GPS for acceleration timing.

[decrep]

I notice a lot of people, mainly X Power owners checking their acceleration times using a stopwatch.
At the Xpower times, I think user reaction times probably play a significant part.

I'm wondering if anybody would be interested in our speed windsurfing technology.

Off the shelf GPSs can be quite expensive if you want accuracy.

A few of our members, have been experimenting with DIY models, that can be built for a fraction of the price.
I plan to do a test with our SE SR, and see how close it gets to the claimed 7.7s 0-100kmh.

I'll post a pic of the results.
Let me know if you're interested?

There's only 3 components to the simplest logger without display and you only need delicate soldering skills to put the electronics together.

There's some configuration of the GPS that needs to be done, no problem if you have basic computer skills.
The case can be anything. You don't need it water proof, like us.
The version with display is a bit more expensive, and is useful for checking the speedo.

Here's my PB acceleration, from 2022. 0 to 40Kts in 27.8s, just to show what I mean. But this is an older GPS that records at 5hz, so it's only resolving 0.2s, the new ones run at 10hz so good for 0.1 sec

28s is too long for this window to show the whole time figures, but you can see the start at 08:03:00.8. Off the page, the finish is at 08:03:28.6.
So if anybody doubts your claims, you have the proof here.

I'll get around to doing the MG4 in a few days, when we get on a 100kmh road.

 

[mg4mc]

I'd be interested in more details. I used to have a Draggy, but it was in my Golf R when it was stolen ?

 

[decrep]

I'd be interested in more details. I used to have a Draggy, but it was in my Golf R when it was stolen ?

Well there's lots of details, not sure where to start.
I have no idea what a Draggy is, so that doesn't give me a reference.
Are you interested in building one?
Do you want a simple logger or a more complex display?

 

[siteguru]

Dragy DRG70C + Free Dragy Window Mount!

Monitor your 0-60mph, 60-130mph, 100-200kmh, 1/4 mile, 1/2 mile performance, and more! Dragy uses high speed GPS satellites to accurately measure your vehicles performance within 1/100th of a second, producing identical results to the much more expensive VBOX system, in a less expensive and...

dragymotorsports.co.uk

 

[RobR]

Following...

 

[decrep]

Dragy DRG70C + Free Dragy Window Mount!

Monitor your 0-60mph, 60-130mph, 100-200kmh, 1/4 mile, 1/2 mile performance, and more! Dragy uses high speed GPS satellites to accurately measure your vehicles performance within 1/100th of a second, producing identical results to the much more expensive VBOX system, in a less expensive and...

dragymotorsports.co.uk

Well that's more accurate, as you'd expect from a dedicated racing device. it resolves 0.01s, ten times the accuracy of my 0.1s. Depends if you want it down to 100ths of a second or can make do with 10ths

That sounds quite reasonable at AU$280 That's cheaper than a windsurfing GPS or an accurate GPS capable smart watch at only 10hz

But you can make one a lot cheaper.

The recommended GPS unit for windsurfing is a Beitian either an M8 or M10 firmware, Depending one the sky view from the car, (Best at the front of the windscreen), is what size antenna you need.
Some models come with a compass, we don't need that.
The biggest is a BN880

But looking at this chart the M10 only does 4HZ, but the M9 does 25hz, may be better for those short times, but I have no experience configuring an M9.
May need some other input here, if you want togo that way.
Easiest way is to use a spark fun open log, to load the raw data on to an SD card.
And a lipo battery of around 1000mAh to power it.

Here's a write up by the developer of the display unit, RP Conrad

Minimal solderskills are needed, as just the GPS has to be soldered to the right pins. Total budget is around 40?. Some technical details :
ESP32 board with e-paper display (Lilygo TTGO T5, 15$)
Beitian BN220 / BN280 gps (ublox M8n engine), 10$
Lipo 2000 mAh, with protection, 10$
Sealed case, 5$
A log rate of 10 Hz is possible, format UBX NAVPVT.

So any questions? I'll do my best to answer them.

