SKYRC GNSS Speed Meter anybody?

[SIMON CRAGG]

I have just purchased one of these for use at club fun fly events.

 

Registers max speed, avg speed, avg height, max height and distance etc.

 

On the face of it, a good bit of kit and the results of an event can be loaded onto the computer with a suitable map.

 

Has anybody any experience of these, any gotchas etc?

[Jake Bullit]

A mate just got one. Look a bit bulky and heavy.

If it were me, I'd probably get a speed flea.

 

https://speed-flea.com/

[EvilC57]

+1 for the Speed Flea.

[Phil Green]

Be aware that gps-based devices  are only accurate under saturated conditions, particularly at high speeds.
Experiments for our motorcycle racing club showed bikes cutting corners, often jumping across the midfield cutting half a lap, with software straightlining between insufficient datapoints giving wildly inaccurate results. I had plots, I'll see if I can find them.

 

[FlyinFlynn]

GPS track/speed/altitude logging is available from the RiD beacon designed and developed by fanfanlatulipe26.  It is capable of either recording a gps trace in CSV format for offline use or as a FlySky iBus telemetry stream. I haven't played with the telemetry so cannot comment on if the data is savable or not. It will of course suffer from the same problems that Phil commented on. 

 

Of course, it is easier, although more expensive, to just buy the commercial offerings!

 

 

[dave windymiller]

I have made one using Arduino, gps position/ speed with barometric altimeter which costs about 20 quid for the bits. Was thinking of detailing it on this site if anyones interested?

I use this in my Hotspot jet so size wasnt a key requirement but it could be shrunk with a proper pcb c/w processor chip. I have since removed the display and now vary the sampling rate up to 4 times a second depending on speed.  CSV data can be read into Google earth as seen below!

 

[Murat Kece 1]

Hi Dave That will be great to see/ learn and hopefully built it.

[GrumpyGnome]

Go for it! The electronics threads always seem to stimulate jnterest.....

[SIMON CRAGG]

After completing a few trial runs, the actual logger works a treat.

 

Average height, max height, average speed, top speed and distance all fine.

 

Compared to my cars speedo, more or less identical.

 

There is a downside though!

 

As far as I know, if the readings are recorded, the only way to clear them is via the software / computer.

 

I tried a few times to get the download to work, but it either froze / locked up the computer etc.

 

As I do not want to end up with frustrating hours trying to sort out my PC , I gave up. My system (windows 10) will not even let me completely remove it!.

 

However, all is not lost, as the logger can still be used perfectly well, but not in recording mode.

 

Not worth the aggro of trying to send it back to China etc.

[Barnstormer 52]

Hi Dave

If you have the time to do it I'm sure it would be of interest.

Put a bit of the E back in.

Geoff

[Barnstormer 52]

I did manage to create this last year when experimenting with the output from a Futaba SBS-01G using GPS visualizer.

The flight path is a bit erratic compared to John Lee's efforts from 2020 - Skywriting.

Needs work on the thickness of the trail etc.

It does show the flattening of the curves that Phil mentions.

Geoff

 

[FlyinFlynn]

So I took my RiD for a walk around my house....

 

 

I obtained the csv data

 

 

...showing lat/long, speed, altitude. Using https://www.gpsvisualizer.com/ I got 

 

 

(which actually isn't too accurate! but hey-ho.

 

So the device looks like this 

 

Weighs

 

 

is wired like this 

 

 

 

 

costs

 

 

and comes from https://github.com/fanfanlatulipe26/BaliseDGAC_GPS_Logger and looks like this on a PC/phone screen

 

 

Firmware available upon request.

 

All credit goes to https://github.com/fanfanlatulipe26/BaliseDGAC_GPS_Logger

[Keith Billinge]

I swear by my Speed Flea. Only 9g and it's great! Just plug into the balance lead on any lipo and wait for satellite lock.

KB

[Phil Green]

Surely these are only any use in a straight line?

For the bikes, once per second is way too slow, we found 10 samples per second too slow,

Even with 100% reception, which we achieved maybe half the time, at 100mph the curves were a series of 15' chords. 🙂
 

 

Edited March 21 by Phil Green

[EvilC57]

12 hours ago, Keith Billinge said:

I swear by my Speed Flea. Only 9g and it's great! Just plug into the balance lead on any lipo and wait for satellite lock.

KB

Have you found any problems caused by power up glitches KB?  I’ve had a Speed Flea 64 for several years now, and I’ve learned that I have to power the model up first, and then attach the the Speed Flea afterwards, and wait for it to initialise. Otherwise (I’m guessing) the electrical spike in the system caused by powering up the ESC afterwards can cause the Flea to malfunction. I have had flights were the unit has failed to register properly despite appearing to boot up correctly, and in each case it’s where I’ve forgotten to power the model up first.

 

Other than that and the display which is impossible to read in sunlight, it’s a great little device.

Edited March 22 by EvilC57

[dave windymiller]

Im interested in trying a ht1818z3g5l gps module so will order one for that price (next winters project!)!

