Lake George was a good opportunity to test out my Datafields. I Have amassed quite a bit of data.
Below is a comparison of 13 sessions at LG. All sessions are a comparison of the Original Screen Motion (upper arm) and a Garmin Fenix 5X (wrist of same arm)
Green indicates difference from Motion less than 0.25 kts, Amber 0.25 to 0.5 and Red above 0.5.



I will discuss the 6 categories individually:

The 2 Sec. I was quite happy with the performance of the two second category 7/13 results coming in at 0.25 kts or better and only 1 worse than 0.5 knots. As the Garmin only logs two data points I do not have a lot to work with. I use the Garmin "speed" variable that although is not Doppler, uses the in built accelerometer.

5*10. As you would expect the 5*10 results are even better. 11/13 less than 0.25 and the worst being only 0.4kt.

Nautical Mile. Similar to the 5*10 the nautical mile has plenty of points to work with and has produced pleasing results with 11/13 better than a 0.25 kts error.

Alpha. Studying the alpha has been puzzling and time consuming. I had a feeling that it was generally over reading compared to the Motion, but studying these 13 sessions it is clear that it is over reading in a very predictable way. But why? First step was to check my code, just to be certain, that with all the register shuffling, that something wasn't a register out of position. But everything appeared to be in order. So yesterday I performed a test with six GPSs fastened to a flat board on the front of my mountain bike. Then I cycled up and down the street doing alphas. The first two in one street and the next three in an adjacent street that has a nice wide circle at the end (Unfortunately also some large trees).



The comparison of the Big Motion, Little Motion and GW60 are very impressive with generally only 0.1 kt between measurements. The two GT31s and the Garmin also produced good results in the first two tests. I have shaded the results red in the other tests as the accuracy results from the GT31 where terrible with the sAcc up around 2 at times. Obviously I can not see sAcc for the Garmin but it is quite possibly the same. So judging by the first two alphas, it looks like the Garmin code is correct. When mounted flat on a board with good view of the sky, it appears to measure alphas very well, which is what I found when I wrote and tested the code last year. I suspect that the errors are being created by the movement of your arms during an actual gybe and changing from under arm to over arm grip. The two GTs and the Garmin recorded a significantly longer track length than the 5 and 10hz devices.
If the Garmin is always measuring the length of the alpha path slightly longer than it actually is, then I could adjust this in the code. I need to do some further testing to confirm this.

Hour. The hour produced good results with 12/13 within 0.25 kts of the Motion , the other one only 0.27 different. Interestingly the Hour results also consistently over read on the Garmin. Could this be due to the fact that it is measuring each alpha a few metres longer than it should be. After 25 or more alphas in the hour this distance adds up.





When attempting "hours" at LG, I found it difficult to read the session time which is in smaller text at the bottom of the screen. I have added a circular arc that makes its way around the screen, once the hour is complete it turns green.

Distance. The Garmin overall session distances appear to be reasonably accurate. This is not a fair comparison as at times on shore I would take the motion off and then keep walking around with the Garmin on. However I do feel it is typically measuring a little long, is it all those miss-calculated alphas adding up?

I would welcome any comparison data between My Garmin Datafields and any Motion device. The more data I can collect the better.
It is possible that different Garmin watches have different reception issues, so I cam keen to see some data from other watches. I am particularly interested in the 245 Music, as that is the watch I recommend the most often.

Really appreciate all the effort you are putting into the Garmin software Andrew. It is a great feature and I like looking at the scores on the beach!

Great work TB
What program are you using to analyse the garmin tracks. Garmin Connect or KA72??

the garmin alpha on 18/02 should be orange not red.

Maybe try and wear your garmin on the helmet facing up to investigate the reason for the greater errors during jibes.

Select to expand quote

tbwonder said..
Lake George was a good opportunity to test out my Datafields. I Have amassed quite a bit of data.
Below is a comparison of 13 sessions at LG. All sessions are a comparison of the Original Screen Motion (upper arm) and a Garmin Fenix 5X (wrist of same arm)
Green indicates difference from Motion less than 0.25 kts, Amber 0.25 to 0.5 and Red above 0.5.



I will discuss the 6 categories individually:

The 2 Sec. I was quite happy with the performance of the two second category 7/13 results coming in at 0.25 kts or better and only 1 worse than 0.5 knots. As the Garmin only logs two data points I do not have a lot to work with. I use the Garmin "speed" variable that although is not Doppler, uses the in built accelerometer.

5*10. As you would expect the 5*10 results are even better. 11/13 less than 0.25 and the worst being only 0.4kt.

