Vbox sport new versions reduced to 10Hz

Discussion related to external and internal GPS / GLONASS / Galileo / BeiDou sensors
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oldnick
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Vbox sport new versions reduced to 10Hz

Post by oldnick » Fri Jun 28, 2019 4:57 pm

For vintage car racing we've used Vbox sport with Harry's Laptimer very satisfactorily (esp. for sector training), and were considering fitting more cars, so looked up the new versions ... and found out they sampled gps twice slower than before (10 Hz vs. 20Hz) !

this is reflected on the spec sheets (in essence identical but half the gps rate); it still shows on some webpage:
https://racelogic.support/02VBOX_Motors ... cification

I exchanged with the company to get some explanation, and got as a reply that pcb redesign for unifying products (they also offer a standalone touchscreen version now - also 10Hz) led to include glonass and reduce gps rate, purportedly offering better results in spite of half the sampling rate...

I'd like to know what is sale pitch and what is hard scientifically measurable evidence of these enhanced performances at 10Hz before purchasing external gps units:
has anyone compared actual performances of the older 20Hz Vbox sport to the new 10Hz Vbox sport, esp. for a track use?

Harry : do their explanation make sense to you (glonass advantage for accuracy and not only coldstart time)? do you manage to interface the native gps signal from the vbox before some averaging/filtering that they may do prior to logging - and do you confirm the new 10Hz version is indeed an improvement over the 20Hz version for track use ?

my gut feeling is that all else being equal, as long as one gets a clean signal, higher gps sampling frequency makes for better track logging... and we may need to get other 20Hz or faster external gps to keep the performance level up to our current standard (any recommendation?).

thank you !

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Re: Vbox sport new versions reduced to 10Hz

Post by Harry » Fri Jun 28, 2019 6:48 pm

I have no access or experience with the new version. So just some thoughts:
  • The old version used a GPS-only chip capable to handle 20 Hz. As they support GPS+GLONASS now, they have changed the chip set completely. It is well possible this chip set is designed for 10 Hz, making the 20 Hz not a dropped option but a hard hardware limit.
  • Adding GLONASS support allows GNSS chips to use up to two times the number of satellites. Every satellite added can improve position accuracy and reduce the drop out risk (loss of position lock). All GNSS accessories come with multiple systems support today. Besides GPS and GLONASS, BeiDou and Galileo are important now. It has been time or even mandatory to upgrade for RL.
  • While 20 Hz sounds (and is) better, 10 Hz is usually fine for data analysis. Timing accuracy in LapTimer is depending on accuracy mostly , not update rate. So it is well possible GLONASS-added accuracy is adding more precision than the lost rate reduces.
  • The main question is whether the VBOX's optimization for race track scenarios is a big enough advantage to justify the high price (comparing it to 10 Hz solution not optimized for track use). My expectation for an hardware update would have been to get both GLONASS *and* 20 Hz...
  • In any case, an external antenna should be used for the VBOX. The antenna plug is one of the main advantages it has compared to other solutions from my point of view.
As you can see, I cannot really make a recommendation without having insights Racelogic has, or a test could reveal. But maybe the above thoughts help a bit.

- Harry
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Re: Vbox sport new versions reduced to 10Hz

Post by oldnick » Fri Jun 28, 2019 7:46 pm

Hi Harry,

thank you for your prompt reply. So far I get a fishy impression from the answers given by Racelogic...

- from what I've read (admittedly not a whole lot yet), on Garmin and similar outdoor oriented devices, glonasss compatibility is mostly (only imho) helping cold startup time : yes, there are more satellites, but apparently one needs to work with one set or the other, so in a canyon type environment you increase the odds of getting several satellites of a set, then this set is picked up and the gps only works with it (same resolution or just about between the two sets - unless you are near the poles where Glonass has better coverage). The glonass compatible recent handheld devices benchmarks I've seen only show improvement in cold start time, not in accuracy.
- Racelogic may well have considered they had to include the Glonass compatibility for marketing reasons (not stay behind competition on compatibility ground, etc.), which may have resulted in a performance limitation for their devices (your first thought) - yet nothing they indicate actually supports their claim of improved accuracy (not their datasheet, nor benchmarks from their teams) : Glonass added accuracy sounds like a sales pitch to me, until proven otherwise (I've specifically asked them for technical evidence... still waiting: I'll report back here if I get anything).
- on a race track one usually have no issue with satellite locking (places are very opened, no mountains around, signal is good) - so for our purpose Glonass compatibility of cold start improvement is irrelevant.
- there is a chance they are just manipulating the performances until their suppliers have got rid of their current stock from an older generation, would not be the first time a consumer electronics company does that, considering most customers are one shot deals...

I understand signal quality is important (and we have external antennas on our steel bodied cars using vbox sport previously - it's unclear if the composite bodied cars we'd like to install may benefit from them, not knowing if the internal antenna is as efficient as an external antenna , like e.g. in the open on a motorcycle). Obviously high sampling rate garbage is not a good thing to work with... but I have the feeling loosing half the sampling rate would be detrimental to track users who should get good signal quality... Considering the price of the unit that seems a game changer for us, unfortunately.

A real life, independant back to back test would sure be of interest... though short of that I feel inclined either to source older units while there are some on the market, or rather turn to an other manufacturer altogether, as when trust is gone one can't rely on a manufacturer anymore and hanging on too long becomes a source of frustrations sooner rather than later...
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Re: Vbox sport new versions reduced to 10Hz

Post by Harry » Fri Jun 28, 2019 9:11 pm

To my knowledge, modern GNSS chips combine information from multiple satellite systems. It is not one or the other. This would hardly make sense and not increase accuracy. This will change once Galileo is fully implemented - it is providing higher accuracy than GPS or GLONASS.

