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Spent a pleasant few hours this morning testing 18hz gps units. Manfred's latest creation works great with GPSLogit via bluetooth. Very little between the 2 18hz units as they both use U-Blox 8 chipsets. Both in the same bag and protected with condoms...minus the lubricant!

Here's some of the 10 sec data.


<div>10 sec
GPSLogit BT 18hz U-blox18hz
10:25:31 175.8m 34.172kts +/- 0.127 10:25:32 175.9m 34.155kts +/- 0.116
10:41:29 171.2m 33.246kts +/- 0.135 10:41:29 173.9m 33.771kts +/- 0.118
09:54:50 172.8m 33.562kts +/- 0.124 09:54:46 170.9m 33.192kts +/- 0.120
09:39:31 170.5m 33.115kts +/- 0.116 09:39:31 169.7m 32.956kts +/- 0.119
09:43:46 170.4m 33.090kts +/- 0.124 09:43:46 171.4m 33.377kts +/- 0.133
5 x 10 33.431 5 x 10 33.470

File size is pretty big at 18mb so it wont load on GPSSS or KA72 until they tweak their systems.

Do my eyes deceive me or are the differences between the two units greater than the reported accuracies???? I guess you have to add the two accuracy figures together, so in the case of 09:54:50 +/- 0.244 with a difference between the two results of 0.37

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Roo said..
Spent a pleasant few hours this morning testing 18hz gps units. Manfred's latest creation works great with GPSLogit via bluetooth. Very little between the 2 18hz units as they both use U-Blox 8 chipsets. Both in the same bag and protected with condoms...minus the lubricant!

Here's some of the 10 sec data.


<div>10 sec
GPSLogit BT 18hz U-blox18hz
10:25:31 175.8m 34.172kts +/- 0.127 10:25:32 175.9m 34.155kts +/- 0.116
10:41:29 171.2m 33.246kts +/- 0.135 10:41:29 173.9m 33.771kts +/- 0.118
09:54:50 172.8m 33.562kts +/- 0.124 09:54:46 170.9m 33.192kts +/- 0.120
09:39:31 170.5m 33.115kts +/- 0.116 09:39:31 169.7m 32.956kts +/- 0.119
09:43:46 170.4m 33.090kts +/- 0.124 09:43:46 171.4m 33.377kts +/- 0.133
5 x 10 33.431 5 x 10 33.470

File size is pretty big at 18mb so it wont load on GPSSS or KA72 until they tweak their systems.

Thanks for sharing. These numbers cause concern - the ranges for 3 of the 5 runs do not overlap. For the second run, the averages differ by about 8 standard deviations, which indicates that the statistics are invalid, and the +- numbers are way to optimistic.

The third run shows a 4 second shift between the two GPS units, which is another cause of concern. However, that could be due to missing data points, and how GPSResults currently handles that. Easy to check if you look at the data points around 09:54:56 on the second unit.

The second unit is probably my unit, it won't miss any datapoints, but it could have datapoint CRC errors...

I've been testing with a device on bluetooth and found some strange things with data lag.
Data comes in 4 to 20ms after it was send.
If antenna placement is not optimal it will negotiate new speed, this negotiate takes between 20 and 40ms.
During times with high lag and speed negotiations I've seen drops in datapoints.

Due to the fact I'm still tweaking the standard software I skipped Bluetooth troubleshooting for the moment.

Does the unit have to be bluetooth? can it not just be plugged in with micro usb.

also

does the unit have to run at 18hz would lowering the frequency improve accuracy or overloading the system with data?

please type response slowly so I have a farting chance of understanding

The easiest way to build and test prototypes is with BT, to transmit the data to GPS-Logit for saving to the micro SD card. It also has the advantage of the screen for all the usual GPS-Logit data display and confirmation that logging is actually taking place with the correct data sentences. This is actually what I personally think is the best solution anyhow. Adding an SD card to the receiver would complicate it a bit more but I guess it could be done.

The 18Hz data I am getting from Manfreds BT receiver (to GPS-Logit) has no missing data at all and shows very good (low) error values. I am wearing the receiver in my helmet though, (skiing) and getting 9+ satellites a lot of the time. The error values seem significantly higher with only 6 satellites using 18HZ, but more data and testing is needed to get a better picture of this.

The Ublox M8 series of GPS chips can log @ 18Hz using the GPS system only. If you cut it back to 10Hz it can use multiple GNSS systems, Eg: Gps and Glonass. This make a lot more satellites visible and usable and in theory may improve accuracy and consistency as a result. I am trying to test this at the moment but so far my 10Hz files seem to be GPS only.

BTW. My typing is always very slow........

I need slower

re the Bluetooth I wasn't referring to the unit having an internal logger to card but instead of Bluetooth be hard wired via USB, thinking the data transfer would be more efficient being hard wired.

Plus I wonder how many functions you can have running simultaneously with Bluetooth as I find Talky a huge benefit

The trouble with hard wiring, is that the receiver is going to be on your arm instead of your head.
And there's probably not going to be room for it in our preferred pouch.
You could always use non blue tooth earphones.

Not a problem Elmo, I run BT GPS, BT headphones and BT heart rate monitor all at once.

Good signal reception yesterday 9 to 10 sats at 18hz for a few hours of windsurfing. I find it best to have the antenna highest on the arm pointing to the sky, when I had it under the phone it received fewer sats.

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Roo said..
Not a problem Elmo, I run BT GPS, BT headphones and BT heart rate monitor all at once.

Good signal reception yesterday 9 to 10 sats at 18hz for a few hours of windsurfing. I find it best to have the antenna highest on the arm pointing to the sky, when I had it under the phone it received fewer sats.

Colour me red and ruffle my fur, showing my humungous knowledge of electronicals, I thought you could only run one bluetooth at a time.

Thanks for the 2 words a minute guys

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Roo said..
I run BT GPS, BT headphones and BT heart rate monitor all at once.

Receipe for fried Roo ?

Likelihood of me having any more kids is now zero...I glow in the dark when everything is switched on!

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elmo said..
I need slower

re the Bluetooth I wasn't referring to the unit having an internal logger to card but instead of Bluetooth be hard wired via USB, thinking the data transfer would be more efficient being hard wired.

Just to make it clear, or as clear as possible :

Bluetooth is a wireless technology. Kind of short range wifi.

The GPS module output is hard wired to the Bluetooth Transmitter module and the Data is sent wirelessly to GPS-Logit running in an Android smartphone (miniature computer) where all the good stuff is done. (recording to SD card, comprehensive all division results display, speed talk etc)