The display firmware is open source and contributed to by a few people.
It's on github here

GitHub - RP6conrad/ESP-GPS-Logger: GPS logger for Speedsurfing, based on ESP32 & Ublox M8N hardware.

GPS logger for Speedsurfing, based on ESP32 & Ublox M8N hardware. - RP6conrad/ESP-GPS-Logger

github.com

Along with building and set up instructions.

The analyzing software, costs beer money and is here.

GitHub - prichterich/GPS-Speedreader: Software for analyzing GPS tracks - speedsurfing, winging, and windfoiling

Software for analyzing GPS tracks - speedsurfing, winging, and windfoiling - prichterich/GPS-Speedreader

github.com

But this is dedicated speed windsurfing stuff, designed for our GPSTeam Challenge.

As the firmware is open source, anybody smart enough should be able to modify it for their own needs.
As it is to get 0 - 60 standing 1/4 mile etc would have to be done manually, from time, speed and distance data.

The data is derived from doppler calculations, not positional calculations, which is much more accurate.

Here is a link to where the display all started. It star5ted 3 years ago, and has grown like topsy ever since, so there a lot to wade through, but there is info in there if you're interested.

Another DIY GPS logger approach | Windsurfing Forums, page 1

Another Diy Gps Logger Approach and other windsurfing discussion in the Seabreeze gps and speed talk forums, page 1

www.seabreeze.com.au

And here is the start of my experimenting with simple loggers. Started 6 years ago and a lot has changed since.
Different GPS modules, different battery and charger

DIY GPS Logger | Windsurfing Forums, page 1 - Seabreeze

Diy Gps Logger and other windsurfing discussion in the Seabreeze gps and speed talk forums, page 1

www.seabreeze.com.au

I've been re configuring my logger, so here are the parts.

This the 3.7v LiPo battery with DFR0668 LiPo Charger, a simple on off switch, the open log data recorder and the Beitien 280 GPS module. I'm not sure how well this will work on 3.7 volts, the range is 3.6 to 5.5 the optimum is 5v. I'll just have to keep it charged up I guess.

The previous iteration used a "buck boost" model to give 5v VCC, but it was playing up, so I'm trying something simpler.

Here's the circuit of the logger

I got it all together today, after some of the short circuits I'd accidentally incorporated. Tested the battery protection thoroughly. My soldering skills aren't what they were.

Results look good so it's working fine without having to worry about boosting Vcc to 5v

So I have some results, and happy to say the SE SR is right on claimed, well when going downhill a bit.
I did 3 runs, first fairly flat, 2nd slightly up hill 3rd slightly down hill.
Each run it took 0.4 sec to get from 60mph to 100km/h
Temp 21C battery 80%
1st run

In knots of course, and I using 60mph = 52.14 knots and choosing the closest number to that.
In this instance it's 52.317 so a tad faster, but close enough. Start time was 39.5 60mph is 47.1 giving 7.6s. Distance at start was 327.7 at 60mph it's 438.8 so 111.1m

Interesting the acceleration curve, it's fairly straight up to 40mph, then starts tapering off.

My other 2 tests were fairly similar, giving the 0 to 60 at 8.2 for the uphill one and 7.5 for the slightly downhill test.

 

[mg4mc]

Can you get the gradient from your data? The Dragy only declared results valid if the slope was < 1% - I found it really hard to find a (quiet) road that complied, even on the "flat" Cheshire plain where I live.

 

[decrep]

Can you get the gradient from your data? The Dragy only declared results valid if the slope was < 1% - I found it really hard to find a (quiet) road that complied, even on the "flat" Cheshire plain where I live.

I can get the tracks on Google Earth, to show where the 0-60 was, but how you'd get road gradient from that I don't know. I guess the Govt road people would know, or a proper survey map may show it.

This was the first run, and probably the flattest. But if I'd felt like driving another 10kms or so, the road gets much flatter.
I can probably get vertical height in the data, but it's reputed to not be very accurate

 

[DixieTGS]

GPS absolute height data is much less accurate than horizontal, but over such a short time the relative height difference may be accurate enough if the satellites used don't change ?

