Requirements

The satellite navigation aviation requirements were defined under the framework of ICAO, the International Civil Aviation Organisation. The Standards and Recommended Practices (SARPs) for GNSS were developed by the Global Navigation Satellite System Panel and feature in the ICAO document Convention on International Civil Aviation — Aeronautical Telecommunications, Annex 10, Volume 1 (Radio Navigation Aids), including Amendment 76. The guidance information and material in Attachment D to Annex 10 provides extensive guidance on the technical aspects and the application of GNSS SARPs.

The EGNOS system has been designed to enable safety critical civil aviation operations based on these SARPs criteria. The Accuracy, Integrity, Availability, Continuity requirements are listed in the table below.

In the early stages, EGNOS can support aviation navigation from En-Route down to the phase of flight “Approach with Vertical Guidance” APV I over the ECAC region. The level of performance corresponding to APV II is foreseen at the next stage, and Precision Approach CAT I can be reached once the dual frequency GPS+GALILEO+EGNOS combination of services are available. EGNOS can also support surface movement navigation.

In the USA, WAAS supports navigation down to the phases of flight Lateral Navigation and Vertical Navigation (LNAV/VNAV) and the Localizer Performance with Vertical guidance (LPV).

	Accuracy		Integrity				Availability	Continuity
	Lateral 95%	Vertical 95%	Alert Limit Lateral	Alert Limit Vertical	Integrity [1]	Time to Alert
En route	2.0 NM / 3704 m	N/A	4 NM / 7.4 km	N/A	1-10-7/h	5 min	0.99 to 0.99999	1-10-4/h to 1-10-8/h
En route, Continental	0.4 NM / 740 m	N/A	2 NM / 3.7 km	N/A	1-10-7/h	15 s	0.99 to 0.99999	1-10-4/h to 1-10-8/h
Terminal Area	0.4 NM / 740 m	N/A	1 NM / 1.85 km	N/A	1-10-7/h	15 s	0.999 to 0.99999	1-10-4/h to 1-10-8/h
Initial Approach, Departure	220 m	N/A	0.3 NM / 0.6 km	N/A	1-10-7/h	10 s	0.99 to 0.99999	1-10-4/h to 1-10-8/h
Non Precision Approach	220 m	N/A	1 NM / 1.85 km	NA	1-10-7/h	10 s	0.99 to 0.99999	1-10-4/h to 1-10-8/h
Approach Vertical Guidance APV I	16 m	20 m	40 m	50 m [2]	2-10-7 per approach [3]	10 s	0.99 to 0.99999	1-8x10-6 in any 15 s
Approach Vertical Guidance APV II	16 m	8 m	40 m	20 m	2-10-7 per approach [3]	6 s	0.99 to 0.99999	1-8x10-6 in any 15 s
Precision Approach CAT I	16 m	6 m to 4 m	40 m	12-10 m	2-10-7 per approach [3]	6 s	0.99 to 0.99999	1-8x10-6 in any 15 s

[1] Probability of HMI
[2] Not applicable to barometric VNAV
[3] Approach = 150 sec