GPS has become somewhat of a buzz word in karting data analysis since AIM introduced it on the Mychron 4. Many have waxed lyrical about its application and usefulness to determine driver performance (braking, lines, corner speed) but how accurate is it really;
Generally speaking GPS devices are accurate to within 15m (just look at your phone’s GPS). Some devices also incorporate WAAS (Wide Area Augmentation System) which can get the accuracy down to 3m, but still not good enough for karting. Accuracy can be further increased by using GPS/INS.
GPS/INS is the use of GPS signals and inertial navigation systems (INS). INS is the combination of accelerometers, gyros etc. If it is being used as an integrated INS/GPS, which allows the INS to interpolate the data between GPS samples, producing a higher data rate than what the GPS receiver can do on its own, and the GPS is used to null the errors in the INS then it is possible to increase the accuracy. These systems are used on aircraft, missiles and increasingly in some automotive test applications to determine roll, slip etc.
However this really only gets the accuracy down to 2m, still not good enough for karting.
VBox Automotive, a data acquisition manufacturer for the automotive industry claim much higher accuracy;
"GPS positional accuracy is subject to ionospheric interference, which causes a satellite signal to change in length as it travels towards the Earth’s surface. This means that, depending on the quality of the receiver, accuracy can vary by several metres.
VBOX data loggers are fitted with superior GPS engines that give better positional accuracy than those found in mobile phones and satellite navigation devices. By using additional signals other than those from the standard US GPS satellites, this can be enhanced further. The free SBAS services augment the positional capabilities of a survey-grade receiver to as good as 1m without the use of a Base Station.
However, by adding another GPS engine at a fixed position, the majority of errors can be calculated and removed from the final result. This is the function of a Base Station: because it remains stationary, it is able to broadcast correction messages to a roving VBOX, resulting in much improved positional accuracy.
By incorporating signals from the Russian GLONASS satellite constellation and employing a Real-Time Kinematic (RTK) algorithm, the VBOX 3i Dual Antenna RTK with suitable Base Station achieves a positional accuracy of +/-2cm."
I happened to use one of these systems at university, and sure they are accurate, but they were also £25,000. The price may have come down but they are still, I would assume, outside of the realms of most karters, plus they wouldn’t fit on a kart, the two GPS receivers need to be 2.5m from each other.
So the question is, have we been duped? Are we accepting lower levels of data fidelity for a buzz word? Why do the Tonykart factory team use a none GPS system? Or should we all go buy an ebox and all the extended sensors. Maybe AIM could tell us?
My personal opinion, GPS data is good but only when backed up by a suite of physical sensors and when combined with the correct physical sensors one can set up the kart without talking to the driver