I know nothing about the doppler measurements you get - are they the ones you are referring to as not being very accurate in the vertical direction?

For locating potential sites in the UK, you can use Ordnance Survey leisure maps (free on the Bing maps website). Spot heights are shown here and there as a black dot on the road, with a height in metres by it also in black.

 

[decrep]

The analytic software I'm using, doesn't process altitude, and it's possible the NAVPVT sentence I'm saving also doesn't have altitude. I'll have a look at some files with the UBLOX software, and see what's going on.

So doppler data, doesn't give absolute position. it's only looking at changes, but it's much more accurate than absolute positional data, it doesn't work on a grid system.
Years ago when using proprietary units that were for general use, I've seen obviously false altitude results, but having never been interested in altitude I've no idea why.

I've had a look at the NAV-PVT sentence, and it does contain this info.

uint8 numSV # Number of SVs used in Nav Solution
int32 lon # Longitude [deg / 1e-7]
int32 lat # Latitude [deg / 1e-7]
int32 height # Height above Ellipsoid [mm]
int32 hMSL # Height above mean sea level [mm]
uint32 hAcc # Horizontal Accuracy Estimate [mm]
uint32 vAcc # Vertical Accuracy Estimate [mm]

So I'll have to boot into my windows laptop, load U-Center and see what these files look like.

Maybe back this arvo with the details.

A bit of a struggle, my old laptop only has windows 7 on it and the latest U-Center doesn't want to work on it.
So I found an even older laptop, already with U-Center on it.
You guessed it, it's a long time since I played with U-Center.

But I think it's what you need, (well I know you'll need it to set up the UBlox chip)

u-center

GNSS evaluation software for Windows

www.u-blox.com

I got an altitude graph, with speedo and altitude meter. But I couldn't figure out how to get a speed graph, I'm sure it's in there somewhere, you just have to find it.

I also couldn't see the altitude accuracy data. But the absolute is obviously wrong, it's got me driving along below sea level! That doesn't matter as long as the relative elevation is correct.

That ancient laptop is very slow and frustrating, so I didn't take too long playing with it. Hopefully if you have a recent windows edition, it will run the latest U-Center and be easier to use.

Can't resist a challenge, installed the version from the ancient laptop, to the merely old laptop and it works much better.

So here is the speed view of all 3 runs. It's a bit hard to see now I've posted it. But there's a little button just above the Firefox icon, that says "Speed"
Under that is all the available views, a whole pile of them, including altitude accuracy.

So yes I'm fairly sure you can get all the info you need.

 

[decrep]

Had a thought that you might like to try my .UBX file in U-Center and/or GPSSpeadreader. to see if you can get the results you want before building a unit.

So I've attached, my car run file, it says UBX isn't an allowed extension, probably an anti malware precaution. I'll try adding .pdf at the end, which you'll have to remove once you've downloaded it.
That seems to have worked, just don't be surprised if you PDF reader says it's a corrupted file, or your anti virus software doesn't like it. Get back to me with any problems

 

[decrep]

Saying all that I now don't see how to download it.
Perhaps give me your email address and I'll send it that way.

 

[DixieTGS]

Ok, that all went well. The rename to pdf did the trick, U-Center installed with no trouble on Win10, the file read in and gives a sensible plot when I bring up a chart with a y property of speed and press play.

As per your suggestion I'll have a decent look at it all before deciding whether to build one. The hardware assembly looks like the easy bit for me despite it not being my background, it's understanding how to use all the software and development tools that I'll struggle with.

Now all I've got to do is find the time .

Thanks for all the info.

 

[decrep]

Great Dixie.
Yes, the programing can be fiddly.
For the simple logger, you need a serial to USB connector, so the computer can see the UBLOX output.

Whereas the display unit programs the GPS chip. You just need to load Jan's firmware onto it. For that you need an arduino thingy, (sorry forget it's name, but it will be in Jan's instructions I posted earlier)

As it doesn't need to be waterproof, you can disregard, the rocker switches and magnets for turning it on, and the inductive charging pad.

I look forward to your progress, when you find the time.

