Introduction of GNSS for Virtual Balise Detection in ETCS

Issue/Revision: 1.0

Reference: ESA-IAGW-Presentation

Status: N/A

ESA UNCLASSIFIED - For Official Use

Christian Wullems (Christian.Wullems@esa.int)

SoL Applications of GNSS in Railway

1. Key SoL applications of GNSS in future evolutions of ERTMSa. GNSS for detection of Virtual Balises foreseen in next evolutionb. The future? GNSS for on-board integrity proving and virtual track circuit

ERA Future Evolution of ERTMS and Roadmap (22nd September 2015, ERTMS Control Command and Railway Communication Conference 2015)

Towards GNSS Mission Requirements GNSS for virtual Balise detection

1. Important to agree on operational scenarios for use of virtual balise detection before consolidating GNSS architectural options

a. Progressing in NGTC

2. Need to be pragmatica. What features of ETCS can we use to reduce requirements on GNSS

integrity to the lowest practicable?

Safety Analysis

Operations Concept

Operating Scenarios

Virtual Balise Principles

Mission Profiles

GNSS Integrity

Requirements

Application Conditions

ETCS Enhanced Architecture for Virtual Balise

Source: UNISIG SUBSET-026-4

GNSS Integrity RequirementsExample of Application Conditions to Restrict Use of Virtual Balises

1. Reliance on unlinked balise groups for announcement of information that if missed could lead to a hazardous consequence (e.g. TSR)

a. Maximum failure rate of 1.75E-11 / hour for information point to be undetectable due to technical failures

b. To meet target: 2 balise groups of at least 2 balises required assuming independence

2. Virtual balise detection with GNSSa. Cannot assume independence between virtual balises detected with

GNSS only (i.e. max 12m between balises within a group)b. Correlated conditions affecting availability

Single balise unavailability < 2.0E-5 / hour

GNSS Mission Requirements [all operations]SIS misleading information THR

Barriers against local feared events

Residual risk of misleading information

Barriers against system feared eventsAchievable risk reduction with augmentation (e.g. SBAS, GBAS, etc.)

Impact on ETCS operations with virtual baliseWhat features of ETCS can we use to reduce GNSS integrity to the lowest practicable?

Impact on positioning performance (e.g. avail, accuracy), VBR cost, complexity, certification, level of prescriptionWhat is needed to meet THR?(e.g. independent sensors, multi-frequency, etc.)

Performance of augmentation systemsAre performances of existing systems translatable / applicable to railway?

Towards GNSS Mission Requirements GNSS for virtual Balise detection

Feared events leading to misleading information hazard

Magnitude of risk reduction required to meet THR

Conclusions

1. Key Messagesa. Consolidation of operational scenarios for use of virtual balise

detection is fundamental to drive architectural options– Specific working group in NGTC setup for this

b. Be pragmatic… integrity requiment of 10E-9 / hour is VERY DEMANDING

– It is really our target for GNSS? – Specific ERTMS scenarios allow less demanding requirements

c. Once GNSS requirements are agreed, – Specification of GNSS mission requirements needs to come from

an iterative process considering targets and understanding of:– System capabilities (incl. augmentation)– Challenges of the environment