The advantages of using GPS for Predictive Lap-timing

Traditionally, circuit data-logging systems have used rolling distance around the lap as a reference to compare two different laps. This method relies on the line the driver takes around the lap being very similar; otherwise the alignment will get progressively worse as the lap unfolds. In some cases this method works fine, but when a driver wants to try a different line, overtakes another car, or the circuit is fairly long, then it becomes difficult to obtain a meaningful alignment.

With the advent of fast updating GPS data-loggers, an alternative method is to use the GPS position to align the two laps. Whilst GPS position may only be accurate to a few metres, a typical average race speed would be well in excess of 30m/s, minimising any errors to around 1/10^th of a second. In fact this method is already in use in many products to get accurate lap-times, using a single start/finish line, where accuracies usually better than 1/10^th of a second are regularly achieved.

To see how this can help in the analysis software, we can take the two best laps during a race from a professional driver around Silverstone National Circuit (2.6km). The rolling distance variation was 11.6m even though the lap-time difference was only 0.06s. This equates to an analysis alignment error of 0.3s, and this is around a very short track, with a very good driver. On a longer track with a less consistent driver, this error can easily grow to over 1s!

However, by using GPS position, the timing error between these laps was virtually eliminated.

A recent development has been to take this GPS positional alignment and use it inside the car, in real time. Predictive lap-timers are not new, but traditionally they have used the potentially imprecise rolling distance alignment method to show the driver if the current lap is slower or faster than their previous best. In F1 this is referred to as the driver’s ‘delta’ time.

As processors have become faster, and the routines have been optimised, GPS has become a more accurate method of achieving alignment in real time, updated 10 times a second. Racelogic have made this functionality available with their OLED Display. When combined with the Video VBOX, the predictive lap-timing will stay accurate to within 1/10^th of a second, no matter how long the lap or what lines the drivers take.

 

 

For instant feedback on driving technique and line, this kind of predictive display cannot be beaten, and as prices for this kind of equipment have fallen, displays such as these will become an essential tool for any driver keen on improving lap-times.