 

Re the sampling rate, my view is im not after absolute accuracy of the flight speed at all times so banking turns im not to worried.  After a dive and horizontal high speed pass my jet clocked up to 235 mph on one pass (tailwind!).   I figure 0.25 seconds between points at high speed is good enough. I could push it to 0.1s but would need a faster processor.

 

I will post my stuff on the "electronics" area. I found it interesting digging under the gps bonnet!

[SIMON CRAGG]

I re-installed the SKYRC data logger software, and its now working perfectly.

 

Having had a speed flea, this SKYRC is a much better product IMHO.

 

Picks up satellites in about 20 seconds, as opposed to 5 minutes in some cases for the SF.

 

Easy to read.

 

Individual flights can be recorded and downloaded to the PC, showing a detailed map, track of model and a wealth of other info.

 

We are holding an Easter comp. where the gizmo will be used by all competitors........should be fun!. 

[FlyinFlynn]

12 hours ago, dave windymiller said:

Im interested in trying a ht1818z3g5l gps module so will order one for that price (next winters project!)!

 

It worked great straight off the bat for me but the firmware I used had a setting for the chipset that the module uses. The L80 is a MediaTek MT3339 and the HT1818z3g5 is a u-blox M8030-KT. They both output GGA  as delivered, but I'm not sure what else they might output which isn't needed for this application and will 'clog up' the data stream. The firmware I used set the baud rate and limit the sentences to PGA and RMC.  I don't know if your nano firmware does initialise the GPS module or not.

 

Cheap as chips huh! 

[John Minchell]

GPS satellite sensor generated data used to be used for speed telemetry in GPS Triangle glider racing.  That is not accurate enough in competitions, so now a pitot tube / head is used for more accuracy.  The GPS trace is used to plot the track on Google Maps.

 

Correct me if I am wrong, but FlyinFlynn - if you are at 230m to 240 metres above your house, are you not breaking the 400ft rule (122m) for drone with camera?

John M

[Dickw]

There is a problem with GPS if you have fast planes that also turn tightly as it seems that over a certain level of calculated G the GPS system assumes the latest position is an error and substitutes an interpolated position based on the last "good" track. Phil Green referred to this earlier. I did some experiments with GPS on my F5B planes back in 2016/17 and abandoned the idea as the results were useless.

 

F5B fly up and down a 150m course at high speeds with very tight turns at each end of probably around 10G+. The GPS system was rejecting the latest positions during the turns and substituting assumed positions based on the previous track on the straighter bits. After a few more readings confirmed it really was now heading in the opposite direction it jumped to catch up - by which time I was beginning the next turn 🙃.

 

The attached image shows the result. The yellow line in the middle represents the 150m course I was flying, and as you can see the GPS trace shows I appeared to be overshooting by about 300m in both directions. As a bonus the recorded max speeds were in excess of 300Kph 😀.

The GPS sensors in use were the SM GPS Logger or a home built one based in this article https://www.rc-thoughts.com/jeti-gps-sensor/

 

GPS works fine on my slower gliders for GPS Triangle racing where I use the RC Electronics system.

 

Dick

 

[FlyinFlynn]

On 23/03/2024 at 14:41, John Minchell said:

GPS satellite sensor generated data used to be used for speed telemetry in GPS Triangle glider racing.  That is not accurate enough in competitions, so now a pitot tube / head is used for more accuracy.  The GPS trace is used to plot the track on Google Maps.

 

Correct me if I am wrong, but FlyinFlynn - if you are at 230m to 240 metres above your house, are you not breaking the 400ft rule (122m) for drone with camera?

John M

I would be if I were flying! ....thats my house that is 240Metres AMSL 🙂

[Keith Billinge]

On 22/03/2024 at 08:24, EvilC57 said:

Have you found any problems caused by power up glitches KB?  I’ve had a Speed Flea 64 for several years now, and I’ve learned that I have to power the model up first, and then attach the the Speed Flea afterwards, and wait for it to initialise. Otherwise (I’m guessing) the electrical spike in the system caused by powering up the ESC afterwards can cause the Flea to malfunction. I have had flights were the unit has failed to register properly despite appearing to boot up correctly, and in each case it’s where I’ve forgotten to power the model up first.

 

Other than that and the display which is impossible to read in sunlight, it’s a great little device.

I generally attach the speed flea to the battery balance lead after it's plugged into the plane. So I havenet noticed the problem you describe. Also the person that's worried about 1 second updates. That just the screen the thing runs ant some crazy Mhz speed to actually do the speed calculations, but only updates the scree every 1 sec. You pull the barttery and the speedflea out of the model upon landing and it gives you the max speed and the max altitude etc...
The clubmate with the best eyes has to read it though. Because it's a bit crap in direct sunshine.

[EvilC57]

Four times a second according to the Speed Flea website.

[EvilC57]

After giving a +1 for the Speed Flea earlier in this thread, mine seems to have packed up and died completely 😩.

 

Looking around for a possible replacement I’ve come to the conclusion that all possible contenders are somewhat larger than the expired SF, and therefore too big to fit in a small fuselage. I am however attracted to the SkyRC GSM020 Performance Analyser, which works via an app on your phone. Does anyone have any experience with this device?