GNSS – Why is it useful for RaceDirector?
In this article I describe why GNSS is important to RaceDirector. The basis for a good user experience is as exact position data as possible. But where to take from, if not steal? GNSS stands for Global Navigation Satellite System and is the umbrella term for all existing navigation systems like GPS, Galileo, GLONASS and BeiDou.
GNSS vs. GPS
When we think about satellite navigation, we always talk about GPS. Sure, it was the first system available worldwide. Meanwhile, there are other functioning systems from Russia, China and Europe. While the term GPS is still used in the context of satellite positioning, you have to look closely to see which system is actually used. For example, a GNSS data logger in China will most likely use a chip that uses the BeiDou system.
GNSS is not GPS. GPS is only part of GNSS
When recording the position data, basically all GNSS can be used. Which system is actually used depends on the region (Europe, North America, South America, China, Russia, Asia, Australia) where the data is recorded. If the racetrack is e.g. in China, the data loggers can use the Chinese system BeiDou. A simultaneous use (Multi GNSS) and recording of several GNSS is also possible – this depends on the loggers and their chip sets. Basically, the more satellites the higher the accuracy of the position data.
SBAS – Little helper with great influence
The accuracy can be increased by additional technical functions. Meanwhile, consumer loggers also use SBAS (Satellite Based Augmentation System). SBAS provides additional information (correction information) emitted by geosynchronous (mostly geostationary) satellites, increasing the reliability, accuracy and availability of positioning. Depending on the region, there are different SBAS satellite systems:
SBAS comes originally from aviation, but is now also used for civil navigation. If SBAS is available – you need a contact to these satellites and a logger with a chip that supports it – accuracies up to 1.5 meters can then be achieved .
Sampling Rate
Another important technical feature of the logger is the sampling frequency. How many times per second are position data queried and recorded? Depending on the application, the frequencies range from 1x per minute (1Hz) to 20x per second (20 Hz). With data loggers for the monitoring of a fleet, it is sufficient if the position is queried once every 10 minutes. For fast moving objects (> 50 km / h) and in real time, the sampling frequency must be at least 4 Hz (4x per second). Otherwise, too few position points would be recorded and the representation of the driven line would not be correct.
In motorsport at least 4Hz sampling frequency are necessary
In summary, it can be stated that today all the necessary technologies are available to the end users worldwide, which means that accuracies of up to one meter can be achieved, at best. Of course that’s good but not perfect yet. But even if the demands are in the centimeter range, there are now solutions that can be realized without great financial expense. Here then come technologies, such as Correction of raw GNSS data for use. Actually, it behaves similarly, as with SBAS only, that it includes more data for the correction.
Author: OJ
