Pascal on Fb talking accuracy for his 2024 Speed Comp.

Today, GPS timing is not precise enough. This is why I am now mobilizing, with the help of the French company McLloyd, to develop a cutting-edge tracker, connected to the RTK network. The advantage is that we will be able to have accuracy to within 2 centimeters, whereas a GPS that you buy commercially is accurate to 30 meters.

www.facebook.com/windmag

Really ?. I thought GPS L1 with modern processing can do a bit better than that. Plus, receivers don't just receive/decode GPS system only now days.

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Te Hau said..
Pascal on Fb talking accuracy for his 2024 Speed Comp.

Today, GPS timing is not precise enough. This is why I am now mobilizing, with the help of the French company McLloyd, to develop a cutting-edge tracker, connected to the RTK network. The advantage is that we will be able to have accuracy to within 2 centimeters, whereas a GPS that you buy commercially is accurate to 30 meters.

www.facebook.com/windmag

I think maybe Pascal is missing some technical background here, the McLloyd's trackers are also logging at 10Hz, so comparable to Motion / ESP-GPS / SailMon trackers, results from Luderitz, where in the early years video was one on one compared to uBlox loggers it was spot on.

RTK doppler speed is not better then normal GPS. RTK position accuracy is way better (2 cm ) then normal GPS (50 - 100 cm). Theoretical, the calculated speed distance/time could be better then doppler speed.

50 - 100 cm is a bit different than 30 meters as claimed in the article .......

He is very wrong.

Consumer 'GPS's', even those that use multiple satellite systems, are capable of a few meters and better of positional accuracy. This is not very accurate for speed measuring in the way windsurfers want, but it is almost an order of magnitude better than he claims.

Tests I helped Manfred Fuchs run at Luderitz in 2013, comparing his twin Ublox 6 based GPS's to the timing gear results showed remarkably close correlation to the official results.

Manfred tested much more modern, Multi GNSS devices (I think ublox 9 based) last year and he reported to me that first impressions were that it looked like they were extremely close to the official results.

There is an abundance of data and papers on the web about the speed accuracy of the higher quality Doppler based consumer devices. There is little sense in going to highly complicated and expensive RTK technology to use positional data that would be unlikely to be any more accurate in determining your speed over ground (or water in this case . )

From the McLloyd website:

A pack of 5 sports devices with software and vests with a 20% discount costs $7200. (Presumably this US$ - about $11,169 Australian Dollars! So over A$2000 each.

I suggest that this is something that your average sailor, even dedicated speed enthusiasts, are likely to balk at.

Of course, he is talking about 'Events' where presumably the event organiser leases the pack of 5 devices for a Month (and adds that cost to the entry fee of course) for around US$300 (A$465), or about A$93 each sailor. That's a pretty stiff add-on to an entry fee which would likely be in the hundreds of dollars on top of that, but probably doable.

Accuracy? A quick perusal of some recent comparative testing between a Motion and a ESP device chosen at random from my files shows this:

UBLOX 8 based Motion on the left, Ublox 10 based ESP on the right.

Columns: distance, run, speed device 1, error calculation, time at start of run. Speed device 2, error calculation, time at start of run.

For device one the error is in the order of around 0.03 Knots. For device two it is around 0.02 knots.

Note that none of the runs differ by more than the reported error margin. A couple by significantly less!

This comparison is very simplistic (There is a great deal that of discussion that can be had about putting meat on the bones of those calculations and comparisons) but for a simple comparisons sake:

0.03 Knots = 0.0154 m/sec, or simplistically, an error of 1.54 cm.

We could argue we already have the equivalent of sub 2cm speed accuracy from our best Doppler devices.

And for a cost of as little as US$100, or less!

Yes, we could have some very long and interesting discussions about what those error numbers mean etc, but the real world tests (like the example above) bear them out remarkably well.

On top of that, tests done directly comparing GNSS devices against offical camera timing devices over 500m also confirm this data.

and if you use 2 esp units one each side of the boom and average them, the accuracy must get even better, but don't ask me to calculate just how much better.