The EGNOS SBAS Message Format Explained - Revision history

Natalia.Castrillo at 08:33, 25 February 2026

2026-02-25T08:33:52Z

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	This message contains the navigation data (as Keplerian parameters) describing the coarse position of two SBAS broadcasting satellites (for any type of orbit).		This message contains the navigation data (as Keplerian parameters) describing the coarse position of two SBAS broadcasting satellites (for any type of orbit).

	==~~Files format~~ for embedding SBAS messages==		==File formats for embedding SBAS messages==
	~~SBAS messages are typically embedded in EMS files~~ (EGNOS Message Server).		For offline analysis and non-SoL/non-real-time applications, familiarization with EGNOS system or general research, the European Space Agency (ESA) has developed the EGNOS Message Server (EMS) file format. EMS is a well-known file format that captures, per GEO satellite and epoch, the Navigation Overlay Frames (NOF) broadcast to single-frequency L1 users. EMS file format is not limited to EGNOS but can contain NOF from any RTCA MOPS DO-229 compliant SBAS.
			The format definition of EGNOS legacy service (SF) is available here: [[:File:EMS_UID_2_0.pdf\|EMS_UID_2_0.pdf]].

	~~The format definition for~~ EGNOS ~~legacy service~~ (SF) ~~is available here: [[:~~File~~:EMS_UID_2_0.pdf\|EMS_UID_2_0~~.~~pdf]]~~		In future major system upgrades (V3.x), EGNOS will also provide information to dual-frequency and multi-constellation (DFMC) users (more specifically, receivers using both L1/E1 and L5/E5a frequencies of GPS and Galileo). To support this evolution, new standards such as the DFMC SBAS MOPS and message formats (such as this Multi-Band EGNOS File Format) have been created to serve a larger user community and benefit from increased processing on user side.
			The new Multi-Band EGNOS File Format is backwards compatible with the legacy EMS format and is available here: [[:File:EMS_UID_Multi-band.pdf\|EMS_UID_Multi-band.pdf]].
	A new ~~format (~~backwards compatible) is ~~EMS Multi-band to also embed messages for new SBAS services (including DFMC)~~: [[:File:EMS_UID_Multi-band.pdf\|EMS_UID_Multi-band.pdf]]

	==Summary==		==Summary==
	The aim of this article is to provide a ~~résumé~~ of what the structure of the signal broadcast by EGNOS is, based on the Appendix A of the RTCA MOPS DO-229-C and the Appendix B of the ICAO SARPs. It goes towards those readers not familiarised with aviation equipment standards, especially with MOPS and SARPs.		The aim of this article is to provide a summary of what the structure of the signal broadcast by EGNOS is, based on the Appendix A of the RTCA MOPS DO-229-C and the Appendix B of the ICAO SARPs. It goes towards those readers not familiarised with aviation equipment standards, especially with MOPS and SARPs.

	It presents the data that are broadcast by EGNOS through the GEO satellites and how this information is distributed in their signals. In addition to the GEO L1 ranging signal (GPS-like), EGNOS broadcasts differential corrections, ionospheric delay estimations for a set of predefined points defined on a grid 350km above the WGS-84 ellipsoid Earth approximation (IGPs), and integrity information to inform about the goodness of the service provided. A model to obtain the tropospheric delays is used instead of any kind of broadcast data due to the local character of the troposphere.		It presents the data that are broadcast by EGNOS through the GEO satellites and how this information is distributed in their signals. In addition to the GEO L1 ranging signal (GPS-like), EGNOS broadcasts differential corrections, ionospheric delay estimations for a set of predefined points defined on a grid 350km above the WGS-84 ellipsoid Earth approximation (IGPs), and integrity information to inform about the goodness of the service provided. A model to obtain the tropospheric delays is used instead of any kind of broadcast data due to the local character of the troposphere.

