The path to mass market high precision positioning: Page 4 of 6

November 20, 2018 //By Thomas Nigg, u-blox
The path to mass market high precision positioning
If we’re going to see fully autonomous vehicles on our roads, a number of technologies need to hit maturity and then be rolled out simultaneously. Key among them is high precision positioning capability that’s reliable, affordable and scalable.

SSR-based techniques, on the other hand, send out one stream of data that covers the full service area, and can be picked up by any rover. Thanks to this simpler communication approach, and the fact that you only need a reference station every 150-250 km, SSR is the only technique that can feasibly be used for mass market high precision positioning, including highly assisted driving.


Figure 2: These graphs show the performance improvement you get when using dual-band GNSS with SSR correction data, compared to single-band GNSS on its own.

Moreover, we’ll see even better performance as improved receiver hardware, able to pick up more data from satellites, is rolled out. Early GNSS satellites transmitted in just one frequency band. More modern ones use up to three: GPS, for example, sends out its signals in L1 (centered on 1575 MHz), L2 (1227 MHz) and L5 (1176 MHz). BeiDou and GLONASS both use L1 and L2. High precision receivers can benefit by using more than one frequency band from the same constellation, thereby significantly accelerating the speed at which they can achieve a highly precise reading. Ultimately, this results in a more robust and reliable location service.

High-precision GNSS systems of the future will be made up of a range of components working together. Firstly, you’ll have the existing satellite constellations. Second, there will be the reference base stations, logging the satellite signal errors in real time. Third are the correction services, which transmit the error components, via the Internet and geostationary satellites. And fourth will be the kit in the rover devices, including dual-band GNSS receivers, a cellular modem (to pick up correction data sent over the Internet), and an L-band receiver (to collect the correction data from the geostationary satellites).

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