Hope for a GPS alternative

Sound like a loose wire in your phone. My old iPhone had similar problems with the GPS, and later with WiFi.

The three dongles I got all work fine (no real surprise if 9 out of 10 work). So do the two phones. Everything together still cost less than one GW-60. But I've had only test drives and a few windsurf sessions so far. In today's session, the dongle numbers where closer to one GW-60 than the numbers from the second GW-60 which was on the other arm. In yesterday's session that included longer swims, the dongle was prone to speed artifacts during the swims, but all these had very high SDoP values, so they can easily be filtered out. May be a while until I get another chance for windsurf tests, the forecast looks bad. We probably jinxed it when we did not bring the light wind boards on our trip for the first time in 3 years...

Very interesting test. From what I have read patch antennas give the best antenna reception for your buck when flat mounted. Bigger the better, though even small ones are way better than watch antennas. The vk172 has a middling 18x18x2mm antenna. I had thought of putting one on the nose of my board with a 60mm ground plane for another 3 dB gain but that may be a bit of overkill given it will have a perfect Sky view when sailing. However I need to get another OTG phone first. Office Works wants almost 200 for a Moto E4 in Oz so that not an option.
Do you have trouble with having the VK172 holding the 5hz setting set on Windows with UCentre? Or have you written an Android program to change the default update rate?

Finally got a few windsurf sessions with the dongle, and the results were disappointing. In today's session, it had my top speed at 35 knots, about 3 knots too high. 2 second speed was about 1.5 knots too high. In a previous session, 2 sec was too high by 0.5 knots. SDoP values in the problem areas were around 1.5 - high enough to indicate problems, but below the default filter settings in GPSResults (and probably also ka72.com). This indicates poor reception, quite possibly because the dongle was lying on the phone, and the bag sometimes slipped on my arm.

Considering these results, the fact that phones with the required OTG support appear to be expensive outside the USA, and the fact that phones get ever-larger and barely fit into the bags anymore, I see no point in any further evaluation. A bluetooth dongle that would allow the dongle to be separated from the phone would possibly give better results, but no cheap u-blox (or Locosys) dongle is currently available. Wearing the phone on top of a helmet might also work well enough, but I rarely wear a helmet.

GPSLogit with the Moto E4 had performed very well in most of my tests up until today, with numbers typically being within 0.1 knots of the GW-60. But in today's results, the phone was high by 0.25 knots for 2 seconds, and low by 0.41 knots for the nautical mile. The tracks show multiple sections with multiple artifacts in the GPSLogit data (drops by 1-3 knots for 1-2 seconds). In one region, the phone is almost 4 knots lower than the GW-60 over 4 seconds, with the phone tracks showing obvious artifacts. I may post pictures and data on my blog in the next couple of days. These results illustrate that the phone GPS is not accurate enough for the competition, even though it can give very accurate results in some tests.

My reading indicated whist a patch antenna had better reception than a chip , the chip was not affected by oreintation so much. I guess that is what you found in practice.

probably more than you even wanted to now about GPS antenna here: avrproject.ru/EB-500/GPS_Antennas_ApplicationNote-GPS-X-08014-.pdf

Thanks for all the feedback after my last frustrated post. It made me realize that the issue was most likely from the bag slipping on my armband, which led to the GPS signal being partially obscured by my arm and body. I used a bit of velcro to keep the bag always facing upwards, and got much better results in my last two windsurfing sessions. GPSLogit can be quite accurate, and the USB dongle does again look like a viable option that provides accuracy estimates, as long as the phone stays facing upward. Details at boardsurfr.blogspot.com/2018/02/gps-dongle-test-results.html

Cheap Android phones with GPS-Logit can give some pretty good results. But we have got some shockers as well.
GPS-Logit with a ublox M8 BT dongle is extremely good, and I have seen no errors in the results, or indeed any variation from good GW** or GT31 results. (at 10Hz, dual GNSS)

My only complaint with the cheap phones is limited battery life, but it normally gets me through a typical sub 2hr session.

On battery life. My 3000 mAhr battery Chinese otg phone seemed to have less battery life than my old Alcatel pixi 3(4) with 1400mAhr which always had enough juice for my shortish sessions. Difference was the newer screen had twice the dpi (HD) and OS was Nougat 7.0 which seemed to use twice the resources of KitKat 4.2.2 especially after I took all the Google crap off the Alcatel.
Simpler the better for our needs.

I'd say most or all of them turn off GPS, but it usually can be turned back on separately, same as WiFi.

Useful tips, srtgumbee. Quite possible that different phone companies have different apps running by default, which would explain some variation in observed battery life. I had a 3-hour session yesterday, and the Moto E4 reported that the battery was still at 60% when I got home. The screen set to automatically adjust, which tends to be quite bright in the sun, but usually not 100%.

the battery shouldn't be a problem.
I tested several devices and usually it's no problem to record 8h and more.
with some devices 24h are possible.

I would not recommend cheap china phones. they might work sure, but chance that they don't is high. As example a user reported that his phones kills all apps as far as the screen gets off. The company though that this would be a good way to save battery live, but they forgot about that some apps like logging /music apps need to run in background.

sure the movement detection is possible, but not easy to do. Acceleration sensors works in 3 dimensions. Even everyone wears the phone on the shoulder, it doesn't say that it might move to the right or bottom etc.
also when you do waterstarts you hold your arm up, if display gets on, in worse case, a water drop can unlock the screen and stop your recording.

so using the hardware button to turn on the screen is usually a similar move as move the arm up,

and for easier control and feedback I already have an idea, that will work, It won't be finished the next months but hopefully for next Australia season .

So I'm interested, but if I can't find a cheap suitable phone, what's the chance of you bringing a couple over when you come.

Bringing a couple extras should be possible, but it won't happen until December.

That would theoretically leave time to fool around with a PiZero W + displays a phone alternative. Hardware cost for Pi + display + battery + cable would be around $50 in the US. Since that's not subsidized by phone companies, it should be comparable in Australia - could someone verify that? Highest cost would be for the display. The problem is that is would require a bit of assembly and geek knowledge to put together. Should be easier than making fins, though .