Pierre.Lesage: Addition of File Format description for EMS files in a new section (Files format for embedding SBAS messages)

2026-02-24T16:33:28Z

Addition of File Format description for EMS files in a new section (Files format for embedding SBAS messages)

← Older revision		Revision as of 16:33, 24 February 2026
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	==Files format for embedding SBAS messages==		==Files format for embedding SBAS messages==
	SBAS messages are typically embedded in EMS files (EGNOS Message Server).		SBAS messages are typically embedded in EMS files (EGNOS Message Server).
	The format definition ~~for this file~~ for EGNOS legacy service (SF) is available here: [[:File:EMS_UID_2_0.pdf\|EMS_UID_2_0.pdf]]
			The format definition for EGNOS legacy service (SF) is available here: [[:File:EMS_UID_2_0.pdf\|EMS_UID_2_0.pdf]]

			A new format (backwards compatible) is EMS Multi-band to also embed messages for new SBAS services (including DFMC): [[:File:EMS_UID_Multi-band.pdf\|EMS_UID_Multi-band.pdf]]

	==Summary==		==Summary==

Pierre.Lesage: Addition of EGNOS EMS File ICD

2026-02-24T16:26:16Z

Addition of EGNOS EMS File ICD

← Older revision		Revision as of 16:26, 24 February 2026
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	====Message Type 47: SBAS satellite almanacs====		====Message Type 47: SBAS satellite almanacs====
	This message contains the navigation data (as Keplerian parameters) describing the coarse position of two SBAS broadcasting satellites (for any type of orbit).		This message contains the navigation data (as Keplerian parameters) describing the coarse position of two SBAS broadcasting satellites (for any type of orbit).

			==Files format for embedding SBAS messages==
			SBAS messages are typically embedded in EMS files (EGNOS Message Server).
			The format definition for this file for EGNOS legacy service (SF) is available here: [[:File:EMS_UID_2_0.pdf\|EMS_UID_2_0.pdf]]

	==Summary==		==Summary==

Gema.Cueto at 07:35, 29 November 2018

2018-11-29T07:35:25Z

← Older revision		Revision as of 07:35, 29 November 2018
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	===SBAS L5 Messages===		===SBAS L5 Messages===
	The proposed L5 MOPS ephemeris message is based on an augmented set of Keplerian orbital elements. Like its predecessor, it remains a 9 degree of freedom parameterization of the orbit and is based on a subset of the GPS ephemeris orbital elements. The message parameters are given below. It consists of a nominal elliptical trajectory described by the six Keplerian elements as well as an additional three correction terms, namely, a correction rate in the inclination IDOT, as well as the so-called harmonic correction terms in the along-track direction Cus and Cuc, which allow us to achieve the necessary orbit representation accuracy. The rate in the inclination allows for cross track correction and the harmonic correction terms, which are a subset of those employed by the GPS ephemeris, allow for along-track correction due to J2 effects. It was determined that over the time scale of this message the dominant 3D position errors observed in using the six Keplerian elements were in the transverse direction, not radial. To mitigate this, we selected parameters which allowed for additional corrections in the along- and cross-track directions.~~</ref><ref name=" L5 MOPS">[https://www.researchgate.net/publication/269338469_Qualifying_an_L5_SBAS_MOPS_ephemeris_message_to_support_multiple_orbit_classes]</ref>~~		The proposed L5 MOPS ephemeris message is based on an augmented set of Keplerian orbital elements. Like its predecessor, it remains a 9 degree of freedom parameterization of the orbit and is based on a subset of the GPS ephemeris orbital elements. The message parameters are given below. It consists of a nominal elliptical trajectory described by the six Keplerian elements as well as an additional three correction terms, namely, a correction rate in the inclination IDOT, as well as the so-called harmonic correction terms in the along-track direction Cus and Cuc, which allow us to achieve the necessary orbit representation accuracy. The rate in the inclination allows for cross track correction and the harmonic correction terms, which are a subset of those employed by the GPS ephemeris, allow for along-track correction due to J2 effects. It was determined that over the time scale of this message the dominant 3D position errors observed in using the six Keplerian elements were in the transverse direction, not radial. To mitigate this, we selected parameters which allowed for additional corrections in the along- and cross-track directions.

