Criticality of GNSS Applications - Revision history

Filipe.Pelica: Included editor logo.

2014-09-18T15:17:37Z

Included editor logo.

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Carlos.Lopez at 10:50, 23 February 2012

2012-02-23T10:50:26Z

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Carlos.Lopez at 10:39, 23 February 2012

2012-02-23T10:39:46Z

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	GNSS systems can serve to many different purposes or applications, with different tolerances to system failures or errors. Attending to the criticality that an unwarned error or failure of the GNSS system has for a particular application, these will be classified in different categories.		GNSS systems can serve to many different purposes or applications, with different tolerances to system failures or errors. Attending to the criticality that an unwarned error or failure of the GNSS system has for a particular application, these will be classified in different categories.

Timo.Kouwenhoven: Text replace - "|Level=Medium" to "|Level=Intermediate"

2011-11-06T07:41:14Z

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Timo.Kouwenhoven: /* Categorization of the Criticality of GNSS Applications */

2011-03-21T15:17:11Z

Categorization of the Criticality of GNSS Applications

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	== Categorization of the Criticality of GNSS Applications ==		== Categorization of the Criticality of GNSS Applications ==
	In terms of criticality the GNSS Applications can be classified in three different groups:		In terms of criticality the GNSS Applications can be classified in three different groups:
	*Safety Critical applications (SCA)		# Safety Critical applications (SCA)
	*Liability Critical applications (LCA)		# Liability Critical applications (LCA)
	*Non-Critical applications (NCA)		# Non-Critical applications (NCA)

	===Safety Critical Applications===		===Safety Critical Applications===

Timo.Kouwenhoven: /* Categorization of the Criticality of GNSS Applications */

2011-03-21T15:16:37Z

Categorization of the Criticality of GNSS Applications

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	*Liability Critical applications (LCA)		*Liability Critical applications (LCA)
	*Non-Critical applications (NCA)		*Non-Critical applications (NCA)


	===Safety Critical Applications===		===Safety Critical Applications===

Timo.Kouwenhoven: /* Categorization of the Criticality of GNSS Applications */

2011-03-21T15:16:19Z

Categorization of the Criticality of GNSS Applications

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	Safety Critical Applications are not only those that a misbehavior can cause deaths and accidents, but also some other application that are prone to produce a reduction in the number or people injured or killed (as it is the case of emergency services, traffic information in real time, and so on). Both types have been considered under Safety Critical Application group.		Safety Critical Applications are not only those that a misbehavior can cause deaths and accidents, but also some other application that are prone to produce a reduction in the number or people injured or killed (as it is the case of emergency services, traffic information in real time, and so on). Both types have been considered under Safety Critical Application group.

	:Examples of Safety Critical Applications include air and maritime navigation or advanced driving assistance systems (ADAS).		====Examples====
			Examples of Safety Critical Applications include:
			* air and maritime navigation or
			* advanced driving assistance systems (ADAS).

	===Liability Critical Applications===		===Liability Critical Applications===
	Liability Critical Applications are those where the consequences on navigation of undetected GNSS miss-performances can generate significant legal or economic consequences<ref>[http://www.oosa.unvienna.org/pdf/icg/2010/workgroupb1/03.pdf Interoperability for Liability Critical Applications], M. Azaola (GMV), International GNSS Committee, Working Group B, Special Meeting on GNSS User Positioning Integrity, Munich, 2010</ref><ref>Integrity in urban and road environments and its use in liability critical applications, J Cosmen-Schortmann, M A Martinez-Olagüe, M Azaola-Saenz, M Toledo-Lopez, Position Location and Navigation Symposium 2008 IEEEION (2008) </ref>.		Liability Critical Applications are those where the consequences on navigation of undetected GNSS miss-performances can generate significant legal or economic consequences<ref>[http://www.oosa.unvienna.org/pdf/icg/2010/workgroupb1/03.pdf Interoperability for Liability Critical Applications], M. Azaola (GMV), International GNSS Committee, Working Group B, Special Meeting on GNSS User Positioning Integrity, Munich, 2010</ref><ref>Integrity in urban and road environments and its use in liability critical applications, J Cosmen-Schortmann, M A Martinez-Olagüe, M Azaola-Saenz, M Toledo-Lopez, Position Location and Navigation Symposium 2008 IEEEION (2008) </ref>.

	:Examples of Liability Critical Applications are road tolling, traffic law enforcement, Pay-As-You-Drive (PAYD) insurance, On-street parking pricing, Surveillance of Parolees and Fleet management (special vehicle classes).		====Examples====
			Examples of Liability Critical Applications are
			* road tolling,
			* traffic law enforcement,
			* Pay-As-You-Drive (PAYD) insurance,
			* On-street parking pricing,
			* Surveillance of Parolees and
			* Fleet management (special vehicle classes).

