Satellite based train location Peter Gurnk Oldich Trgl

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Satellite based train location Peter Gurník, Oldřich Trégl 14 -15. 3. 2005 CGSIC European

Satellite based train location Peter Gurník, Oldřich Trégl 14 -15. 3. 2005 CGSIC European meeting

Content § Why want we use GNSS? û Possible hazards of using GNSS Safety

Content § Why want we use GNSS? û Possible hazards of using GNSS Safety Requirements GNSS implementation Conclusion û û û 14 -15. 3. 2005 CGSIC European meeting 2

Why want we use GNSS? n n Train location is key information for rail

Why want we use GNSS? n n Train location is key information for rail transport control Track circuits – classical concept Train position in line segment – low accuracy ¨ Trackside wires are needed – not cost effective ¨ Fixed block – low efficiency of using line ¨ ATO is hardly applicable without additional technology ¨ 14 -15. 3. 2005 CGSIC European meeting 3

Why want we use GNSS? n New concept – passive balise + odometry Technology

Why want we use GNSS? n New concept – passive balise + odometry Technology supported in ERTMS project - all corridor lines in Europe will be equipped with balises – future interoperability ¨ Passive point device - no trackside wires are needed ¨ High precise positioning – control centre has real-time information ¨ Possibility of using moving blocks – higher density of train transportation ¨ 14 -15. 3. 2005 CGSIC European meeting 4

Why want we use GNSS? n Balises vs. GNSS positioning ¨ Some countries (Russia,

Why want we use GNSS? n Balises vs. GNSS positioning ¨ Some countries (Russia, Australia) refused to join in ERTMS project because of high cost n ¨ Implementation of ERTMS in Europe could be faster if cheaper technology would exists n ¨ In average 2 balises per km are needed Virtual balise concept – integrating GNSS into ERTMS-ETCS could spare some balises on the track We need to find a cheap solution for low density lines n n Efficiency of control suburban lines is low Safety could be improved ¨ ¨ 14 -15. 3. 2005 Poor equipped lines – mostly no track circuits Information about train position - based on voice communication CGSIC European meeting 5

Content ü Why we want to use GNSS? § Possible hazards of using GNSS

Content ü Why we want to use GNSS? § Possible hazards of using GNSS û Safety Requirements GNSS implementation Conclusion û û 14 -15. 3. 2005 CGSIC European meeting 6

Possible hazards of using GNSS n GNSS space segment ¨ n GNSS control segment

Possible hazards of using GNSS n GNSS space segment ¨ n GNSS control segment ¨ n Faulty satellite can cause unboundary error of train position TTA is not guaranteed Examples from past Faulty navigation message data – SVN 35, 1997 ¨ Satellite clock error – PRN 22, 2001 ¨ 14 -15. 3. 2005 CGSIC European meeting 7

Possible hazards of using GNSS n Transmission SIS ¨ Low availability: canyons, tunnels, forests

Possible hazards of using GNSS n Transmission SIS ¨ Low availability: canyons, tunnels, forests n High availability in stations is needed – poor visibility (urban area) Multipaths – common in canyons and on the bridges upon the lakes / rivers (reflexive surface) ¨ Atmospheric delays ¨ Jamming – weak signal – easy to jam ¨ n 14 -15. 3. 2005 Authenticity of message have to be proved CGSIC European meeting 8

Possible hazards of using GNSS n Using commercial GNSS receiver Possible systematic error in

Possible hazards of using GNSS n Using commercial GNSS receiver Possible systematic error in HW/SW ¨ Problematic determination of position ¨ n Iterative methods ¨ ¨ n Stability ¨ n Some algorithms are unstable in some cases Digital filters ¨ ¨ 14 -15. 3. 2005 Error could transfer to following fixes Undetected error can expose for relative long period of time Based on statistical methods Some errors could remain masked CGSIC European meeting 9

Content ü Why we want to use GNSS? Possible hazards of using GNSS §

Content ü Why we want to use GNSS? Possible hazards of using GNSS § Safety Requirements û GNSS implementation Conclusion ü û 14 -15. 3. 2005 CGSIC European meeting 10

Safety Requirements n Safety integrity ¨ n Ability of a safety-related system to achieve

