SBAS Standards

Fundamentals
Title	SBAS Standards
Author(s)	Edited by GMV, based on ESA EGNOS book SP-1303
Level	Basic
Year of Publication	2011

Introduction

There are two sets of International Standards which SBAS’s shall be compliant in order to be used by Civil Aviation Authorities:

• The Standards and Recommended Practices (SARPS) Standard for SBAS systems established and controlled by the International Civil Aviation Organization (ICAO) and which provides Standards regarding the type and content of data which must be generated and transmitted by an SBAS system. In general, the SBAS provider shall broadcast a SBAS Signal in Space (SIS) compliant to this standard in terms of radio-frequency characteristics, and data content and format.
• The Minimum Operational Performance Standard (MOPS) DO229 established and controlled by the US Radio Technical Commission for Aeronautics (RTCA) and which provides standards for SBAS receiver equipment.

For the aeronautical user international community, the documents listed in the following table constitute the current version of the core set of documents to be used for the development of a new system devoted to provide services to these users or for the development of aeronautical user terminals.

Document Item	Reference	Issue	Date	Standardisation Body
SBAS Elements
SARPS Volume 1 – Annex 10	Including Amendments 1-81	6	July 2206	ICAO
MOPS for GPS/WAAS airborne equipment	MOPS DO-229	D	2006	RTCA SC 159
MOPS for GNSS Airborne Antenna Equipment	MOPS-DO-228	1	January 2000	RTCA SC 159
MOPS for GNSS Airborne Active Antenna for the L1 Frequency Band	MOPS-DO-301	1	December 2006	RTCA SC 159
Primary Constellations
GPS
GPS L1, L2C	IS-GPS-200	E	June 2010	GPS Wing (GPSW)
GPS L5	IS-GPS-705	A	June 2010	GPSW
GPS L1C	IS-GPS-800	A	June 2010	GPSW
GLONASS
GLONASS L1, L2 ICD	GLONASS ICD	5.1	2008	Russian Institute of Space Device Engineering
Galileo
Galileo Open Service SIS ICD	OS SIS ICD	1	February 2010	European Union
MOPS for Airborne Open Service Galileo Satellite Receiving Equipment	ED-TBD	Draft 1.2	December 2010	EUROCAE WG62

Standardization Bodies

ICAO

(Note: most of the informations presented here are extracted from ICAO web site.)

ICAO's Standardization

One of ICAO's chief activities is standardization, the establishment of International Standards, Recommended Practices and Procedures covering the technical fields of aviation: licensing of personnel, rules of the air, aeronautical meteorology, aeronautical charts, units of measurement, operation of aircraft, nationality and registration marks, airworthiness, aeronautical telecommunications, air traffic services, search and rescue, aircraft accident investigation, aerodromes, aeronautical information services, aircraft noise and engine missions, security and the safe transport of dangerous goods. After a Standard is adopted it is put into effect by each ICAO Contracting State in its own territories. As aviation technology continues to develop rapidly, the Standards are kept under constant review and amended as necessary. In keeping pace with the rapid development of international civil aviation, ICAO is conscious of the need to adopt in its specifications modern systems and techniques. In recent years, extensive work has been undertaken by ICAO in the areas of reporting aircraft accident and incident data, all-weather operations, automation of air traffic services, the application of computers in meteorological services, aircraft noise, engine emissions and the carriage of dangerous goods by air. ICAO has dealt with the subject of unlawful interference with civil aviation and with questions regarding aviation and the human environment.

The International Civil Aviation Organization (ICAO)

Creating and modernizing SARPs is the responsibility of the International Civil Aviation Organization, or ICAO, the specialized agency of the United Nations whose mandate is to ensure the safe, efficient and orderly evolution of international civil aviation. ICAO has its headquarters in Montreal, Canada, with seven regional offices throughout the world. From its beginning in 1944 it has grown to an organization with over 180 Contracting States. ICAO's aim is the safe and orderly development of all aspects of international civil aeronautics. It provides the forum whereby requirements and procedures in need of standardization may be introduced, studied and resolved. The charter of ICAO is the Convention on International Civil Aviation, drawn up in Chicago in December 1944, and to which each ICAO Contracting State is a party. The principal body concerned with the development of technical Standards and other provisions is the Air Navigation Commission. Its primary role is to advise the Council of ICAO on air navigation issues. It is composed of fifteen experts with appropriate qualifications and experience in various fields of aviation. Its members are nominated by Contracting States and are appointed by the Council. They are expected to function as independent experts and not as representatives of their States.