Nautical Mile. Similar to the 5*10 the nautical mile has plenty of points to work with and has produced pleasing results with 11/13 better than a 0.25 kts error.

Alpha. Studying the alpha has been puzzling and time consuming. I had a feeling that it was generally over reading compared to the Motion, but studying these 13 sessions it is clear that it is over reading in a very predictable way. But why? First step was to check my code, just to be certain, that with all the register shuffling, that something wasn't a register out of position. But everything appeared to be in order. So yesterday I performed a test with six GPSs fastened to a flat board on the front of my mountain bike. Then I cycled up and down the street doing alphas. The first two in one street and the next three in an adjacent street that has a nice wide circle at the end (Unfortunately also some large trees).



The comparison of the Big Motion, Little Motion and GW60 are very impressive with generally only 0.1 kt between measurements. The two GT31s and the Garmin also produced good results in the first two tests. I have shaded the results red in the other tests as the accuracy results from the GT31 where terrible with the sAcc up around 2 at times. Obviously I can not see sAcc for the Garmin but it is quite possibly the same. So judging by the first two alphas, it looks like the Garmin code is correct. When mounted flat on a board with good view of the sky, it appears to measure alphas very well, which is what I found when I wrote and tested the code last year. I suspect that the errors are being created by the movement of your arms during an actual gybe and changing from under arm to over arm grip. The two GTs and the Garmin recorded a significantly longer track length than the 5 and 10hz devices.
If the Garmin is always measuring the length of the alpha path slightly longer than it actually is, then I could adjust this in the code. I need to do some further testing to confirm this.

Hour. The hour produced good results with 12/13 within 0.25 kts of the Motion , the other one only 0.27 different. Interestingly the Hour results also consistently over read on the Garmin. Could this be due to the fact that it is measuring each alpha a few metres longer than it should be. After 25 or more alphas in the hour this distance adds up.





When attempting "hours" at LG, I found it difficult to read the session time which is in smaller text at the bottom of the screen. I have added a circular arc that makes its way around the screen, once the hour is complete it turns green.

Distance. The Garmin overall session distances appear to be reasonably accurate. This is not a fair comparison as at times on shore I would take the motion off and then keep walking around with the Garmin on. However I do feel it is typically measuring a little long, is it all those miss-calculated alphas adding up?

I would welcome any comparison data between My Garmin Datafields and any Motion device. The more data I can collect the better.
It is possible that different Garmin watches have different reception issues, so I cam keen to see some data from other watches. I am particularly interested in the 245 Music, as that is the watch I recommend the most often.

Andrew this edge light that indicates hour is gold.
Idea , could the colour be green while your hour is improving and red or orange to indicate partial or complete hour. I found the hour readings for the app the most appealing .

Select to expand quote

tbwonder said..
Lake George was a good opportunity to test out my Datafields. I Have amassed quite a bit of data.
Below is a comparison of 13 sessions at LG. All sessions are a comparison of the Original Screen Motion (upper arm) and a Garmin Fenix 5X (wrist of same arm)
Green indicates difference from Motion less than 0.25 kts, Amber 0.25 to 0.5 and Red above 0.5.



I will discuss the 6 categories individually:

The 2 Sec. I was quite happy with the performance of the two second category 7/13 results coming in at 0.25 kts or better and only 1 worse than 0.5 knots. As the Garmin only logs two data points I do not have a lot to work with. I use the Garmin "speed" variable that although is not Doppler, uses the in built accelerometer.

5*10. As you would expect the 5*10 results are even better. 11/13 less than 0.25 and the worst being only 0.4kt.

Nautical Mile. Similar to the 5*10 the nautical mile has plenty of points to work with and has produced pleasing results with 11/13 better than a 0.25 kts error.

Alpha. Studying the alpha has been puzzling and time consuming. I had a feeling that it was generally over reading compared to the Motion, but studying these 13 sessions it is clear that it is over reading in a very predictable way. But why? First step was to check my code, just to be certain, that with all the register shuffling, that something wasn't a register out of position. But everything appeared to be in order. So yesterday I performed a test with six GPSs fastened to a flat board on the front of my mountain bike. Then I cycled up and down the street doing alphas. The first two in one street and the next three in an adjacent street that has a nice wide circle at the end (Unfortunately also some large trees).



