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Satellite shines on Rolls-Royce

The ultra-swanky new Wraith uses GPS maps to achieve unprecedented driving performance. Adrienne Harebottle discusses the car’s Satellite Aided Transmission in an interview with Philip Harnett, the Wraith Project Manager

From the pinnacle of high performance to the realm of ultra-luxurious comfort, Philip Harnett left the world of Formula 1 to join Rolls-Royce. The engineer is the project manager for Wraith, arguably the automobile marque’s best grand touring car. I’m sure it’s not necessary to talk about why this luxury vehicle is impressive – what other car brand can be substituted in the expression “it’s the Rolls-Royce of…”? But what is under focus here is the new Wraith’s SAT system, with the acronym standing for: Satellite Aided Transmission.

Harnett gives a breakdown of this system, covering its development, the team behind it and how this very cool satellite-related technology has been used.

How does the SAT system work?   

SAT uses GPS data to ‘know’ where the car is and what is about to come. It does that by superposing the car’s location and meshing that data with the digital mapping system available within the navigation system. The gearbox’s SAT module then determines what course of action it should be ready to make depending on the topography of the digital roadmap it has at its disposal. The system is almost completely internal, with the only external data being received by the high performance GPS receivers built into the car’s infrastructure. Additionally, SAT also takes information from the accelerator to take account of how the car is being driven. Using all this information it pre-selects the right gear, for example for the exit of a bend on a sweeping Alpine pass, in town when leaving a roundabout or when entering a motorway from a slip road.

From where do you get the GPS maps?

The GPS digital road maps are sourced from BMW Group’s trusted digital mapping supplier Navteq bzw. Nokia.

How is the data in the GPS maps used?

SAT accesses the topographical data stored in the digital maps to assess the nature of the road, detecting altitude changes both in inclines and descents, as well as turn intensity, from mild sweeping corners to sinuous hairpins. It also detects roundabouts, junctions and motorway entrances and exits.

How is this data stored? What is the car’s storage capacity?

The digital mapping data is stored in the car’s main memory drive, which has a 20GB capacity.

What about refreshing the maps?

For added accuracy, the GPS refresh frequency has been optimised to deliver a very high refresh rate.

How long did it take to develop SAT and who was involved?

It was a development by a small group within the in-house power train research and engineering team. They worked closely with colleagues who develop the GPS technology. It took two years from the first idea to developing a concept which could then be taken on by the series development team. This was from 2009 to 2011. It then took about a year and a half to make it into series production.

How did this concept come about?

It was demonstrated to me very shortly after I had begun work as Wraith Project Manager in 2009. I automatically realised that the nature of SAT fits quintessentially within the spirit of effortlessness that Wraith achieves. It offers the direct benefits of self-actuated gear changes without any input required from the driver. Therefore, it delivering new age-led dynamic performance with minimal driver input, remaining true to Rolls-Royce hallmarks of effortless dynamics.


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