Forms of Standards and Recommended Practices

Sixteen out of eighteen Annexes to the Convention are of a technical nature and therefore fall within the responsibilities of the Air Navigation Bureau and its sections. The remaining two Annexes, Facilitation and Security, are under the purview of the Air Transport Bureau. Since the majority of the Annexes concern technical issues, it is focused on them when the development process is described. ICAO standards and other provisions are developed in the following forms:

• Standards and Recommended Practices - collectively referred to as SARPs;
• Procedures for Air Navigation Services - called PANS;
• Regional Supplementary Procedures -referred to as SUPPs; and
• Guidance Material in several formats.

A Standard is defined as any specification for physical characteristics, configuration, material, performance, personnel or procedure, the uniform application of which is recognized as necessary for the safety or regularity of international air navigation and to which Contracting States will conform in accordance with the Convention; in the event of impossibility of compliance, notification to the Council is compulsory under Article 38 of the Convention.

A Recommended Practice is any specification for physical characteristics, configuration, material, performance, personnel or procedure, the uniform application of which is recognized as desirable in the interest of safety, regularity or efficiency of international air navigation, and to which Contracting States will endeavour to conform in accordance with the Convention. States are invited to inform the Council of non-compliance. SARPs are formulated in broad terms and restricted to essential requirements. For complex systems such as communications equipment, SARPs material is constructed in two sections: core SARPs material of a fundamental regulatory nature contained within the main body of the Annexes, and detailed technical specifications placed either in Appendices to Annexes or in manuals.

The differences to SARPS notified by States are published in Supplements to Annexes. Procedures for Air Navigation Services (or PANS) comprise operating practices and material too detailed for Standards or Recommended Practices -they often amplify the basic principles in the corresponding Standards and Recommended Practices. To qualify for PANS status, the material should be suitable for application on a worldwide basis. The Council invites Contracting States to publish any differences in their Aeronautical Information Publications when knowledge of the differences is important to the safety of air navigation. The provisions for Annex 18, Dangerous Goods, are supplemented by Technical Instructions for the Safe Transport of Dangerous Goods by Air. While these detailed instructions do not have the status of SARPs or PANS, they do have a special status by which the Contracting States are requested to achieve compliance. Regional Supplementary Procedures (or SUPPs) have application in the respective ICAO regions. Although the material in Regional Supplementary Procedures is similar to that in the Procedures for Air Navigation Services, SUPPs do not have the worldwide applicability of PANS. Guidance Material is produced to supplement the SARPs and PANS and to facilitate their implementation. Guidance material is issued as Attachments to Annexes or in separate documents such manuals, circulars and lists of designators/addresses. Usually it is approved at the same time as the related SARPS are adopted.

Manuals provide information to supplement and/or amplify the Standards and Recommended Practices and Procedures for Air Navigation Services. They are specifically designed to facilitate implementation and are amended periodically to ensure their contents reflect current practices and procedures. Circulars make available specialized information of interest to Contracting States. Unlike manuals, circulars are not normally updated.

The sections of the ICAO SARPS Annex 10 more related to SBAS standardisation are described next:

• CHAPTER 1 INTRODUCTION
• CHAPTER 2 GENERAL PROVISIONS FOR RADIO NAVIGATION AIDS
  • Section 2.4 “Global navigation satellite systems”
• CHAPTER 3 SPECIFICATIONS FOR RADIO NAVIGATION AIDS
  • Section 3.7 “Requirements for the Global Navigation Satellite System (GNSS)”
• Appendix B TECHNICAL SPECIFICATIONS FOR THE GLOBAL NAVIGATION SATELLITE SYSTEM
• SECTION 1: DEFINITION
• SECTION 2: GENERAL
• SECTION 3: GNSS ELEMENTS
  • SECTION 3.1: GLOBAL POSITIONING SYSTEM (GPS) STANDARD POSITIONINGSERVICE (SPS) (L1)
  • SECTION 3.2: GLOBAL NAVIGATION SATELLITE SYSTEM (GLONASS) CHANNELOF STANDARD ACCURACY (CSA) (L1)
  • SECTION 3.3: COMBINED USE OF GPS AND GLONASS
  • SECTION 3.4: AIRCRAFT-BASED AUGMENTATION SYSTEM (ABAS)
  • SECTION 3.5: SATELLITE-BASED AUGMENTATION SYSTEM (SBAS)
    • Section 3.5.1: General
    • Section 3.5.2: RF characteristics
    • Section 3.5.3: Data Structure
      • Section 3.5.3.1 Format summary
      • Section 3.5.3.2 Preamble
      • Section 3.5.3.3 Message type identifier
      • Section 3.5.3.4 Data Field
      • Section 3.5.3.5 Ciclic redundancy check (CRC)
    • Section 3.5.4: Data Content
      • Section 3.5.4.1 PRN mask parameters
      • Section 3.5.4.2 Geostationary orbit (GEO) ranging function parameters
      • Section 3.5.4.3 GEO almanac parameters
      • Section 3.5.4.4 Satellite correction broadcast parameters
      • Section 3.5.4.4.1 Long-term correction parameters
      • Section 3.5.4.4.2 Fast correction parameters
      • Section 3.5.4.5 Fast and long-term correction integrity parameters
      • Section 3.5.4.6 Ionospheric correction parameters
      • Section 3.5.4.7 Degradation parameterS-GMV-4100-O-021-U-V1.0 05/02/2008 17/34
      • Section 3.5.4.8 Time parameters
      • Section 3.5.4.9 Service region parameters
      • Section 3.5.4.10 Clock-ephemeris covariance matrix parameters
    • Section 3.5.5 Definitions of protocols for data application
      • Section 3.5.5.1 GEO position and clock
        • Section 3.5.5.1.1 GEO position estimation
        • Section 3.5.5.1.2 GEO clock correction
      • Section 3.5.5.2 Long-term corrections
        • Section 3.5.5.2.1 GPS clock correction
        • Section 3.5.5.2.2 GLONASS Clock correction
        • Section 3.5.5.2.3 Satellite position correction
      • Section 3.5.5.3 Pseudo-range corrections
      • Section 3.5.5.4 Range rate corrections (RRC).
      • Section 3.5.5.5 Broadcast ionospheric corrections
        • Section 3.5.5.5.1 Location of ionospheric pierce point (IPP)
        • Section 3.5.5.5.2 Ionospheric corrections
        • Section 3.5.5.5.3 Interpolated vertical ionospheric delay estimate
      • Section 3.5.5.6 Protection levels
    • Section 3.5.6 Message tables
    • Section 3.5.7 Non-aircraft elements
      • Section 3.5.7.1 General
      • Section 3.5.7.2 Ranging function
      • Section 3.5.7.3 GNSS satellite status function
      • Section 3.5.7.4 Basic differential correction function
      • Section 3.5.7.5 Precise differential correction function
      • Section 3.5.7.6 Optional functions
      • Section 3.5.7.7 Monitoring
    • Section 3.5.8 Aircraft elements
      • Section 3.5.8.1 SBAS-capable GNSS receiver
      • Section 3.5.8.2 RANGING FUNCTION
      • Section 3.5.8.3 GNSS satellite status function
      • Section 3.5.8.4 Basic and precise differential functions
    • Section 3.5.9 Interface between SBAS
  • SECTION 3.6: GROUND-BASED AUGMENTATION SYSTEM (GBAS)
  • SECTION 3.7 RESISTANCE TO INTERFERENCE
  • SECTION 3.8 GNSS AIRCRAFT SATELLITE RECEIVER ANTENNA
  • SECTION 3.9: CYCLIC REDUNDANCY CHECK

Credits

Except for updates and small modifications, the information presented in this article has been mostly extracted from chapter 1.8 of ESA SP-1303 book. The information therein was mainly obtained from the following homepages:

• ICAO website.
• EUROCAE website.
• ARINC website.
• JAA website.
• RTCA website.