The comparison of the Big Motion, Little Motion and GW60 are very impressive with generally only 0.1 kt between measurements. The two GT31s and the Garmin also produced good results in the first two tests. I have shaded the results red in the other tests as the accuracy results from the GT31 where terrible with the sAcc up around 2 at times. Obviously I can not see sAcc for the Garmin but it is quite possibly the same. So judging by the first two alphas, it looks like the Garmin code is correct. When mounted flat on a board with good view of the sky, it appears to measure alphas very well, which is what I found when I wrote and tested the code last year. I suspect that the errors are being created by the movement of your arms during an actual gybe and changing from under arm to over arm grip. The two GTs and the Garmin recorded a significantly longer track length than the 5 and 10hz devices.
If the Garmin is always measuring the length of the alpha path slightly longer than it actually is, then I could adjust this in the code. I need to do some further testing to confirm this.

Hour. The hour produced good results with 12/13 within 0.25 kts of the Motion , the other one only 0.27 different. Interestingly the Hour results also consistently over read on the Garmin. Could this be due to the fact that it is measuring each alpha a few metres longer than it should be. After 25 or more alphas in the hour this distance adds up.





When attempting "hours" at LG, I found it difficult to read the session time which is in smaller text at the bottom of the screen. I have added a circular arc that makes its way around the screen, once the hour is complete it turns green.

Distance. The Garmin overall session distances appear to be reasonably accurate. This is not a fair comparison as at times on shore I would take the motion off and then keep walking around with the Garmin on. However I do feel it is typically measuring a little long, is it all those miss-calculated alphas adding up?

I would welcome any comparison data between My Garmin Datafields and any Motion device. The more data I can collect the better.
It is possible that different Garmin watches have different reception issues, so I cam keen to see some data from other watches. I am particularly interested in the 245 Music, as that is the watch I recommend the most often.

Andrew this edge light that indicates hour is gold.
Idea , could the colour be green while your hour is improving and red or orange to indicate partial or complete hour. I found the hour readings for the app the most appealing .

Andrew ,do you have a go fund me Page or similar ,i would chip in

Great idea for the hr.I suggested a clockface that showed up occasionally so you knew how much longer you had to sail. This does the same job and takes less space.

excellent idea

Select to expand quote

TRIMMER said..
Andrew ,do you have a go fund me Page or similar ,i would chip in

I have had quite a few offers for funding. However it is not something I am seeking.
Many people have done many great things for our sport without any funding. GPSTC is a great example of that.
Everyone can contribute something. People have different personalities and skills, some folk hold positions at the local club, some organise competitions or man the rescue boats. Others help out with training or step in to offer advice to beginners.
Some are very handy at helping with repairs.
Some spend there time answering the same old questions on Seabreeze.
I've written a bit of code for a watch, it is a small contribution. I have enjoyed doing it and made a few new friends as well.

I have updated the following Datafields to V2.0

GPSTC field 1 (Fenix3, FR230,235,630,735XT, 920XT)
GPSTC field 2 (Fenix3, FR230,235,630,735 Only)
GPSTC field 1 with Alpha 500
GPSTC field 2
GPSTC Field 1 Speed Version

Following testing at LG and input from several other users I have made the following changes.

Adjustment to the way the distance is calculated during an "Alpha". This has been tuned for alphas above 16 kts, so don't expect accurate results for slow alphas. The flow on effect of the "Alpha" adjustment is that the "Hour" reading will also be slightly lower. Which I believe will bring the results even closer to those reported by Motion devices.

I have added acceleration filtering. This should removed spikes, that can badly impact especially 2 sec accuracy.
The number of times the filter is applied is written to Garmin Connect. Most issues are when stationary (perhaps under water or whilst getting something out of the car) So I have two counts, I add 1 for each time the filter is applied and then 1000 if it is applied when travelling above 13 kts. So if you see the number 2007 in Garmin Connect you know the filter was applied 7 times during the session and 2 of those times it was applied at speeds over 13 kts.

Three of the Datafields modified are now at 100% memory usage. I have had to deleted all the letters from the fonts that are not used to save a few crucial bytes. I strongly recommend that anybody buying a Garmin watch specifically for these Datafields should be looking at watches with at least 64k Datafield memory, that means Garmin 245 Music or better.

Lots of changes - Only a small amount of testing - There could be issues - You get what you pay for

Select to expand quote

tbwonder said..

TRIMMER said..
Andrew ,do you have a go fund me Page or similar ,i would chip in

I have had quite a few offers for funding. However it is not something I am seeking.
Many people have done many great things for our sport without any funding. GPSTC is a great example of that.
Everyone can contribute something. People have different personalities and skills, some folk hold positions at the local club, some organise competitions or man the rescue boats. Others help out with training or step in to offer advice to beginners.
Some are very handy at helping with repairs.
Some spend there time answering the same old questions on Seabreeze.
I've written a bit of code for a watch, it is a small contribution. I have enjoyed doing it and made a few new friends as well.