Gema.Cueto at 07:34, 29 November 2018

2018-11-29T07:34:29Z

← Older revision		Revision as of 07:34, 29 November 2018
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	===SBAS L5 Messages===		===SBAS L5 Messages===
			The proposed L5 MOPS ephemeris message is based on an augmented set of Keplerian orbital elements. Like its predecessor, it remains a 9 degree of freedom parameterization of the orbit and is based on a subset of the GPS ephemeris orbital elements. The message parameters are given below. It consists of a nominal elliptical trajectory described by the six Keplerian elements as well as an additional three correction terms, namely, a correction rate in the inclination IDOT, as well as the so-called harmonic correction terms in the along-track direction Cus and Cuc, which allow us to achieve the necessary orbit representation accuracy. The rate in the inclination allows for cross track correction and the harmonic correction terms, which are a subset of those employed by the GPS ephemeris, allow for along-track correction due to J2 effects. It was determined that over the time scale of this message the dominant 3D position errors observed in using the six Keplerian elements were in the transverse direction, not radial. To mitigate this, we selected parameters which allowed for additional corrections in the along- and cross-track directions.</ref><ref name=" L5 MOPS">[https://www.researchgate.net/publication/269338469_Qualifying_an_L5_SBAS_MOPS_ephemeris_message_to_support_multiple_orbit_classes]</ref>



	{\|{{Prettytable}}		{\|{{Prettytable}}
	\|+ align="bottom"\|'''''Table 8:''''' SBAS L5 Message types.		\|+ align="bottom"\|'''''Table 8:''''' SBAS L5 Message types.

Gema.Cueto at 11:27, 19 November 2018

2018-11-19T11:27:09Z

Show changes

Teresa.Ferreira at 09:25, 22 February 2013

2013-02-22T09:25:26Z

← Older revision		Revision as of 09:25, 22 February 2013
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	====Message type 1====		====Message type 1====
	Message type 1 includes the PRN mask assignments, chosen among ~~GPS, GLONASS~~ and GEO satellites. Instead of sending for each correction the satellite PRN associated with, a mask is created to save space in the messages. This bit mask contains the i-th bit to 1 to inform that i-th satellite PRN is being used.		Message type 1 includes the PRN mask assignments, chosen among the applicable GNSS and GEO satellites. Instead of sending for each correction the satellite PRN associated with, a mask is created to save space in the messages. This bit mask contains the i-th bit to 1 to inform that i-th satellite PRN is being used.

	Although there are 210 slots (bits) in the mask, only a maximum of 51 can be set at a time due to constraint in the limited size available to broadcast information (message type 6 does only have enough free space to allocate UDREI figures for 51 satellites). Corrections are provided only for these satellites.		Although there are 210 slots (bits) in the mask, only a maximum of 51 can be set at a time due to constraint in the limited size available to broadcast information (message type 6 does only have enough free space to allocate UDREI figures for 51 satellites). Corrections are provided only for these satellites.
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	====Message type 9====		====Message type 9====
	Message type 9 contains the information about the GEO navigation.		Message type 9 contains the information about the GEO navigation.
	As GEO satellites do not belong to any satellite positioning service (GPS, GLONASS), ephemeris for those satellites are not externally available. Therefore, it is the SBAS that is in charge of providing the user with the GEO ephemeris. Keep in mind that all components are expressed in ECEF reference coordinates and the time offset is with respect to SBAS Network time (SNT).		As GEO satellites do not belong to any satellite positioning service (e.g. GPS, GLONASS), ephemeris for those satellites are not externally available. Therefore, it is the SBAS that is in charge of providing the user with the GEO ephemeris. Keep in mind that all components are expressed in ECEF reference coordinates and the time offset is with respect to SBAS Network time (SNT).

	The message format is included in the section A.4.4.11 of MOPS. In addition to the ephemeris data an URA (User Range Accuracy), as defined for GPS satellites, is also provided. An IODN used to link the GEO long-term corrections with the message type 9 ephemeris is included in the previous versions of MOPS, but it has been removed from MOPS. However EGNOS makes use of this parameter to match the long-term corrections broadcast for its GEO satellites with the appropriate navigation data broadcast through message type 9.		The message format is included in the section A.4.4.11 of MOPS. In addition to the ephemeris data an URA (User Range Accuracy), as defined for GPS satellites, is also provided. An IODN used to link the GEO long-term corrections with the message type 9 ephemeris is included in the previous versions of MOPS, but it has been removed from MOPS. However EGNOS makes use of this parameter to match the long-term corrections broadcast for its GEO satellites with the appropriate navigation data broadcast through message type 9.
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	Message type 25 includes estimations of slow varying satellite ephemeris and clock errors (in ECEF WGS-84) with respect to the ephemeris and clock parameters broadcast by the satellite navigation service. IODE is used to relate the long-term corrections with the ephemeris used to which the corrections are computed.		Message type 25 includes estimations of slow varying satellite ephemeris and clock errors (in ECEF WGS-84) with respect to the ephemeris and clock parameters broadcast by the satellite navigation service. IODE is used to relate the long-term corrections with the ephemeris used to which the corrections are computed.