 

[decrep]

I've just noticed Jan has completed another project.

GitHub - RP6conrad/T_display: ESP-GPS with T-display

ESP-GPS with T-display. Contribute to RP6conrad/T_display development by creating an account on GitHub.

github.com

An LCD display instead of the epaper display.

It looks similar to set up as the epaper.

The main advantage for the displays, over the simple logger apart from the display, (which is probably of little benefit to automotive users). It has wifi downloads, instead of having to plug an SD card in and out.

The epaper maintains the last page after shutdown. The LCD doesn't.

Jan is based in Belgium so his suppliers may be more relevant than mine. He is also extremely helpful.

 

[vincpa]

I notice a lot of people, mainly X Power owners checking their acceleration times using a stopwatch.
At the Xpower times, I think user reaction times probably play a significant part.

I'm wondering if anybody would be interested in our speed windsurfing technology.

Off the shelf GPSs can be quite expensive if you want accuracy.

A few of our members, have been experimenting with DIY models, that can be built for a fraction of the price.
I plan to do a test with our SE SR, and see how close it gets to the claimed 7.7s 0-100kmh.

I'll post a pic of the results.
Let me know if you're interested?

There's only 3 components to the simplest logger without display and you only need delicate soldering skills to put the electronics together.

There's some configuration of the GPS that needs to be done, no problem if you have basic computer skills.
The case can be anything. You don't need it water proof, like us.
The version with display is a bit more expensive, and is useful for checking the speedo.

Here's my PB acceleration, from 2022. 0 to 40Kts in 27.8s, just to show what I mean. But this is an older GPS that records at 5hz, so it's only resolving 0.2s, the new ones run at 10hz so good for 0.1 sec

28s is too long for this window to show the whole time figures, but you can see the start at 08:03:00.8. Off the page, the finish is at 08:03:28.6.
So if anybody doubts your claims, you have the proof here.

View attachment 28770

I'll get around to doing the MG4 in a few days, when we get on a 100kmh road.

Hey decrep,

I've got draggy but I can't figure out the format of the GPS coordinate system. Looks like this

-2028.256500 -9052.102980

Do you have any information on how I can use this? Cheers

 

[decrep]

Sorry mate, those numbers mean nothing to me. I don't understand the - sign for a start.

I also know nothing about the draggy, what format does the GPS data come in?

Edit I've just checked it's website, and it says nothing about exporting data. Where did you get those numbers from?

 

[vincpa]

There's an option to export the data as a VBO file, here's a sample. I've tried many different positioning systems but I've come up with nothing. I'm going to try and contact support but I don't expect a quick or even meaningful response. The actual race data was captured at -33.8036869078748, 150.8691550043412 so these numbers are not even close.

File created on 05/09/2024 @ 09:43

[header]
satellites
time
latitude
longitude
velocity kmh
heading
height

[channel units]

[comments]
Generated by dragy Lap
Model: dragy DRG70
UTC Date Started: 05/09/2024 09:43

[column names]
sats time lat long velocity heading height

[data]
031 094303.500 -2028.260700 -9052.110660 000.094 129.50 +00061.10
031 094303.600 -2028.260700 -9052.110660 000.043 129.50 +00061.10
031 094303.700 -2028.260700 -9052.110660 000.061 129.50 +00061.10
031 094303.800 -2028.260700 -9052.110660 000.050 129.50 +00061.10

 

[DixieTGS]

If you divide the values by 60 you get
-33.804345
-150.868511

Your location shows as Sydney which google reckons is
33.8688° S, 151.2093° E

The negative latitude for south seems right but I thought negative longitude would be west ?.

Aha, would you be at drift school Australia by any chance?

The divide by 60 suggests the lat lon are in decimal minutes, not any of the more common formats, e.g. decimal degrees.

 

[vincpa]

Thank you Dixie, that seemed to work out the values. Although there's still something off about them I need to pull some hair out over.

Not drift school Australia, it's Eastern Creek in NSW. Got a friend to do a test drive to see if we can work out the GPS format. Divide by 60 is on the right track!