Thank you Andrew.

Excellent work Andrew, i bought a garmin watch just for your apps.top stuff

The Garmin with your data fields is a game changer
Every one who has used it would agree I am sure.
thank you very much.

V2.1 of the Speed Version of Datafield 1 released today (Only for large memory watches)

I have found the slow automatic screen scrolling to be a bit annoying when trying to read things whilst sailing.
So now it works as follows.
1: When stationary or moving less than 5kts. The datafield scrolls between "2 sec" screen, "Alpha" Screen and "Speed Graph" screen
2: When travelling between 5 kts and the user set "Speed Display" speed the datafield will scroll between the"2 sec" screen and the "Alpha" Screen
3: When travelling above the user set "Speed Display" speed only the "Speed Graph" screen will display.
I have also slightly shortened the period of time that the Live alpha screen appears. It now displays when you are within 100m of the start point of the alpha.
I have thickened up the line on the speed graph ,to make it easier to see whilst sailing.

It's been nearly a year now since I kicked off this project. It has slowly developed from a single number on a page to what it is now. There are 6 different Datafields for a range of watches, with a wide range of features suggested by various people along the way. I just kept adding bits and squeezing things in.
It's raining and I'm stuck inside so the time has come for a complete rethink.
Here is my wish List:
1. To display the screen I want to see when I want to see it without the need to push buttons.
2. Larger text so easier to read on the move without glasses.
3. Live Nautical Mile as well as "Best run" Nautical, so you know when to ease up.
4. A way of knowing when to keep going in the hour - to improve your hour.
5. Put all the code into one Datafield to make management easier
6. Simplify some of the code by removing some stuff that I don't really use.

Constraints:
1. There is no way to directly change pages within a Datafield by using the watch buttons.
2. Memory space is very limited
3. Only 8 records can be written from a single Datafield to Garmin Connect. (Currently 12 are written from the 2 Datafields)
4. I am only a programming hack - I don't really know what I am doing.

The Negatives
To achieve the wish list items there will the following downsides.
1. The Datafield will only be suitable for modern music/maps watches with round screens (Garmin 245Music and up)
2. Can't write the five individual 5*10 runs to connect - Only the average 5*10
3. No more GPS accuracy logging - it was pretty well useless data anyway.
4. Removal of 60 and 70 metre alphas - Couldn't find a good place to put these, I don't really ever look at them as the live alpha screen keeps you informed of the separation distance
5. The session distance will no longer be displayed and the session time is only displayed on the Hour page. This is easy to display on other screens outside my Datafield. Perhaps a screen with Time of day, Session Time and Session Distance.
6. Ability to reverse the foreground and background colours removed - It will be black letters on white background.

Below is a diagram of what I am thinking. The datafield will altenate between the "Best" and "last" screens. The best can be easily picked by the background color. Then under user defined conditions the Datafield will switch to the other pages. The exception being the "Hour" page which will be accessed by pushing the "lap" button.

Next step - finish coding and some testing.

What you've created already is pretty good! The reasons/wish list makes sense but you know we don't like too much change at once . The negatives listed aren't too serious but it's nice to have the distance on the main screen, can you keep that?

Select to expand quote

Dezza said..
What you've created already is pretty good! The reasons/wish list makes sense but you know we don't like too much change at once . The negatives listed aren't too serious but it's nice to have the distance on the main screen, can you keep that?

I know you don't like change Dezza, otherwise you would be foiling by now!
Worry not, the existing Double Datafields will remain unchanged due to memory restrictions in most watches. I will continue to support them. This new one will perhaps ultimately replace the Current "Datafield 1 Speed Version", Which I don't think you are using because I think you have the Fenix 6S which doesn't support it.
Saying that, trying to recall which watches different friends have is stretching my memory at times. It would be nice if Garmin released 1 new watch each year rather than 20.

The only things I want to see out on the water, on one screen, are distance, max speed of the session, and time of day. Fenix 5x. I do need to upload the track(s) at the end of the day for archiving.

I don't know whether I need tbwonder's excellent datafields for just these things. Can someone guide me on this?

Select to expand quote

4. A way of knowing when to keep going in the hour - to improve your hour.

When your current hr is the same as the best Hr keep sailing till your knackered or the current HR falls below your best HR

Select to expand quote

YP1 said..

