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I know that a Vbox Sport gets velocity information from GPS but where do the more expensive Vbox units get speed from? CAN?
I'm wondering because I was playing with the Vbox Sport today, connected to Porsche's Track Precision app. I exported the data from Track Precision as a Vbox vbo file, copied the .vbo file from the Vbox Sport and compared the two in Circuit Tools. In the screen captures below, the blue line is from the Vbox and the red line is from Track Precision. There are some big spikes in the Vbox data and it's wrong: I wasn't really going 110 mph in my neighborhood! I mapped the spikes and they are from places on my route where there's heavy tree cover; so probably, the Vbox Sport lost coverage for a moment and it resulted in bad data.
Vbox Sport data
Track Precision data
The spike really isn't an issue, as none of the tracks I'm likely to drive at have any tree cover. However, it did make me curious about where a more expensive Vbox gets velocity data from.
The second interesting thing I noticed was the difference in the two .vbo files. I probably should have realized this but the Porsche one includes all the data that comes from the car's ECU, via the Sport Chrono package and its WiFi connection. There's lots of data, each field listed under "[header]". My favorite is "charisma damper"! I don't know if these are standard .vbo data fields but Circuit Tools does show them when you open the Track Precision vbo file; cool.
.vbo comparison: Vbox Sport on the left; Track Precision on the right
Lastly, I noticed that if I overlay the two .vbo files in Circuit Tool they get out of sync over time. If you look at the screen capture above, you'll see that I edited both vbo files so that they start at exactly the same time. (Look at the bottom, under [data]. The second value is time: UTC time on the left in the Vbox file; PDT on the right in Track Precision.) They don't finish at the same time because the Vbox records until the car stops, while Track Precision stopped when I drove across the finish line...but that shouldn't matter; they still should be in sync. Any ideas? Perhaps Circuit Tools uses elapsed time and not absolute satellite time, so if there's missing data, there will be a gap.
Overlaid .vbo files. Blue is Vbox; red is Track Precision.
Ok, I'm going to go put a cool towel on my forehead; this was too much data!
Yes, I would also like to resolve your difference over time... As one said, "A man with a Rolex may always be sure of the time. A man with two Rolexes is never sure..."
__________________ -Peter Krause www.peterkrause.net www.gofasternow.com
"Combining the Art and Science of Driving Fast!"
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Ah, that's a good idea! Yes, there is a match; not 100% but along with knowing where on the route the thick tree cover is, this definitely suggests the GPS signal was lost:
pretty sure it's smoothed GPS Velocity. You have to pick which CAN data the VBOX Lite and Pro pick up. As far as I know, all systems do the same (AIM/Traqmate, etc). You can look at velocity from CAN if you pick it as something that gets recorded, and then look at the trace, just like any other channel of data, but the software uses GPS for the speeds you see in other places.
I know that a Vbox Sport gets velocity information from GPS but where do the more expensive Vbox units get speed from? CAN?
I'm wondering because I was playing with the Vbox Sport today, connected to Porsche's Track Precision app. I exported the data from Track Precision as a Vbox vbo file, copied the .vbo file from the Vbox Sport and compared the two in Circuit Tools. In the screen captures below, the blue line is from the Vbox and the red line is from Track Precision. There are some big spikes in the Vbox data and it's wrong: I wasn't really going 110 mph in my neighborhood! I mapped the spikes and they are from places on my route where there's heavy tree cover; so probably, the Vbox Sport lost coverage for a moment and it resulted in bad data.
Vbox Sport data
Track Precision data
The spike really isn't an issue, as none of the tracks I'm likely to drive at have any tree cover. However, it did make me curious about where a more expensive Vbox gets velocity data from.
The second interesting thing I noticed was the difference in the two .vbo files. I probably should have realized this but the Porsche one includes all the data that comes from the car's ECU, via the Sport Chrono package and its WiFi connection. There's lots of data, each field listed under "[header]". My favorite is "charisma damper"! I don't know if these are standard .vbo data fields but Circuit Tools does show them when you open the Track Precision vbo file; cool.
.vbo comparison: Vbox Sport on the left; Track Precision on the right
Lastly, I noticed that if I overlay the two .vbo files in Circuit Tool they get out of sync over time. If you look at the screen capture above, you'll see that I edited both vbo files so that they start at exactly the same time. (Look at the bottom, under [data]. The second value is time: UTC time on the left in the Vbox file; PDT on the right in Track Precision.) They don't finish at the same time because the Vbox records until the car stops, while Track Precision stopped when I drove across the finish line...but that shouldn't matter; they still should be in sync. Any ideas? Perhaps Circuit Tools uses elapsed time and not absolute satellite time, so if there's missing data, there will be a gap.
Overlaid .vbo files. Blue is Vbox; red is Track Precision.
Ok, I'm going to go put a cool towel on my forehead; this was too much data!
What is your X-Axis? Distance or position?
Edit - nevermind, looks like time actually. Seems like there is something different between how each file is indexed to time - try using a different X-axis and see if they sync back up.
pretty sure it's smoothed GPS Velocity. You have to pick which CAN data the VBOX Lite and Pro pick up. As far as I know, all systems do the same (AIM/Traqmate, etc). You can look at velocity from CAN if you pick it as something that gets recorded, and then look at the trace, just like any other channel of data, but the software uses GPS for the speeds you see in other places.
In AiM you pick the reference channel for speed. GPS is most common today, but you can use whatever you want.
03-18-2016, 01:55 PM
Where does a Vbox get its speed measurement from?