	~~The satellites for which these long~~-term corrections are available ~~are:~~		Long-term corrections are available to both the applicable GNSS and GEO satellites that belong to another SBAS.
	* GPS satellites
	* GLONASS satellites
	* GEO satellites that belong to another SBAS

	Long-term corrections for GEO satellites that do belong to the SBAS will be included in message type 9. Note however that this is not EGNOS approach. In addition to this, for visible GEO satellites not belonging to the SBAS but providing long-term corrections in message type 25, these corrections in message type 25 have to be related with message type 9 coming from the other SBAS. EGNOS makes use of satellite IODN of message type 9 although this parameter has been removed from MOPS and SARPS.		Long-term corrections for GEO satellites that do belong to the SBAS will be included in message type 9. Note however that this is not EGNOS approach. In addition to this, for visible GEO satellites not belonging to the SBAS but providing long-term corrections in message type 25, these corrections in message type 25 have to be related with message type 9 coming from the other SBAS. EGNOS makes use of satellite IODN of message type 9 although this parameter has been removed from MOPS and SARPS.
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	The aim of this article is to provide a résumé of what the structure of the signal broadcast by EGNOS is, based on the Appendix A of the RTCA MOPS DO-229-C and the Appendix B of the ICAO SARPs. It goes towards those readers not familiarised with aviation equipment standards, especially with MOPS and SARPs.		The aim of this article is to provide a résumé of what the structure of the signal broadcast by EGNOS is, based on the Appendix A of the RTCA MOPS DO-229-C and the Appendix B of the ICAO SARPs. It goes towards those readers not familiarised with aviation equipment standards, especially with MOPS and SARPs.

	It presents the data that are broadcast by EGNOS through the GEO satellites and how this information is distributed in their signals. In addition to the GEO L1 ranging signal (GPS-like), EGNOS ~~does broadcast~~ differential corrections ~~for GPS/GLONASS/GEO~~, ionospheric delay estimations for a set of predefined points defined on a grid 350km above the WGS-84 ellipsoid Earth approximation (IGPs), and integrity information to inform about the goodness of the service provided. A model to obtain the tropospheric delays is used instead of any kind of broadcast data due to the local character of the troposphere.		It presents the data that are broadcast by EGNOS through the GEO satellites and how this information is distributed in their signals. In addition to the GEO L1 ranging signal (GPS-like), EGNOS broadcasts differential corrections, ionospheric delay estimations for a set of predefined points defined on a grid 350km above the WGS-84 ellipsoid Earth approximation (IGPs), and integrity information to inform about the goodness of the service provided. A model to obtain the tropospheric delays is used instead of any kind of broadcast data due to the local character of the troposphere.

	EGNOS does provide all this information through messages (blocks of 250 bits) encoded in the GEO signal. These messages are composed of a preamble, a type identifier, the message body and finally CRC parity information. The maximum update intervals for the data contained in the different messages are predefined and EGNOS Service Provider accounts for them for transmitting all the information in due time.		EGNOS does provide all this information through messages (blocks of 250 bits) encoded in the GEO signal. These messages are composed of a preamble, a type identifier, the message body and finally CRC parity information. The maximum update intervals for the data contained in the different messages are predefined and EGNOS Service Provider accounts for them for transmitting all the information in due time.

