Garmin 920XT Windsurfing activity

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N1GEL said..

mathew said..

Just for clarity, are you are ok with me using an old Foretrex 101, which would randomly add 1.5kn greater speed to my run - so that I bettered your score?

To clarify, I don't actually care what you do. My definition of "fun" is competing against my own scores, improving my skills and, most importantly, socializing with other GPSTC members.

If you are only competing against your own scores, why are are posting to the GPSTC ? ... T = team, C = Challenge

So if you're lucky enough to have a location with a 2 knot current in your favour, that's OK as long as you are accurate to .0x of a knot?

That would make for a few places up the ladder??

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mathew said..


The big deal is 25.91 vs 26.06 ... is about 7 places in the GPSTC ranking.

that's only for one session, won't change the rankings as you say.

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N1GEL said..

sailquik said..
As it stands, all the watches, by necessity of form, use a tiny antenna (like phones)

The Suunto Ambit has a comparatively large antenna... that's the big chunky thing hanging off the side of the watch. I thought the antenna was so big it was pretty ugly and that's why I changed to the Fenix 3.

It's still quite small compared with dedicated GPS devices. It is most likely the same size as, or very similar to what they use for phones. (How big is the antenna on the Garmin Fenex? And where is it located?)

Also consider this: One of the reasons we rejected the Locosys prototype made in watch form is that the very small antenna was located in the watch band. If you sail with an underhand grip on the front hand like most windsurfers do, the watch is now under the arm facing down at the water where it will only get multipath signal which is known to completely destroy accuracy.

The bottom like is that all of these things, and many more, have been taken into careful consideration by people who understand the technology and requirements, when decisions about what is suitable for posting are made.

If a few people, lucky enough to have the large amount of surplus funds to buy a GPS watch that costs many times the price of the approved devices want to have the device approved for use, it might be possible to do enough careful, proper scientifically based testing to find out if it is just OK enough to be accepted in some specific circumstances. None of the tech crew are willing to shell out thousands of dollars to buy the multiple devices required, or willing to put in the hundreds of hours of testing to possibly come up with a results that still may be negative, for the very few people who, if they can afford to buy this device, can quite clearly afford to also buy the far cheaper approved device for posting. And even if, in the unlikely event that we did get a positive result in testing, they may bring out a new model next year and we would have to start all over again. It does not make much sense does it?

So if you like the device and want to use it for your own enjoyment and on water feedback, great for you! But please respect the competition by using an approved device for posting.

Back to the intent of this thread ...

Fin, I just downloaded your Max speed in knots datafield. Terrific! and you can choose the number of seconds too!
It seems that to add it to my Windsurf profile, I have to remove your other datafield. I want them both!
Is it possible to have them both running on different data screens.
Great work

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fin151 said..
Stretchy: you can have up to 2 datafields in a activity profile, so you should be able to have both in the same profile. You can have the Windsurfing datafield on one screen with the 1-field layout for example and the max. speed in knots datafield on another screen with a 4-field layout for example together with other stuff.

Ok, thanks Fin. I'll keep fiddling with it.....

Just to add an experience I had today to the discussion.
I had been unable to work out how to get the Canmore 102 to work ie give me a FIT file of my sail.
As I was running the racing today I asked a gentleman who knows about Canmores how to make it work.
I was duly instructed and started it up and put it in my pocket. I then started my GT31 and put it in my pocket as well.
Things got hectic with starting the racing and I forgot about the GPSs. Came back to shore and remembered them so I turned them off.
When I got home I connected the Canmore and got the FIT file and checked it on KA72 and looked at the track and it looked ok. At last I had made it work.
Then I put the SD card from the GT31 in the computer. 57 separate SBN files with numerous SDP files. Mmmmm.
That tells me the Aerial in the Canmore is more sensitive than the one in the GT31?

Hey Fin. Are you going to make a 2 sec max for the whole session, rather than just the last 1, 2 or 10 seconds? Ta.

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fin151 said..
Hi Nigel,

I made that one: apps.garmin.com/en-US/apps/1827bfb4-32f2-4ad1-ae12-f0c01d661f01

It can be configured with Garmin Express to show the max 1s, max 2s or max 10s of the whole session. On my own watch I conf'd it to show max. 2s in knots.

Configuring is very easy. In Garmin Express just click the "Manage Apps" button and scroll down to the "Max. Speed in Knots" datafield. On the right side of "Max. Speed in Knots" is a small button with 3 dots "...". Click it and choose 2s instead of 1s. Once configured you can forget about it.

used it yesterday. Works great!

Hey Fin. I get an IQ error (with a yellow exclamation mark) on my device when I set any datafield to your max speed datafield. The error shows in the field when I start an activity. Other unexpected behavior is in Apps Setting when I do set a field to max speed it looks fine. If I exit out of Apps Settings and go back into App Settings again, the field is replaced with Timer (although the error shows when an activity is initiated). I'm running software version 6.50. I've tried uninstalling both apps and reinstalling, but still got the error. I also deleted the activity, which was based on Other, but that didn't work either. I can send you the exact steps to replicate if I'm not being clear enough. Cheers. Nigel

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mathew said..

GeoffS said..
Just to add an experience I had today to the discussion.
I had been unable to work out how to get the Canmore 102 to work ie give me a FIT file of my sail.
As I was running the racing today I asked a gentleman who knows about Canmores how to make it work.
I was duly instructed and started it up and put it in my pocket. I then started my GT31 and put it in my pocket as well.
Things got hectic with starting the racing and I forgot about the GPSs. Came back to shore and remembered them so I turned them off.
When I got home I connected the Canmore and got the FIT file and checked it on KA72 and looked at the track and it looked ok. At last I had made it work.
Then I put the SD card from the GT31 in the computer. 57 separate SBN files with numerous SDP files. Mmmmm.
That tells me the Aerial in the Canmore is more sensitive than the one in the GT31?

Nope. The GT31 may or may not be less sensitive [ it appears to be equal, but nobody really knows ], but that has nothing how many files are created.

The GT31 will only create multiple files, if you have configured it to do so -> thus conversely you should have it configured for one file only.

Appreciate what you say Mathew, however for the last 2 weeks the GT31 without my doing anything other than turn it on, has recorded a single file as it has done for 2 or more years. In all of those cases it was on my arm in a bag. Only time it has created so many SBN and SBP files was the week it was in my pocket when I was running the regatta. So none of the settings have changed or have been changed.
So, if it isnt aerial sensitivity or size, then what else?

Hi Fin,
are you able to confirm if the 920XT logs 1hz doppler data yet? This seems to be a bit of a stumbling block as to this devices inclusion as being acceptable in the GPSTC.
Also, are there any users who happen to use both the 920 and GT31 at the same time who are happy to send both files through to the GPSTC tech heads so we can compare the files? This will help in aiding accuracy also.
Thanks.

Thanks fin.
To me, decrepit at westnet dot com dot au, obviously correctly formatted. I'll pass them on to sailquick as well, and anybody else who's interested.

The more comparisons we make, the better idea we'll have.

Yep, I've got them but haven't looked at them yet.
If anybody else is interested just PM me your email address, and I'll post them on.

EDIT!!!!!!!!!!!!! just noticed there is doppler data for the watch, but it has some very big 137kt spikes, strange they're all identical.

Deleting my results until I'm more sure of what I'm doing, the doppler results are giving me much worse 2s than the trackpoints.
Maybe the underhand effect showing it's hand.