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In looking at plots of car position in the Track Precision App (TPA), the data looks "chunky" in turns. I assumed I was getting a low data x-fer rate from my Dual GPS puck. Fixed that to 10 Hz, but am seeing the same chunky lines. Exported TPA data to a .vbo file and it looks the same in Circuit Tools (I added the circles on top of the Circuit Tool output). Copied the data from a .csv data export and pasted that into a web app that plots points, and now I am very confused. See images below. The TPA and Circuit Tools plots look like the data points are far apart, thus chunky. But, when I paste the data points, I see that the chunky straight lines are actually made up of lots of points. See plot on right.
This is confusing. If the GPS data points are real, they should show a nice, physically realistic curve. Here's another zoomed in view of part of the track (I added the yellow lines). You can see a straight line segment made up of 10 points. It must be interpolating between the end points of this segment or something, because the car does not move like this.
I was hoping to be able to accurately see the line I am driving, but this is disappointing.
Anyone have any thoughts? I suppose VBox and AIM tools don't give you chunky results...
There area couple of things going on. Not all 10 Hz GPS data is the same.
Then their is smoothing that goes in most software that is not always apparent, able to be changed, or displayed (or even matters).
But, what I think you are really seeing is the actual GPS points with no interpolation in between. Say that was a 60 mph corner (constant speed for ease of analysis). 60 MPH is roughly 90 ft/sec. Divide by ten and you're only getting a measurement every 9 feet. Those are the points you are seeing. Many (most?) systems and software then use the accelerometers and other data to fill in the points in between.The better the system, the better they usually do it (there is lots of math in there to do it correctly).
Time to add the officially supported VBOX Sport to fix this. 20 Hz.
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There are a couple of things going on. Not all 10 Hz GPS data is the same.
Then their is smoothing that goes in most software that is not always apparent, able to be changed, or displayed (or even matters).
But, what I think you are really seeing is the actual GPS points with no interpolation in between. Say that was a 60 mph corner (constant speed for ease of analysis). 60 MPH is roughly 90 ft/sec. Divide by ten and you're only getting a measurement every 9 feet. Those are the points you are seeing. Many (most?) systems and software then use the accelerometers and other data to fill in the points in between.The better the system, the better they usually do it (there is lots of math in there to do it correctly).
Edit. I said 90 ft/ sec, but meant 53.3 knots
Thanks! I was thinking of doing the mph/distance calcs. That turn is a bit slower than 60 mph, but I'll look and see. I also sent the question and images to Dual tech support. I'll post if they answer!
Thanks! I was thinking of doing the mph/distance calcs. That turn is a bit slower than 60 mph, but I'll look and see. I also sent the question and images to Dual tech support. I'll post if they answer!
MPH to ft/s is 150% in rough terms. 60 mph is 90 ft/s. 100 mph is 150 ft/s. I think it's actually 151.5% or something, but I can't remember that.
03-19-2019, 11:29 AM
GPS Track Data and PTPA