The technical spec of GNSS chips does not tell you too much. Accuracies shown are all the same and show the values achievable with the GPS type technology. In reality, results will always be worse. The question about the share of measurements being near the spec. It is 90% or just 20%.

Losing the lock is a relevant issue on any track in a none-flat environment, and in case you have trees around.

Cold startup times are irrelevant nowadays. In the early GPS times it could take several minutes to get the first lock, but that's over.

Another characteristic of GNSS chips is what I named "optimization for race track scenarios" above. You may have seen that consumer level GNSS solutions like the chips built into smartphones, deliver extremely smoothed speed values and will often "overshoot" when cornering. This is due to the fact that measurements are noisy / low quality and heavy smoothing needs to be applied to get something reasonable for the user. On tracks, such data is fine to measure lap times, but not to get a detailed analysis of line driven / break points etc. The (old) VBOX Sport always delivered by far better data here.

On antenna again: internal antennas are always a compromise. For my tests on Nordschleife, a VBOX Sport delivered worse data compared to the old XGPS150 when using the internal antenna. When using an external one, it showed *by far* more precise results than the Dual.

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Re: Vbox sport new versions reduced to 10Hz

Post by aMacUzr » Mon Jul 01, 2019 7:04 pm

I run on a local short track that has many large trees lining about 1/2 of the track and some of the spots on the track are problematic for GPS/GLONASS lock.

I have run with each of the following:

- front and back Vicovation Opia2 dashcams (1 Hz, GPS-only AFAIK) with external GPS "mouse" attached to front and back windshields

- Dual XGPS-160 (10 Hz, GPS/GLONASS) mounted in center of rear-window deck

- VBOX Sport (20 Hz, GPS) with external antenna mounted in the center of the rear trunk deck

The dashcams both lose GPS lock regularly on the track, even though (strangely) they get good GPS lock while parked in my garage which is a GPS-dead zone for most other devices.

The XGPS-160 usually keeps lock but, judging from the plot of the track using the LapTimer data exported for Circuit Tools, is not as accurate as the VBOX Sport's data.

The VOX Sport hasn't lost lock yet (used for 2 track days, thus far) and appears to capture the most accurate data/"track."

My main reason for purchasing the VBOX Sport (already had the XGPS-160) was that (when set to do so) it is supposed to "always" record to its memory card, whether or not it's sending data via Bluetooth (e.g., to LapTimer). That way, if/when there was a glitch with data-capture via LapTimer, I would always be able to build videos anyway (I use RaceRender 3 to combine various cameras and data streams). In reality, the "will always capture to memory card" has had its own glitches. If VBOX Sport had been the 10 Hz version when I purchased mine, I would have been much less likely to purchase it, given the price.

BTW, when I tried to run the XGPS-160 in its "record the data" mode, it reverted to 1 Hz GPS-capture rate (both in its memory and what it sent to LapTimer). Don't know whether that was a bug with a specific version of firmware because I gave up on the XGPS-160 at that point.

HARRY: It would actually be nice to be able to tell LapTimer to "use this GPS device" when there is more than one available.
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Re: Vbox sport new versions reduced to 10Hz

Post by Harry » Mon Jul 01, 2019 7:13 pm

Thanks for your insights!

In case you have both the XGPS and the VBOX active, there is only one option to force the use of one device: unpair the other device in your smartphone's BT settings - this will make it invisible for LapTimer

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Re: Vbox sport new versions reduced to 10Hz

Post by aMacUzr » Mon Jul 01, 2019 7:24 pm

Harry wrote:
Mon Jul 01, 2019 7:13 pm
In case you have both the XGPS and the VBOX active, there is only one option to force the use of one device: unpair the other device in your smartphone's BT settings - this will make it invisible for LapTimer
As the kids would say "Du-Oh" ... so obvious (he says, somewhat red-faced). Thanks, Harry.
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Re: Vbox sport new versions reduced to 10Hz

Post by oldnick » Wed Jul 10, 2019 6:14 pm

aMacUzr wrote:
Mon Jul 01, 2019 7:04 pm
If VBOX Sport had been the 10 Hz version when I purchased mine, I would have been much less likely to purchase it, given the price.
me too, and I still don't understand how they will convince customers just by stating "it now works better at 10Hz than it was before at 20Hz"...

I guess some benchmarking would be the convincing approach to show how "better" the datapoints are sampled on a given track, should not be that difficult for them to mount 2 on a car and do a couple laps...

So as a result we've downshifted our metrology investment plan to neutral, awaiting for a clearer picture. I'm not even sure of the interest of purchasing some "old" 20Hz Vboxes now, though we were quite happy with them so far.

ps: my interrogation regarding external antenna performance vs. without was for use in fiberglass cars, so I guess a relevant comparison would be with motorbikes or other open air mounting (we do use a roof mounted external antenna on the metal bodied cars)
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Re: Vbox sport new versions reduced to 10Hz

Post by aMacUzr » Sun Jul 14, 2019 5:35 pm

ps: my interrogation regarding external antenna performance vs. without was for use in fiberglass cars ...
Somewhere on either the US or British RaceLogic sites there's a statement about adding a minimum-dimension ground-plane if using an external antenna on a non-metal car. This can be constructed out of something as simple as aluminum foil and could either be added to the outside (e.g., using good 2-day tape) or permanently to the underside of the fiberglass (if on the outside, the cut-out around the antenna should be tight/accurate). If adding to the underside of the bodywork, I'd likely go for a thin-guage aluminum and attach it using contact cement. In general, the larger the ground-plane, the better, but it should be relatively flat.
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