Publication date: 
2022/09/22
Multi-frequency satellite receivers using various satellite systems, mainly Galileo in addition to GPS, will help to refine the position of Prague trams. Thanks to this, their accuracy even in the dense development of the centre of Prague is very high, showing deviations of no more than 2 metres. They should be installed in all trams in regular service by the end of next year. The project with the Transport Company of the Capital City of Prague (DPP) is being worked on. The project was carried out by scientists from the Faculty of Electrical Engineering.

The multi-frequency satellite receivers that DPP is now installing in its trams are capable of receiving signals from various global positioning satellite systems (GNSS), not only GPS, operated by the United States Space Force (USSF), but especially from the European autonomous Galileo system, which can significantly improve positioning accuracy. Both satellite navigation systems provide the services needed to ensure localisation free of charge.

The configuration and setup of the new devices is the result of a DPP pilot project aimed at upgrading existing satellite receivers in Prague trams using only GPS signals, which has been running since 2019 in cooperation with the Prague City Hall, and European Global Navigation Satellite System Agency (GSA), transformed last year into the European Union Space Programme Agency (EUSPA). The precise localisation of trams will not only improve the overview of the current traffic situation for dispatchers and passengers, but will also open up opportunities for further savings in vehicle and infrastructure operations thanks to new possibilities for optimising the journey.

„Díky spolupráci s vědci a odborníky z Fakulty elektrotechnické ČVUT, Agentury Evropské unie pro kosmický program a Ministerstva dopravy jsme konečně našli řešení pro určování přesných poloh pražských tramvají. Díky detailním analýzám, které z výsledků zpracovali vědci z Fakulty elektrotechnické ČVUT, se nám podařilo najít nejvhodnější typ satelitního přijímače, a to s využitím evropského navigačního systému se signálem GNSS. V rámci testovacích jízd vykazoval jen minimální odchylky polohy, maximálně do 2 metrů,“ řekl Adam Scheinherr, náměstek primátora hl. m. Prahy pro oblast dopravy a předseda dozorčí rady DPP.

"Thanks to the cooperation with scientists and experts from the Faculty of Electrical Engineering of the Czech Technical University in Prague, the European Union Space Programme Agency and the Ministry of Transport, we have finally found a solution for determining the exact positions of Prague trams. Thanks to detailed analyses of the results by scientists from the Faculty of Electrical Engineering of the Czech Technical University, we have managed to find the most suitable type of satellite receiver, using the European GNSS navigation system. During the test runs, it showed only minimal position deviations, up to a maximum of 2 metres," said Adam Scheinherr, Deputy Mayor of the Capital City of Prague for transport and Chairman of the DPP Supervisory Board.

„Zastaralé satelitní přijímače v tramvajích pro určení přesnější polohy vozidel využíváme zhruba 20 let, fungují pouze na systému GPS. V husté zástavbě v centru Prahy nicméně tyto přístroje velmi často vykazovaly a vykazují značné odchylky od skutečné aktuální polohy v řádu desítek až stovek metrů, což je nevyhovující pro další rozvoj moderních aplikací v MHD včetně PID Lítačky. Proto jsme v roce 2019 ve spolupráci s hl. m. Prahou, EUSPA a odborníky v této oblasti z Fakulty elektrotechnické ČVUT pod vedením profesora Františka Vejražky a Ing. Václava Navrátila zahájili pilotní projekt s cílem nejen modernizovat stávající přijímače, ale najít takový typ a jeho konfiguraci, který by obstál v provozu tramvají ve specifických podmínkách centra Prahy. V průběhu projektu jsme otestovali různé typy vícefrekvenčních přijímačů, s každým z nich jsme absolvovali desítky testovacích jízd v běžném provozu,“ uvedl Milan Slunečko, vedoucí jednotky Správa vozidel Tramvaje DPP a dodal: „Původní přijímače postupně měníme za nové, tyto práce realizujeme v rámci plánované údržby nebo oprav jednotlivých vozů. V současnosti jsou nainstalovány ve všech 55 tramvajích typu 14T, 35 vozidlech T3R.PLF a ve většině tramvají KT8N2, tj. zhruba v necelé třetině vozového parku DPP. Do konce roku 2023 je plánujeme nainstalovat do všech tramvají.

