Hyppää pääsisältöön

Stefan Söderholm: “Why doesn’t GPS show my correct position?”

Tampereen yliopisto
SijaintiKorkeakoulunkatu 1, Tampere
Hervannan kampus, Tietotalo, auditorio TB109 ja etäyhteys
Ajankohta13.10.2023 9.00–13.00
PääsymaksuMaksuton tapahtuma
For the last three decades, satellite navigation has evolved from being a technology for professional and military users to a technology available for everyone. In his doctoral dissertation, Ph.Lic (Physics) Stefan Söderholm assessed the impact of the evolution of GNSS technology on the performance and design of consumer grade GNSS receivers. According to him, there has been a significant performance improvement due to the introduction of more signals as well as the introduction of new modern modulation techniques and positioning methods, and we have not seen the end of it yet.

The evolution of satellite navigation over the last two decades has had a revolutionary impact on everyday life. Satellite navigation has allowed people to travel more quickly, use a never-ending range of location-based services, access information more quickly, and track our deliveries. It has allowed companies to operate more efficiently, reduce operational costs and improve customer service. The next phase of this ongoing evolution will provide users with better accuracy, higher reliability, and better security enabling even more services and applications.

Stefan Söderholm’s research spans over a period of more than 15 years, aligned with the evolution of satellite navigation. The main goal in his thesis was to first assess the impact this evolution could have on the performance of consumer grade receivers and next address the implications this would have on receiver architecture.

“It has been a privilege to follow the introduction of satellite navigation into everyone’s life, understand the challenges and opportunities, and contribute to the impact it has had on society. There is so much more to be done, and I am proud to still be a part of it,” Söderholm says.

The future of satellite navigation for consumers

Over the last ten years two new global navigation systems, the European Galileo and the Chinese Beidou systems, have become operational and the Russian GLONASS system has had a significant facelift. Several new regional systems have also been introduced. As a result, the number of satellites has increased from 30 to almost 150 and the satellites of today transmit better and more accurate signals to the user and finally also high precision techniques are within reach for the nonprofessional users.  

In his research Söderholm showed that by using these new signals and combining information from multiple navigation systems, both availability and accuracy of the receiver can be drastically improved. In places with high buildings like cities for example, the position error can be reduced to less than a tenth, and the fix availability can be more than twice higher. Söderholm also presented new techniques for processing the new signals that could further improve the accuracy by a factor of 5 and finally he addressed the performance of consumer grade receivers using high precision techniques.

“Many of the presented methods and improvements are simply not yet available in consumer grade receivers. I strongly believe that over the next 5-10 years we will still see a significant improvement in both accuracy and availability enabling new applications and services for anyone using satellite navigation,” Söderholm adds.

In addition to looking at the possible improvements, Söderholm also addressed the challenges the receiver manufacturers are facing when having to support more complex information and processing techniques and he presented some alternative receiver architectures that could replace the more traditional ones.

“Receiver manufacturers for the consumer market will always need to make compromises and therefore it is essential to understand the impact of new signals and methods and find the best price/performance ratio. In some cases, for example, a software defined receiver might be a better choice than using purely hardware-based building blocks,” Söderholm says.

Stefan Söderholm currently works as the Group manager of GNSS Components at Septentrio and as the General Manager of Septentrio Finland Oy.

Public defence on Friday 13 October

The doctoral dissertation of Ph.Lic (Physics) Stefan Söderholm in the field of Information Technology titled Methods for improving performance in consumer grade GNSS receivers will be publicly examined at the Faculty of Information Technology and Communication Sciences at 12:00 on Friday 13 October 2023. The venue is Hervanta Campus, Tietotalo buiding, auditorium TB109 (Korkeakoulunkatu 1, Tampere). The Opponents will be Doctor Anna Jensen from AJ Geomatics and Professor Emeritus Terry Moore from University of Nottingham. The Custos will be Professor Jari Nurmi from the Faculty of Information Technology and Communication Sciences, Tampere University.

The doctoral dissertation is available online.

The public defence can be followed via a remote connection.

Photograph: Ulrika Söderholm