Teresa.Ferreira at 09:20, 22 February 2013

2013-02-22T09:20:39Z

← Older revision		Revision as of 09:20, 22 February 2013
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	This article contains a brief summary of EGNOS signal structure as described in RTCA MOPS DO-229-C “''Minimum Operational Performance Standards for Global Positioning System/Wide Area Augmentation System airborne equipment''” (particularly in its Appendix A “''Signal characteristics and format''”) just to allow the reader to have a first contact with the specification of the SiS that is applicable for Satellite Based Augmentation Systems (SBAS), in particular for the European EGNOS.		This article contains a brief summary of EGNOS signal structure as described in RTCA MOPS DO-229-C “''Minimum Operational Performance Standards for Global Positioning System/Wide Area Augmentation System airborne equipment''” (particularly in its Appendix A “''Signal characteristics and format''”) just to allow the reader to have a first contact with the specification of the SiS that is applicable for Satellite Based Augmentation Systems (SBAS), in particular for the European EGNOS.

	It is worthwhile to highlight that the SBAS SiS specification is also detailed in the ICAO SARPs “Standards and Recommended Practices”, Appendix B “Detailed technical specifications for the Global Navigation Satellite System (GNSS)”. These two standards are nearly aligned in what regards to the SBAS SiS specification but still some differences remain. In fact, some topics such as the augmentation of GLONASS constellation is covered by the ICAO SARPs but not by the MOPS ~~(WAAS does not provides augmentation to GLONASS satellites)~~ and hence both MOPS and SARPs will be referenced along the following paragraphs.		It is worthwhile to highlight that the SBAS SiS specification is also detailed in the ICAO SARPs “Standards and Recommended Practices”, Appendix B “Detailed technical specifications for the Global Navigation Satellite System (GNSS)”. These two standards are nearly aligned in what regards to the SBAS SiS specification but still some differences remain. In fact, some topics such as the augmentation of GLONASS constellation is covered by the ICAO SARPs but not by the MOPS and hence both MOPS and SARPs will be referenced along the following paragraphs.

	For a more precise knowledge of EGNOS SiS specification the reading of the aforementioned annex of MOPS is recommended. The purpose of the material presented hereafter is just to summarise the contents of MOPS Appendix A in order to make easier the first touch with it for those readers that are not familiarised with aviation equipment standards.		For a more precise knowledge of EGNOS SiS specification the reading of the aforementioned annex of MOPS is recommended. The purpose of the material presented hereafter is just to summarise the contents of MOPS Appendix A in order to make easier the first touch with it for those readers that are not familiarised with aviation equipment standards.
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	Every satellite-based wide area augmentation system, as the European system EGNOS, does provide ranging signals transmitted by GEO satellites, differential corrections on the wide area and additional parameters aimed to guarantee the integrity of the GNSS user:		Every satellite-based wide area augmentation system, as the European system EGNOS, does provide ranging signals transmitted by GEO satellites, differential corrections on the wide area and additional parameters aimed to guarantee the integrity of the GNSS user:
	* GEO Ranging: transmission of GPS-like L1 signals from GEO satellites to augment the number of navigation satellites available to the users.		* GEO Ranging: transmission of GPS-like L1 signals from GEO satellites to augment the number of navigation satellites available to the users.
	* Wide Area Differential (WAD): differential corrections to the ~~existing GPS/GLONASS~~/GEO navigation services computed in a wide area to improve navigation services performance.		* Wide Area Differential (WAD): differential corrections to the applicable GNSS/GEO navigation services computed in a wide area to improve navigation services performance.
	* GNSS/Ground Integrity Channel (GIC): integrity information to inform about the availability of ~~GPS/GLONASS~~/GEO safe navigation service.		* GNSS/Ground Integrity Channel (GIC): integrity information to inform about the availability of GNSS/GEO safe navigation service.
	SBAS shall provide the following information:		SBAS shall provide the following information:
	* Satellite orbit and clock corrections to the existing satellite navigation services (~~GPS, GLONASS~~ and GEO), as well as the estimation of errors associated to satellites (UDRE).		* Satellite orbit and clock corrections to the existing satellite navigation services (GNSS and GEO), as well as the estimation of errors associated to satellites (UDRE).
	* Ionospheric corrections for a given grid of points, as well as the estimation of errors associated to ionosphere (GIVE).		* Ionospheric corrections for a given grid of points, as well as the estimation of errors associated to ionosphere (GIVE).
	* Tropospheric corrections. Satellite orbit/clock corrections and ionospheric corrections are dynamically modelled. The SBAS shall communicate the user the corrections that are available to be used by the receiver. The information of the models is packed on messages to be sent to the user. On the other hand, tropospheric corrections are statically modelled, which means that corrections are tabulated and the information does not depend on any external behaviour but the user position (a mean troposphere is assumed). The algorithm for computing the tropospheric correction is available to the global community (section A.4.2.4 of MOPS).		* Tropospheric corrections. Satellite orbit/clock corrections and ionospheric corrections are dynamically modelled. The SBAS shall communicate the user the corrections that are available to be used by the receiver. The information of the models is packed on messages to be sent to the user. On the other hand, tropospheric corrections are statically modelled, which means that corrections are tabulated and the information does not depend on any external behaviour but the user position (a mean troposphere is assumed). The algorithm for computing the tropospheric correction is available to the global community (section A.4.2.4 of MOPS).