	===Non-Critical Applications===		===Non-Critical Applications===
	Non-Critical Applications are all applications not presenting any commercial, legal or safety implications. Due to these reasons, the technological requirements are, in general, more relaxed than the ones needed in previous application groups.		Non-Critical Applications are all applications not presenting any commercial, legal or safety implications. Due to these reasons, the technological requirements are, in general, more relaxed than the ones needed in previous application groups.

	:Most common uses of GNSS navigation devices, such as searching for nearby facilities (gas stations, restaurants, etc.) do not involve legal, economic or health risks, and hence are Non-Critical Applications.		Most common uses of GNSS navigation devices, such as searching for nearby facilities (gas stations, restaurants, etc.) do not involve legal, economic or health risks, and hence are Non-Critical Applications.

	== Main Features of LCA and Comparison with SCA ==		== Main Features of LCA and Comparison with SCA ==

Timo.Kouwenhoven at 15:06, 21 March 2011

2011-03-21T15:06:15Z

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	GNSS systems can serve to many different purposes or applications, with different tolerances to system failures or errors. Attending to the criticality that an unwarned error or failure of the GNSS system has for a particular application, these will be classified in different categories.		GNSS systems can serve to many different purposes or applications, with different tolerances to system failures or errors. Attending to the criticality that an unwarned error or failure of the GNSS system has for a particular application, these will be classified in different categories.


	== Categorization of the Criticality of GNSS Applications ==		== Categorization of the Criticality of GNSS Applications ==


	In terms of criticality the GNSS Applications can be classified in three different groups:		In terms of criticality the GNSS Applications can be classified in three different groups:
	*Safety Critical applications (SCA)		*Safety Critical applications (SCA)
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	~~'''~~Safety Critical Applications~~'''~~		===Safety Critical Applications===
			Safety Critical Applications are those that possess the potential of directly or indirectly causing harm to humans, destruction of the system, damage to property external to the system, or damage to the environment.<ref> [http://www.system-safety.org/Documents/NASA-STD-8719.13B.pdf NASA Software Safety Standard NASA-STD-8719.13B w/Change 1], July 8, 2004</ref>. All applications considered as safety critical, or having any safety implication, although indirect, are considered under this group.
	:Safety Critical Applications are those that possess the potential of directly or indirectly causing harm to humans, destruction of the system, damage to property external to the system, or damage to the environment.<ref> [http://www.system-safety.org/Documents/NASA-STD-8719.13B.pdf NASA Software Safety Standard NASA-STD-8719.13B w/Change 1], July 8, 2004</ref>. All applications considered as safety critical, or having any safety implication, although indirect, are considered under this group.
	:Safety Critical Applications are not only those that a misbehavior can cause deaths and accidents, but also some other application that are prone to produce a reduction in the number or people injured or killed (as it is the case of emergency services, traffic information in real time, and so on). Both types have been considered under Safety Critical Application group.		Safety Critical Applications are not only those that a misbehavior can cause deaths and accidents, but also some other application that are prone to produce a reduction in the number or people injured or killed (as it is the case of emergency services, traffic information in real time, and so on). Both types have been considered under Safety Critical Application group.

	:Examples of Safety Critical Applications include air and maritime navigation or advanced driving assistance systems (ADAS).		:Examples of Safety Critical Applications include air and maritime navigation or advanced driving assistance systems (ADAS).

			===Liability Critical Applications===
	~~'''~~Liability Critical ~~applications'''~~		Liability Critical Applications are those where the consequences on navigation of undetected GNSS miss-performances can generate significant legal or economic consequences<ref>[http://www.oosa.unvienna.org/pdf/icg/2010/workgroupb1/03.pdf Interoperability for Liability Critical Applications], M. Azaola (GMV), International GNSS Committee, Working Group B, Special Meeting on GNSS User Positioning Integrity, Munich, 2010</ref><ref>Integrity in urban and road environments and its use in liability critical applications, J Cosmen-Schortmann, M A Martinez-Olagüe, M Azaola-Saenz, M Toledo-Lopez, Position Location and Navigation Symposium 2008 IEEEION (2008) </ref>.

	:Liability Critical Applications are those where the consequences on navigation of undetected GNSS miss-performances can generate significant legal or economic consequences<ref>[http://www.oosa.unvienna.org/pdf/icg/2010/workgroupb1/03.pdf Interoperability for Liability Critical Applications], M. Azaola (GMV), International GNSS Committee, Working Group B, Special Meeting on GNSS User Positioning Integrity, Munich, 2010</ref><ref>Integrity in urban and road environments and its use in liability critical applications, J Cosmen-Schortmann, M A Martinez-Olagüe, M Azaola-Saenz, M Toledo-Lopez, Position Location and Navigation Symposium 2008 IEEEION (2008) </ref>.

