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I'm trying something a bit different, still 2 boards, but they look quite small.
www.aliexpress.com/item/32790658678.html?spm=2114.12010108.1000023.9.35d7613fbLiEto
This is a charger and booster combined.
And this is the protection board.
www.aliexpress.com/store/product/3-7V-4-2V-3A-Li-ion-Lithium-Battery-Charger-Over-Charge-Discharge-Overcurrent-Protection-Board/1525466_32803131082.html?spm=2114.12010612.0.0.mlFzON
I've never dealt with aliexpress before, so it will be interesting to see what I eventually get and how it works.
Can an existing GPS be hacked to make it better rather than starting from scratch. Make a good one great by tweaking some part of it or stealing from others. Like Canmore with a large readable screen. An older GT-XX with bigger card or the watch that doesn't break.
When the diy ones are sorted I'll be forking out to get one, over the production GPS units that have short comings.
GREAT work to all involved
Unless you're a top gun hacker, improving an existing unit would be extremely hard if not impossible.
I don't think anybody is going in to production, but I don't mind helping a bit with the build, as you say once we get it sorted.
Look forward to seeing your display results Formula, it's obviously a big advantage for people who only want one device.
I had another session yesterday, so I've been doing more number crunching for approval.
I got the last one a bit wrong, summing the +/- numbers isn't correct, we need to see that there is an overlap between possible speeds.
Yesterday I was wearing a loose spray jacket, so the logger slipped around a bit on my arm, possibly why there isn't the same runs in the top 25.
So they all overlap, although I had to check the 13:44:54 run to make sure.
You can see above why I do a time sort first, (the 18s difference doesn't help) but it makes sure the same runs are compared. If it's left in a speed format, you can easily be comparing different runs.
Thanks Peter, I checked again and found I was right the first time, don't know what I did the second time, to get a different result.
Anyway, Daffy is the man to talk to.
Because of the missing result at 13:31 and out of interest, I've added the GW60 to the 10s comparrisons.
That also has 13:31:34 missing. Looking at the speed graph, they all have about the same Max speed at that point, but the GW52, has it for longer. And strangely the watch has the best SDoP and the GW52 the worst?
GW52 on Left, (on head). GW60 in middle, (on wrist of course). and logger at right (on upper right arm)
Not quite what you'd expect. And isn't reflected in the other results.
I hadn't bothered including the watch in these comparisons, as I thought the watch on my head was always going to be more accurate. Looks like that isn't always the case. So future comparisons will be a 3 way affair.
And I'll arrange the table with the logger in the middle so I can use 2 difference columns
Hmmm, I didn't check the GW52 data at 13:49, I was more concerned with the logger missing the 10s at 13:31.
I'll go and check the GW52 now. Back soon.
Yep, spot on Peter.
GPSResults filters ignore intervals with missing points. unticking filters brings it back in, but the GW52 has gone down to 4 sats So the missing data points are probably due to loss of sats, why that should happen to the unit on my head but not the ones on arm and wrist is a puzzle?
I think I have a theory, I run the paqua armband over the top of the pouch on my helmet. I position the GW52 so the antenna isn't under the armband, but if it moves around, I'm fairly sure a wet salty band would kill the sat signal.
There's a 36s gap in the GW52 data, just before it starts coming back with 4 sats. It looks like it started while I'm walking upwind, was I resting the sail on my head?
Anyway, I'm trying to work out a way of mounting without the armband on top.
Interesting that a wet armband on top of the GPS might kill the signal so much. You are quite good at finding things that can go wrong!
On occasion, I have observed similar problems with Locosys units worn on my arm or wrist, without any apparent reason (like crashes, swims, etc.). There'd be multi-second gaps in the middle of the run, followed by shorter stretches with a marginal number of satellites. The only times I noticed this was when I was comparing GPS units, or when I also used GPSLogit and the GPS display would not show the speeds I heard, so I'd look closely. Not sure this is what's going on in your case, just thought I'd mention it.
Yes the worry is, if I'd only had the GW52 on my head, I would have assumed the missing data was from a crash, where I'd gone under water, because I have stopped there.
I'll do some tests and see just how much a salty wet armband over the antenna affects the signal.
I've just started to make a cap for my helmet, that hopefully will hold both units. Still very much in the development phase at the moment. If I can get it to work I'll post some pics.