Teresa.Ferreira: /* Introduction */

2013-02-22T09:18:04Z

Introduction

← Older revision		Revision as of 09:18, 22 February 2013
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	This article contains a brief summary of EGNOS signal structure as described in RTCA MOPS DO-229-C “''Minimum Operational Performance Standards for Global Positioning System/Wide Area Augmentation System airborne equipment''” (particularly in its Appendix A “''Signal characteristics and format''”) just to allow the reader to have a first contact with the specification of the SiS that is applicable for Satellite Based Augmentation Systems (SBAS), in particular for the European EGNOS.		This article contains a brief summary of EGNOS signal structure as described in RTCA MOPS DO-229-C “''Minimum Operational Performance Standards for Global Positioning System/Wide Area Augmentation System airborne equipment''” (particularly in its Appendix A “''Signal characteristics and format''”) just to allow the reader to have a first contact with the specification of the SiS that is applicable for Satellite Based Augmentation Systems (SBAS), in particular for the European EGNOS.

	It is worthwhile to highlight that the SBAS SiS specification is also detailed in the ICAO SARPs “Standards and Recommended Practices”, Appendix B “Detailed technical specifications for the Global Navigation Satellite System (GNSS)”. These two standards are nearly aligned in what regards to the SBAS SiS specification but still some differences remain. In fact, some topics such as the augmentation of GLONASS constellation ~~by EGNOS~~ is covered by the ICAO SARPs but not by the MOPS (WAAS does not provides augmentation to GLONASS satellites) and hence both MOPS and SARPs will be referenced along the following paragraphs.		It is worthwhile to highlight that the SBAS SiS specification is also detailed in the ICAO SARPs “Standards and Recommended Practices”, Appendix B “Detailed technical specifications for the Global Navigation Satellite System (GNSS)”. These two standards are nearly aligned in what regards to the SBAS SiS specification but still some differences remain. In fact, some topics such as the augmentation of GLONASS constellation is covered by the ICAO SARPs but not by the MOPS (WAAS does not provides augmentation to GLONASS satellites) and hence both MOPS and SARPs will be referenced along the following paragraphs.

	For a more precise knowledge of EGNOS SiS specification the reading of the aforementioned annex of MOPS is recommended. The purpose of the material presented hereafter is just to summarise the contents of MOPS Appendix A in order to make easier the first touch with it for those readers that are not familiarised with aviation equipment standards.		For a more precise knowledge of EGNOS SiS specification the reading of the aforementioned annex of MOPS is recommended. The purpose of the material presented hereafter is just to summarise the contents of MOPS Appendix A in order to make easier the first touch with it for those readers that are not familiarised with aviation equipment standards.

Carlos.Lopez at 11:12, 23 February 2012

2012-02-23T11:12:12Z

← Older revision		Revision as of 11:12, 23 February 2012
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	{{Article Infobox2		{{Article Infobox2
	\|Category=EGNOS		\|Category=EGNOS
	~~\|Title={{PAGENAME}}~~
	\|Authors=Daniel Porras Sánchez & César Pisonero Berges, GMV S.A., Spain.		\|Authors=Daniel Porras Sánchez & César Pisonero Berges, GMV S.A., Spain.
	~~\|Logo=ESA~~
	\|Level=Basic		\|Level=Basic
	\|YearOfPublication=2006		\|YearOfPublication=2006
			\|Logo=ESA
			\|Title={{PAGENAME}}
	}}		}}
	==Introduction==		==Introduction==