	:Examples of Liability Critical Applications are road tolling, traffic law enforcement, Pay-As-You-Drive (PAYD) insurance, On-street parking pricing, Surveillance of Parolees and Fleet management (special vehicle classes).		:Examples of Liability Critical Applications are road tolling, traffic law enforcement, Pay-As-You-Drive (PAYD) insurance, On-street parking pricing, Surveillance of Parolees and Fleet management (special vehicle classes).

			===Non-Critical Applications===
	~~'''~~Non-Critical Applications~~'''~~		Non-Critical Applications are all applications not presenting any commercial, legal or safety implications. Due to these reasons, the technological requirements are, in general, more relaxed than the ones needed in previous application groups.

	:Non-Critical Applications are all applications not presenting any commercial, legal or safety implications. Due to these reasons, the technological requirements are, in general, more relaxed than the ones needed in previous application groups.

	:Most common uses of GNSS navigation devices, such as searching for nearby facilities (gas stations, restaurants, etc.) do not involve legal, economic or health risks, and hence are Non-Critical Applications.		:Most common uses of GNSS navigation devices, such as searching for nearby facilities (gas stations, restaurants, etc.) do not involve legal, economic or health risks, and hence are Non-Critical Applications.


	== Main Features of LCA and Comparison with SCA ==		== Main Features of LCA and Comparison with SCA ==


	Going through a bottom-up revision of LCA and their common points and differences with SCA, the four main performance parameters are going to be analyzed in terms of their impact in LCA and SCA.		Going through a bottom-up revision of LCA and their common points and differences with SCA, the four main performance parameters are going to be analyzed in terms of their impact in LCA and SCA.

Rui.Pereira at 14:35, 17 March 2011

2011-03-17T14:35:45Z

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	Going through a bottom-up revision of LCA and their common points and differences with SCA, the four main performance parameters are going to analyzed in terms of their impact in LCA and SCA.		Going through a bottom-up revision of LCA and their common points and differences with SCA, the four main performance parameters are going to be analyzed in terms of their impact in LCA and SCA.

Rui.Pereira at 14:32, 17 March 2011

2011-03-17T14:32:19Z

← Older revision		Revision as of 14:32, 17 March 2011
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	~~Positioning~~ systems can serve to many different purposes or applications, with different tolerances to system failures or errors. Attending to the criticality that an unwarned error or failure of the ~~positioning~~ system has for a particular application, these will be classified in different categories.		GNSS systems can serve to many different purposes or applications, with different tolerances to system failures or errors. Attending to the criticality that an unwarned error or failure of the GNSS system has for a particular application, these will be classified in different categories.


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	'''Liability Critical applications'''		'''Liability Critical applications'''

	:Liability Critical Applications are those where the consequences on navigation of undetected GNSS miss-performances can generate significant legal or economic consequences<ref>[http://www.oosa.unvienna.org/pdf/icg/2010/workgroupb1/03.pdf Interoperability for Liability Critical Applications], M. Azaola (GMV), International GNSS Committee, Working Group B, ~~Spetial~~ Meeting on GNSS User Positioning Integrity, Munich, 2010</ref><ref>Integrity in urban and road environments and its use in liability critical applications, J Cosmen-Schortmann, M A Martinez-Olagüe, M Azaola-Saenz, M Toledo-Lopez, Position Location and Navigation Symposium 2008 IEEEION (2008) </ref>.		:Liability Critical Applications are those where the consequences on navigation of undetected GNSS miss-performances can generate significant legal or economic consequences<ref>[http://www.oosa.unvienna.org/pdf/icg/2010/workgroupb1/03.pdf Interoperability for Liability Critical Applications], M. Azaola (GMV), International GNSS Committee, Working Group B, Special Meeting on GNSS User Positioning Integrity, Munich, 2010</ref><ref>Integrity in urban and road environments and its use in liability critical applications, J Cosmen-Schortmann, M A Martinez-Olagüe, M Azaola-Saenz, M Toledo-Lopez, Position Location and Navigation Symposium 2008 IEEEION (2008) </ref>.

