A single unit on the roof measures the path and the drift angle, then sends them to the phone over Bluetooth. It runs on its own battery: nothing plugs into the car.
A prototype in progress
The unit isn't manufactured or sold yet. Its software is written and runs in simulation, and the hardware prototype is in preparation. It has no price and no release date. In the meantime, the app works with just your phone.
The principle
The unit, the phone and the satellites
The unit, mounted on the roof: GNSS RTK receiver, gyroscope, computer and battery, all in one piece.
Two antennas, about 30 cm apart: they give the body's heading.
The positioning satellites, picked up by both antennas.
Bluetooth: the measurements go to the phone, 20 times a second.
The phone, on its mount: the app displays, scores and records.
The RTK corrections from the Centipède network, received through the phone's mobile connection and relayed to the unit.
What it measures
The true angle, not an estimate
Position, to the centimetre
A GNSS RTK receiver tracks the unit to the centimetre, 20 times a second, thanks to corrections from the Centipède network.
The body's heading
The two antennas give the direction the car is pointing. Compared with the direction of its path, it gives the drift angle: measured, not inferred.
Rotation and acceleration
A gyroscope measures the body's rotation speed, and so the sharpness of transitions, and fills in the moments between two GNSS measurements. The accelerations give the lateral g.
Referenced to the rear axle
The unit's position on your car, entered in the vehicle profile, references all the measurements to the rear axle. So two cars can really be compared.
On the roof
One piece, self-contained
A single unit holds everything: the computer, the GNSS receiver, the two antennas under a plastic cover, the gyroscope and the battery.
It mounts rigidly on the roof, so that the gyroscope follows the body exactly.
Nothing plugs into the car: no socket, no wiring harness.
The prototype aims for a full day of driving on its battery.
Wireless
The phone is the link
The unit sends its measurements to the phone over Bluetooth. The app can also reach it over Wi-Fi, through the hotspot.
The RTK corrections go through the phone's mobile connection: no base station to install at the side of the track.
It pairs with your phone using its QR code or its serial number.
Black box: it keeps everything raw on its microSD card, so runs can be recalculated later.
Where it stands
An update on the prototype
The unit's software and the app are written, and tested together in simulation: the simulated unit runs on a PC and talks to the app with the same protocol as the real one.
The hardware prototype is in preparation: it isn't assembled yet.