"We have been using outdated satellite receivers in trams for about 20 years to determine the exact location of the vehicles, they only work on the GPS system. However, in the dense development in the centre of Prague, these devices very often showed and still show significant deviations from the actual actual position in the order of tens to hundreds of metres, which is inadequate for further development of modern applications in public transport, including PID Lítaka. Therefore, in 2019, in cooperation with the Capital City of Prague, we have developed a new version of the PID. Prague, EUSPA and experts in this field from the Faculty of Electrical Engineering of the Czech Technical University under the leadership of Professor František Vejražka and Ing. Václav Navrátil, we launched a pilot project with the aim not only to modernize the existing receivers, but to find a type and configuration that would withstand the operation of trams in the specific conditions of the Prague city centre. In the course of the project, we have tested various types of multi-frequency receivers, with each of them we have completed dozens of test runs in normal operation," said Milan Slunečko, head of the DPP Tram Vehicle Management Unit, adding: "We are gradually replacing the original receivers with new ones, these works are carried out as part of planned maintenance or repairs of individual cars. At present, they are installed in all 55 trams of type 14T, 35 T3R.PLF vehicles and in the majority of KT8N2 trams, i.e. in about a third of the DPP fleet. We plan to install them in all trams by the end of 2023."

"The development of new applications, the intensity and specifics of Prague's tram traffic place high demands on the accuracy, availability and reliability of precise car localization, which, however, are not met by conventional mono-frequency receivers used, for example, in smartphones. A congested city centre with narrow streets and limited views of the sky is one of the most challenging environments for satellite navigation, so it is necessary to use multiple satellites from different systems, especially GPS and Galileo. The chosen solution and the required parameters of the GNSS receivers are the result of tens of weeks of testing different variants in real operation and detailed analysis of measured data. We are very pleased that DPP approached our team, which has been dealing with satellite navigation for a long time, and we believe that the new GNSS receivers will bring benefits to both DPP and Prague passengers." said Václav Navrátil from the Department of Radioelectronics at the Faculty of Electrical Engineering of CTU.

"The European Union Space Programme Agency has long supported the deployment of the Galileo and EGNOS satellite navigation systems in transport. In addition to their common use by passengers in various transport applications on mobile phones, our navigation services are used, for example, for instrumented approach of aircraft on landing or for precise vehicle location in traffic accidents in the eCall system, where they can help ensure the timely arrival of integrated rescue services. We are pleased that Galileo will also help to improve localization in Prague tram transport and open up space for further innovations and more efficient daily operations," concluded Daniel Lopour from the European Union Space Programme Agency (EUSPA).

Selected parameters of new multi-frequency satellite receivers in Prague trams:

Signal reception from satellite systems: Galileo, GPS, Beidou

Frequencies: L1/E1 and L2/E5b

Position accuracy: more than 95%, maximum deviation 2 metres

Basic technology: GNSS receiver + IMU motion sensors (MEMS)

Test route:

Vozovna Pankrác – Náměstí Bratří Synků – I. P. Pavlova – Náměstí Míru – Korunní – Flora – Želivského – Vozovna Žižkov (smyčka) – Olšanské náměstí – Hlavní nádraží – Florenc – Karlín – Palmovka – Libeňský most – Nádraží Holešovice – Strossmayerovo náměstí – Vltavská - Těšnov – Florenc smyčka – Václavské náměstí – Národní třída – Staroměstská – Právnická fakulta – Malostranská – Královský letohrádek – Pohořelec – Hládkov (spojka) – Královský letohrádek – Malostranská - Újezd – Národní třída – Karlovo náměstí – I. P. Pavlova – Náměstí Míru – Ruská – Čechovo náměstí – Otakarova – I. P. Pavlova – Karlovo náměstí – Albertov - Náměstí Bratří Synků – Vozovna Pankrác

PHOTO courtesy of: DPP - Petr Hejna