	:Examples of Liability Critical Applications are road tolling, traffic law enforcement, Pay-As-You-Drive (PAYD) insurance, On-street parking pricing, Surveillance of Parolees and Fleet management (special vehicle classes).		:Examples of Liability Critical Applications are road tolling, traffic law enforcement, Pay-As-You-Drive (PAYD) insurance, On-street parking pricing, Surveillance of Parolees and Fleet management (special vehicle classes).
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	Going through a bottom-up revision of LCA and their common points and differences with SCA, ~~let us start with~~ the ~~low level aspects~~.		Going through a bottom-up revision of LCA and their common points and differences with SCA, the four main performance parameters are going to analyzed in terms of their impact in LCA and SCA.


	'''Accuracy'''		'''[[Accuracy]]'''

	:~~Taking civil aviation as an example (being one of~~ the ~~more demanding user segment in terms of GNSS navigation requirements), in civil aviation~~ performance ~~specifications~~ for ~~GNSS navigation systems impose restrictions to~~ the ~~shape~~ of ~~the distribution~~ of ~~errors~~ (~~in addition to those imposed by integrity requirements~~) by setting limits to some of its percentiles. According to the GNSS Evolutionary Architecture Study.<ref name="GEAS"> [http://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/techops/navservices/gnss/library/documents/media/GEAS_PhaseI_report_FINAL_15Feb08.pdf GNSS Evolutionary Architecture Study. Phase I - Panel Report], February 2008.</ref>, accuracy ~~performance in LPV-200 (a particular aircraft approach category that is still in process of definition)~~ is ~~specified by means of~~ a ~~standard 95% error percentile (with no associated detection requirement) and~~ also ~~by a so-called Effective Monitor Threshold (EMT), which defines a limit for~~ the ~~99.999%~~ error percentile, and errors beyond which must be detected with a probability of at least 50%. This implies that still one time out of 200,000 an error larger than the EMT could pass undetected without violating the requirements. From the point of view of civil aviation safety, ~~one out of~~ 200,000 would be ~~simply~~ unacceptable, hence ~~these requirements have~~ very little to do with safety~~, but rather with a global system performance characterisation (disregarding possible fat tails of the error distribution)~~. Therefore, although accuracy can play a key role in some safety-critical applications, that role is not as directly linked to safety as that of integrity. In a similar way, accuracy is not directly linked with liability aspects of liability-critical applications; unlike integrity, it does not help solving user liability aspects.		:SCA and LCA have accuracy requirements ensuring that the performance is adequate for the application. But from the point of view of most SCAs (such as civil aviation) it is not only required that accuracy is below a certain level, but also to be aware whenever the error falls outside the requirements. From the point of view of civil aviation safety, to have undetected errors outside the requirements with probabilities such as 1 in 200,000 would be unacceptable, hence accuracy by itself has very little to do with safety. Therefore, although accuracy can play a key role in some safety-critical applications, that role is not as directly linked to safety as that of integrity. In a similar way, accuracy is not directly linked with liability aspects of liability-critical applications; unlike integrity, it does not help solving user liability aspects.


	'''Integrity'''		'''[[Integrity]]'''

	:This is the key enabler for LCA and SCA. However, integrity requirements for LCA will tend, in principle, to be less stringent than for SCA, as the consequences of an integrity failure are much less dramatic. This is so when integrity requirements are established based on individual user’s point of view. From stakeholders’ perspective, integrity requirements might have to be established taking into account other elements necessary to make the business feasible and profitable. For instance, when a LCA involves a large number of users, integrity requirements might also aim to ~~minimise~~ the rate of user claims, in order for the application to be worthy. Also in SCA like civil aviation, this type of considerations (ultimately economic) have been made, e.g. deriving integrity requirements that account for an expected increase of air traffic operations and aim to keep the accident rate constant, thus preserving people’s perception of safety, but even such considerations have pushed in the direction of increasing (rather than relaxing) user safety.		:This is the key enabler for LCA and SCA. However, integrity requirements for LCA will tend, in principle, to be less stringent than for SCA, as the consequences of an integrity failure are much less dramatic. This is so when integrity requirements are established based on individual user’s point of view. From stakeholders’ perspective, integrity requirements might have to be established taking into account other elements necessary to make the business feasible and profitable. For instance, when a LCA involves a large number of users, integrity requirements might also aim to minimize the rate of user claims, in order for the application to be worthy. Also in SCA like civil aviation, this type of considerations (ultimately economic) have been made, e.g. deriving integrity requirements that account for an expected increase of air traffic operations and aim to keep the accident rate constant, thus preserving people’s perception of safety, but even such considerations have pushed in the direction of increasing (rather than relaxing) user safety.