Safety Requirements n Safety integrity ¨ n Ability of a safety-related system to achieve its required safety functions under all the stated conditions within a stated operational environment and within a stated period of time n SIL - a number which indicates the required degree of confidence that a system will meet its specified safety functions with respect to systematic failures Standards ¨ EN 50126 EN 50129 EN 50128 ¨ EN 50159 -2 ¨ ¨ 14 -15. 3. 2005 RAMS Electronic systems for signalling Software for railway control and protection system Safety related communication in open transmission systems CGSIC European meeting 11

Safety Requirements n Single faults (EN 50129) ¨ n “It is necessary to ensure

Safety Requirements n Single faults (EN 50129) ¨ n “It is necessary to ensure that SIL 3 and SIL 4 systems remain safe in the event of any kind of single random hardware fault which is recognized as possible. ” Reactive fault-safety (EN 50129) ¨ “Maximum total time taken for detection + negation shall not exceed the specified limit for the duration of a transient, potentially hazardous condition. ” 14 -15. 3. 2005 CGSIC European meeting 12

Safety Requirements n common-cause failures (EN 50129) ¨ “In systems containing more than one

Safety Requirements n common-cause failures (EN 50129) ¨ “In systems containing more than one item whose simultaneous malfunction could be hazardous, independence between items is a mandatory precondition for safety” 14 -15. 3. 2005 CGSIC European meeting 13

Safety Requirements n GNSS receiver firmware ¨ By the EN 50128 is classified as

Safety Requirements n GNSS receiver firmware ¨ By the EN 50128 is classified as “COTS software” ¨ Requirements for COTS software: n n n “A strategy shall be defined to detect failures of the COTS software and to protect the system from these failures” “The protection strategy shall be the subject of validation testing” “As far as practicable only the simplest functions of the COTS software shall be used” Þ It’s very hard to accept information's from commercial GNSS receiver firmware! 14 -15. 3. 2005 CGSIC European meeting 14

Content ü Why we want to use GNSS? Possible hazards of using GNSS Safety

Content ü Why we want to use GNSS? Possible hazards of using GNSS Safety Requirements § GNSS implementation û Conclusion ü ü 14 -15. 3. 2005 CGSIC European meeting 15

GNSS implementation n Integrity Monitoring ¨ Main goal is avoid using faulty satellites in

GNSS implementation n Integrity Monitoring ¨ Main goal is avoid using faulty satellites in position calculation ¨ WAAS/SBAS n Integrity information from WAAS/SBAS will be transferred to train using radio channel – because of poor visibility of GEO in real terrain ¨ LAAS n n 14 -15. 3. 2005 Local monitor station – stationary receiver with good visibility of satellites Only positive confirmed satellites can be included to position calculation in mobile unit CGSIC European meeting 16

GNSS implementation n Odometry – why is useful? ¨ To improve availability n ¨

GNSS implementation n Odometry – why is useful? ¨ To improve availability n ¨ In some areas (tunnels, canyons, forests) there are still low number of visible satellites – we cant guarantee the integrity or we are unable to compute position To improve precision n 14 -15. 3. 2005 In some areas an odometry CI is better then CI derived from GNSS data processing CGSIC European meeting 17

GNSS implementation n Accuracy ¨ For resolution of parallel track – high accuracy is

GNSS implementation n Accuracy ¨ For resolution of parallel track – high accuracy is needed Þ High accuracy GNSS positioning method (D-GNSS), or Þ Using additional location-oriented devices in station • Balises 14 -15. 3. 2005 CGSIC European meeting 18

Content ü Why we want to use GNSS? Possible hazards of using GNSS Safety

Content ü Why we want to use GNSS? Possible hazards of using GNSS Safety Requirements GNSS implementation § Conclusion ü ü ü 14 -15. 3. 2005 CGSIC European meeting 19

Conclusion n GNSS could be solution for low density lines ¨ Technology for low-cost

Conclusion n GNSS could be solution for low density lines ¨ Technology for low-cost positioning is needed ¨ Effort to improve safety n Future integration to ETCS ¨ Concept n of virtual balises Non safety-critical applications ¨ Conflict-avoiding systems ¨ Information system for passengers and management n 14 -15. 3. 2005 Real-time tracking of trains CGSIC European meeting 20

Thank you Ing. Peter Gurník n gurnik. peter@azd. cz Ing. Oldřich Trégl n tregl.

Thank you Ing. Peter Gurník n gurnik. [email protected] cz Ing. Oldřich Trégl n tregl. [email protected] cz www. azd. cz