4. A way of knowing when to keep going in the hour - to improve your hour.

When your current hr is the same as the best Hr keep sailing till your knackered or the current HR falls below your best HR

I am usually knackered well before the first hour is complete. So I am always looking for an excuse to stop.

I was thinking of displaying the average of your last 10 minutes. Then say after 60 minutes if the last 10 minute display is better than your "Best Hour" then it may be worth pushing on, or if significantly worse then it may be the time to give up.

Select to expand quote

tbwonder said..
It's been nearly a year now since I kicked off this project. It has slowly developed from a single number on a page to what it is now. There are 6 different Datafields for a range of watches, with a wide range of features suggested by various people along the way. I just kept adding bits and squeezing things in.
It's raining and I'm stuck inside so the time has come for a complete rethink.
Here is my wish List:
1. To display the screen I want to see when I want to see it without the need to push buttons.
2. Larger text so easier to read on the move without glasses.
3. Live Nautical Mile as well as "Best run" Nautical, so you know when to ease up.
4. A way of knowing when to keep going in the hour - to improve your hour.
5. Put all the code into one Datafield to make management easier
6. Simplify some of the code by removing some stuff that I don't really use.

Constraints:
1. There is no way to directly change pages within a Datafield by using the watch buttons.
2. Memory space is very limited
3. Only 8 records can be written from a single Datafield to Garmin Connect. (Currently 12 are written from the 2 Datafields)
4. I am only a programming hack - I don't really know what I am doing.

The Negatives
To achieve the wish list items there will the following downsides.
1. The Datafield will only be suitable for modern music/maps watches with round screens (Garmin 245Music and up)
2. Can't write the five individual 5*10 runs to connect - Only the average 5*10
3. No more GPS accuracy logging - it was pretty well useless data anyway.
4. Removal of 60 and 70 metre alphas - Couldn't find a good place to put these, I don't really ever look at them as the live alpha screen keeps you informed of the separation distance
5. The session distance will no longer be displayed and the session time is only displayed on the Hour page. This is easy to display on other screens outside my Datafield. Perhaps a screen with Time of day, Session Time and Session Distance.
6. Ability to reverse the foreground and background colours removed - It will be black letters on white background.

Below is a diagram of what I am thinking. The datafield will altenate between the "Best" and "last" screens. The best can be easily picked by the background color. Then under user defined conditions the Datafield will switch to the other pages. The exception being the "Hour" page which will be accessed by pushing the "lap" button.

Next step - finish coding and some testing.

Looks great Andrew...
Can't believe it's a year since I was walking up and down the street and driving around the block to test the first version.
Looking forward to it!!

How current is the app? I'm looking for a device&app to wear besides my motion. Which Garmin watch can run the app.? cheers Dave

Select to expand quote

BSN101 said..
How current is the app? I'm looking for a device&app to wear besides my motion. Which Garmin watch can run the app.? cheers Dave

See list on this page.

www.seabreeze.com.au/forums/Windsurfing/Gps/Garmin-GPSTC-Datafield-to-complement-the-Motion-Simple-Logger?page=7

How do I update to make sure I have the latest datafields? I've got a Garmin Forerunner 245 music.

Select to expand quote

sboardcrazy said..
How do I update to make sure I have the latest datafields? I've got a Garmin Forerunner 245 music.

Do they update automatically or do I need to download something?

Hi Andrew, don't know anything about software etc but i managed to pick up a coros apex pro watch which has all the GPS Speed sailing fields already installed, is there any reason you couldn't use that software on the Garmin watch?

Select to expand quote

choco said..
Hi Andrew, don't know anything about software etc but i managed to pick up a coros apex pro watch which has all the GPS Speed sailing fields already installed, is there any reason you couldn't use that software on the Garmin watch?

more importantly ! will you be able/allowed to post on gpstc ?
serious question, they allow it on gpsspeedsurfing.

The new Garmin Fenix & Epix 7 will have this on the watch as a factory default setting +

"- Added new Windsurf Sport Type
- Added new SpeedPro function for Windsurfing (primarily for speedsurfers)"

www.dcrainmaker.com/2022/01/garmin-fenix7-7s-7x-in-depth-review.html

Select to expand quote

choco said..
Hi Andrew, don't know anything about software etc but i managed to pick up a coros apex pro watch which has all the GPS Speed sailing fields already installed, is there any reason you couldn't use that software on the Garmin watch?

Not possible, the Garmin app platform is not compatible with Coros