	'''Continuity'''		'''[[Continuity]]'''

	:Can be essential in SCA (e.g. air navigation). A failure to provide the required continuity in aviation can have a negative impact on safety. However, in most LCA, continuity is not even a requirement, for instance, a road tolling system would require a sufficiently small protection level to be computed once in a while (depending on the topology of the road infrastructure and on the charging scheme) for road usage identification purposes. However, an aircraft needs valid positions and sufficiently small protection levels to be computed continuously for a period of time long enough to cover an entire approach and landing operation. In general we can say that the concept of continuity as different to availability usually is not a requirement for LCA although depending on the mission and on the operational concept of the application itself this could be different.		:Can be essential in SCA (e.g. air navigation). A failure to provide the required continuity in aviation can have a negative impact on safety. However, in most LCA, continuity is not even a requirement, for instance, a road tolling system would require a sufficiently small protection level to be computed once in a while (depending on the topology of the road infrastructure and on the charging scheme) for road usage identification purposes. However, an aircraft needs valid positions and sufficiently small protection levels to be computed continuously for a period of time long enough to cover an entire approach and landing operation. In general we can say that the concept of continuity as different to availability usually is not a requirement for LCA although depending on the mission and on the operational concept of the application itself this could be different.


	'''Availability'''		'''[[Availability]]'''

	:Has no safety implications in SCA and no liability implications in LCA. However, both for SCA and LCA, a poor availability performance would have a deep impact on system credibility and worthiness. For instance, in the cases of road user charging or pay-as-you-drive insurance, low availability implies that users cannot be charged (or are being undercharged) for a service that would otherwise be chargeable, and hence the ultimate recipients of the chargeable fees (governments, service providers, road infrastructure operators, insurance companies, etc.) would not get the economic profit necessary to make the system sustainable. Something similar happens for SCA; if GNSS systems do not provide enough availability for air navigation, alternative systems will have to be used, but safety is not affected. This is the only impact on SCA as long as there exists a backup navigation means, as it is the case in GNSS air navigation; there is no GNSS system certified as sole means for air navigation, whatever the navigation mode or phase of flight. Beware, however, that this could be different with other (future) safety-critical applications, provided that an adequate ~~standardisation~~ and certification entity does not exist yet, which would establish the necessary requirements at this respect to force the existence of backup systems. This could be the case of a GNSS-based autopilot system (a currently evolving idea of ADAS systems designers).		:Has no safety implications in SCA and no liability implications in LCA. However, both for SCA and LCA, a poor availability performance would have a deep impact on system credibility and worthiness. For instance, in the cases of road user charging or pay-as-you-drive insurance, low availability implies that users cannot be charged (or are being undercharged) for a service that would otherwise be chargeable, and hence the ultimate recipients of the chargeable fees (governments, service providers, road infrastructure operators, insurance companies, etc.) would not get the economic profit necessary to make the system sustainable. Something similar happens for SCA; if GNSS systems do not provide enough availability for air navigation, alternative systems will have to be used, but safety is not affected. This is the only impact on SCA as long as there exists a backup navigation means, as it is the case in GNSS air navigation; there is no GNSS system certified as sole means for air navigation, whatever the navigation mode or phase of flight. Beware, however, that this could be different with other (future) safety-critical applications, provided that an adequate standardization and certification entity does not exist yet, which would establish the necessary requirements at this respect to force the existence of backup systems. This could be the case of a GNSS-based autopilot system (a currently evolving idea of ADAS systems designers).

	So, if integrity, continuity, availability and accuracy are the critical aspects of a SCA, only integrity and availability are ~~generaly~~ the critical aspects of a LCA.		So, if integrity, continuity, availability and accuracy are the critical aspects of a SCA, only integrity and availability are generally the critical aspects of a LCA.


	== Role of Integrity for SCA and LCA ==		== Role of Integrity for SCA and LCA ==

			Therefore one of the key concepts involved in the preceding classification is integrity, as it refers precisely to the ability of the system to provide a measure of the trust that can be placed on the positioning information it provides, and to provide timely warnings when the desired level of trust is not achieved.

	In what concerns integrity, there are two main aspects to consider:		In what concerns integrity, there are two main aspects to consider:
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	From a high-level structural and ~~organisational~~ perspective, there are other aspects that make a difference between these two worlds (SCA and LCA):		From a high-level structural and organizational perspective, there are other aspects that make a difference between these two worlds (SCA and LCA):

	:'''Safety-critical applications''' tend to ignore commercial or economic aspects when establishing their standards, procedures or requirements, in order to avoid any interference of economic or commercial interests that could, otherwise, have a negative impact on safety.		:'''Safety-critical applications''' tend to ignore commercial or economic aspects when establishing their standards, procedures or requirements, in order to avoid any interference of economic or commercial interests that could, otherwise, have a negative impact on safety.