VERTIX 2 and that watch doesn't have these issues.

I'd be sure to complain to Garmin if I owned a Fenix 7. They should definitely look to fix this issue!

Anyone contacted Garmin about this? I just bought a Forerunner 255 to replace my old 920XT. The 255 has the same multi-band chipset as the Fenix sapphire, but it's only $350, and I'm worried it has the same issues.

Well I had my tracks reviewed and it seems the same thing happens on the 255 which is extremely frustrating. In good/bad news it fell off my wrist gybing so I'll be buying a new watch soon. It won't be a garmin if this issue isn't addressed.
My 920xt from ~8 years ago is still my go-to. Unfortunately it sucks at everything else and I constantly hit the giant buttons while on the water by accident.

I reported this issue to garmin and I'll update this with any response from them.

Select to expand quote

JulienLe said..
- Multiband is theoretically great because you can differentiate between bands to remove some noise.
- Multiband is improbable in smartwatches because you need two receivers, two amplifiers, two filters, two antennas, two locks and there isn't energy/volume for it so one band has to be prioritized anyway.
- Multiband isn't that interesting to us because we don't have multipath or reception issues on water.

At the root of it all are engineering decisions. How much energy can you give it, how much volume can you give it, how much money can you spend on it. If you use low-energy tricks to boast about lifetime, you're sacrificing something else.

@Julien - As an electronics engineer myself, I understand where this sentiment comes from -> when we understand stuff, we are usually pretty accurate with future advancement, but we can also make quite inaccurate predictions. You posted this message in March 2022 -> as of June 2022 you could buy a Garmin 955 with multiband-GNSS -> it is quite position-accurate (I have not tested its Doppler accuracy).

Multiband is one of the best features that we can have in modern GPS's. We dont need multiple receivers -> back in the 90's all GPS's had multiple receivers, with one for each satellite. There were some gps's with up to 12 receivers, but they were expensive and bulky. Then we figured out frequency-multiplexing using digital-demultiplexing, thus we only needed single receiver. Same applies to multiband situation, we have now figured out how to use a single receiver.

20 yrs ago GPS antenna's needed to be at least 70x70mm, then we went to 20x20mm. 10'ish years ago GPS chip-antennas' largely didn't exist, now they dominate.

We have miniaturised the signal-reception, demultiplexing, co-ordinate computation, and so on -> we now have space to add touchscreens and solar-panels to watches. My point is, nothing stands still -> technology is advancing as time marches on.

PS. we definitely have multipath reception issues on water - we have direct-line-of-sight to the satellite and a single-reflection to the same satellite.

Select to expand quote

tabou123 said..
hi, i used my new Fenix 7 saphir 3-4 time for speedsurfing here on the lake and felt that the fenix 7 shows too low speeds...

so i took the old fenix 5 plus and a GT31 with me.

On the Water the F5 plus and the GT31 showed always same Topspeed .. like +-0.5 km/h but the Fenix 7 always showed lower speeds liek -2kmh

The Fenix 7 i used in the multiband mode..

atteched you see the results.. but what did this tell us?

The Fenix 7 is ****?

Are you using 1s recording or smart recording? My experience with smart recording, is that it is less accurate.

Select to expand quote

tabou123 said..
hi, i used my new Fenix 7 saphir 3-4 time for speedsurfing here on the lake and felt that the fenix 7 shows too low speeds...

so i took the old fenix 5 plus and a GT31 with me.

On the Water the F5 plus and the GT31 showed always same Topspeed .. like +-0.5 km/h but the Fenix 7 always showed lower speeds liek -2kmh

The Fenix 7 i used in the multiband mode..

atteched you see the results.. but what did this tell us?

The Fenix 7 is ****?

Strange. I'll compare my Fenix 7 solar with GW-60 tomorrow to check this

Select to expand quote

Hogar said..

tabou123 said..
hi, i used my new Fenix 7 saphir 3-4 time for speedsurfing here on the lake and felt that the fenix 7 shows too low speeds...

so i took the old fenix 5 plus and a GT31 with me.

On the Water the F5 plus and the GT31 showed always same Topspeed .. like +-0.5 km/h but the Fenix 7 always showed lower speeds liek -2kmh

The Fenix 7 i used in the multiband mode..

atteched you see the results.. but what did this tell us?

The Fenix 7 is ****?

Strange. I'll compare my Fenix 7 solar with GW-60 tomorrow to check this

Select to expand quote

Hogar said..

tabou123 said..
hi, i used my new Fenix 7 saphir 3-4 time for speedsurfing here on the lake and felt that the fenix 7 shows too low speeds...

so i took the old fenix 5 plus and a GT31 with me.

On the Water the F5 plus and the GT31 showed always same Topspeed .. like +-0.5 km/h but the Fenix 7 always showed lower speeds liek -2kmh

The Fenix 7 i used in the multiband mode..

atteched you see the results.. but what did this tell us?

The Fenix 7 is ****?

