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Building a high precision race track telemetry system using RTK GPS (Part 1)

How do you get faster as a racing driver? A lot of it is by feel. However, from karting to Formula 1, if you are racing at the highest levels you need to be analyzing your driving data to find those last tenths and understand how setup changes affect lap time.

Lap time

The most basic form of telemetry is lap time. At the end of the day, all your setup changes and driving inputs are reflected in your lap times. At most race or kart tracks, you can see your laptimes after a session, however this really isn’t optimal. Even laptimes from a lap timer in your car or kart, shown to you after a lap, aren’t enough to really extract everything from a lap and understand where your time is going. That’s where live timing is really useful.

Live delta

Live timing gives the driver a real-time delta, at every moment throughout a lap, when compared to a reference lap. While extremely useful, you need a track where emitters are placed around or under the tarmac to be able to interpolate your position accurately. F1 tracks have this, but not your local karting track.

Current solutions

GPS based lap timers exist (mychron5, alfano 6), but the accuracy from a single gps chip can’t be less than 1-2 meters. Enough for lap and sector times, but not live deltas. You can’t see the effect of braking a little bit later, or having a smoother turn in, slight difference in line, etc… You can have an idea of the time gained or lost on the following straight by looking at the approximate lap time, but you don’t have cause and effect. Live deltas give you that cause and effect and really helps your brain understand what caused the gain or loss.

High precision GPS

In the past few years, the cost of RTK gps systems has really gone down, allowing centimeter level accuracy for a couple hundred dollars. Chips like the uBlox F9P, in can give you 1cm accuracy at 20Hz.

Base and Rover configuration

For RTK to work you need 2 GPS chips, one sending corrections to the other. A common configuration is base and rover, where you fix a base at a known location, and then the rover can know its absolute position with centimeter accuracy. If you don’t have the exact location of the base, you can still know the relative accuracy. In fact, that’s all we need for live delta.

Expect more posts on this project shortly!