Haven't done any wet armband tests yet, but ot be on the safe side. I packed the GW52 into the paqua midi so it couldn't move, and the antenna stayed well clear of the armband. I have it doubled over the paqua, and it's a soft absorbent material, so I wouldn't be surprised if it totally kills the sat signal once full of saltwater.
It was only a short session yesterday, too choppy and not much fun, but I did get some interesting results.
Lots of gaps in the spread sheet, all at low speed. I'm not really sure what's causing this. The speed graphs look very similar, I see no reason for the difference, unless it's got something to do with the, "one per run" rule. Because to me they seem to be on the same run, speed doesn't drop to 0 and there's no gybe, so maybe, if speed drops below 5kts, that triggers a new run?
More investigation needed.
However, all the results are again very close, and no strange loss of signal with the GW52
More data today.
A bit choppy for me when the wind blew, and not enough wind when the water smoothed out a bit. So although no fantastic speeds, I did manage some 10s runs faster than 5kts.
So no gaps, and all the accuracy envelopes overlap. The watch has the biggest differences, but that's to be expected with the underhand grip, and smaller antenna.
The differences are significantly better after 14:15. It was mainly stormy today, but with some small sunny periods, so could this be weather related? It doesn't seem to be reflected in the accuracy data.
I have been following this thread with intense interest.
Mike has done a great job of construction and testing.
Peter has contributed invaluable knowledge, research and testing.
Well done to both of you.
It is obviously time to publish a formal Validation/Approval process for the use of these DIY ublox M8 based GPS devices on GPS Team Challenge for those who wish to do so.
Mike has fullfilled the process we have in mind in this thread for all to see
Stay tuned (while we dot the i's and cross the t's), for an announcement and documetation very soon.
Thanks Andrew!
It's been an interesting and informative journey, if a bit frustrating at times.
But ending up with a logger, with a more accurate and longer recording time is very satisfying.
Great effort Mike!
I got stuck with a cheap Chinese Ublox with old firmware I could not upgrade. I have no GW52 (or similar) to compare it to.
Having a UBLOX approved will prove any genuine UBLOX (eg Drotek) is good enough for what we need and that even some Chinese UBLOX units are good enough to get approved 
Just a point regarding adding DCDC power supplies to the units is these DCDC supplies will introduce noise to the system and that MAY (or MAY NOT) effect the performance of the Ublox module. It would make sense that if one is using a DCDC power supply module then it should be used when producing results for the approval process.
An alternative that could be considered if someone does not have a GW52/60 would be to accept data from two separate ublox 8 units, perhaps together with GT31 data if someone only has a GT31. If there are any issues with the build or the chips used, they should show up as differences. Furthermore, problem units would be likely to have high sAcc values. Cost per unit could be around $40-$50, so building 2 is still quite reasonable.
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I managed a few half decent alphas Monday, wind was light when water flat, and choppy when wind picked up, so nothing great.
But it did throw up a difference between the logger and GW52 that has no overlap in the accuracy envelopes. A 0.111kt difference but only a 0.93kt combined envelope. Both alpha results look very good, I can't pick a problem with either of them.
So again, I've referred to the watch. This is only different to the logger by 0.01kt and different to the GW52 by 0.121.
With GW52 on head, logger on right arm and watch on right wrist, this could be a genuine difference between head and arm movements in the gybe.
The dual head mount is coming on, I'll get a better understanding once both antennas are side by side on my head.
The first result is the worry, all the rest are fairly close. the difference could be the way I sometimes throw the sail over in the gybe.
The difference is about 0.1 knots, which is still pretty good. I'd expect the accuracy of the GT-31 in alphas to be a lot worse due to the heavy filtering in the device.
The "error envelops must overlap" approach is great for 2 and 10 seconds, but it has its limitations when you go to longer times. If you look at nautical miles or 1 hour results, you will find that the ranges often do not overlap. That just shows that errors are not completely independent over longer time periods, so that the assumption that errors average out is not completely valid anymore. The alpha in question is a 45 second long run; longer periods give you a higher chance of picking up regions where the error is biased. That bias would have to be only +0.02 knots in the GW-52 data to get the non-overlap.
You may be measuring a real speed difference. With the GW-52 was on the top of your head and the watch and logger were on the inside arm in a jibe, the radius and therefore speed would be marginally slower . If that theory is correct, then your watch arm would have been outside on the second alpha, and inside on #1, 3, and 4. Would match the times if your runs were about 1.5-2 km long...