Strange. I'll compare my Fenix 7 solar with GW-60 tomorrow to check this

Today I compared Fenix 7 with GW-60 and Suunto Ambit 3 on the same route for 10 km, simultaneously and here are the max. speed data:
- Fenix 7: 85,9 km/h or 46,4 kt
- GW-60: 85,99 km/h or 46,43 kt
- Suunto: 85,3 km/h or 46,06 kt
So the Fenix 7 is very accurate.

Later I compared Fenix 7 to Fenix 6x on a 6,5 km route and found out that Fenix 6x shows 1,5% bigger max speed (42,1 km/h) than Fenix 7 (41,5 km/h).

So if you want to go faster, switch to Fenix 6X

One more thing that is seen from the screenshots is that the data field GPSTC V4 that can be downloaded from the Garmin's Connect IQ store ( apps.garmin.com/en-GB/apps/f0f3fbd5-9de3-4d69-b89b-10b76d6a9f0f) is not accurate because it shows almost 1 knot slower 2s speed (45,4 kts) compared to GW-60 (46,34 kts).

It's always good to see people comparing their results on different devices. But very little can be drawn from such a simplistic comparison of 2 sec peak speeds. The first thing that needs to be checked is that each device is actually looking at the same period of time. If a session has several similar top speeds often different devices will pick different parts of the track. The GPSTC V4 Software is neither more or less accurate than the device that it is used on. The code simply averages the best two adjacent one second results. However the code does apply some filtering. If points are missing or are hugely different to surrounding points then the 2 second peak will be reduced by a calculated factor.
I see in your post that the GPSTC V4 software has recorded 111219 accel errors. This means that 111 acceleration errors have been recorded at typical windsurfing planing speeds and 219 errors have been record at slower speeds. In a typical session I may see one or two of each type of error, generally after a fall when the watch gets submerged. Numbers like yours either indicate terrible satellite reception and/or the fact that it appears from your track you are not actually windsurfing. If you are in a car or motorbike the acceleration numbers will far exceed what is possible whilst windsurfing.
The filters in GPSTC V4 have been carefully tuned for windsurfing. Using the app for other activities may not produce the correct results.

Select to expand quote

tbwonder said..
It's always good to see people comparing their results on different devices. But very little can be drawn from such a simplistic comparison of 2 sec peak speeds. The first thing that needs to be checked is that each device is actually looking at the same period of time. If a session has several similar top speeds often different devices will pick different parts of the track. The GPSTC V4 Software is neither more or less accurate than the device that it is used on. The code simply averages the best two adjacent one second results. However the code does apply some filtering. If points are missing or are hugely different to surrounding points then the 2 second peak will be reduced by a calculated factor.
I see in your post that the GPSTC V4 software has recorded 111219 accel errors. This means that 111 acceleration errors have been recorded at typical windsurfing planing speeds and 219 errors have been record at slower speeds. In a typical session I may see one or two of each type of error, generally after a fall when the watch gets submerged. Numbers like yours either indicate terrible satellite reception and/or the fact that it appears from your track you are not actually windsurfing. If you are in a car or motorbike the acceleration numbers will far exceed what is possible whilst windsurfing.
The filters in GPSTC V4 have been carefully tuned for windsurfing. Using the app for other activities may not produce the correct results.

It was easier to compare them while driving but I tried to drive and accelerate very gently and within the range of the speed windsurfing speeds. Next time I will compare them while windsurfing.

This!!:
..." But very little can be drawn from such a simplistic comparison of 2 sec peak speeds".

We also regularly see that top 2sec speeds can vary by up to 1knot in comparison with Motion or other very accurate and verifiable devices in side by side testing. A few agreeing results dont make up for the few which are completely off (which we dont see to any significant degree in side by side testing with the truly accurate and properly verifiable devices. ie: NOT Coros, Garmin or Suunto 'watches'.

The bottom line is that those watches are great toys for on the water feedback, but don't ever rely on them being accurate all the time for competitions or comparisons with your mates.

Garmin Fenix 6 Pro half price at JB $574
www.jbhifi.com.au/products/garmin-fenix-6-pro-sports-watch-black

Select to expand quote

tbwonder said..
....
SpeedPro -Enables advanced speed metrics for windsurf activity runs.

So lots of unanswered questions.
What are the advanced metrics that Garmin are talking about?
...

Speedpro breaks your session into "Runs". For each run you get 2 second and 10 second maximum speeds. I'm not sure exactly how it works out what a Run is yet. I'm guessing it would be a period of speed bracketed by a slow bit.

When Speedpro is turned on you get a Speedpro screen in the Windsurf activity when you're riding. You can only see it when you are recording the activity.

You can see the Runs in the Connect app. Tap on the lap icon (looping arrow thingie) and it'll let you see Top 5, All Runs and All Laps. The Run data has run number, time (minutes into the session), distance and 10 second speed in knots.

You can't see the 2 or 10 second speeds in the web site.

It all seems like decent data to have, but implemented in a very half arsed way. I've sent them a list of errors in the implementation and I'm curious if they will fix it.