An Overview of GNSS within EUROCONTROL: Past, Present and Future
By
The
EUROCONTROL GNSS activities have been managed and carried out at the
Experimental Centre. GNSS’ staff have established a real centre of expertise in
the subject here at the EEC and this has gained world wide recognition. A
number of notable achievements have been made in the field over the last ten
years or so through the activities at the EEC. To mention but two : GNSS or
SATNAV (Satellite Navigation), as it was then referred to, gave EUROCONTROL its
first formal agreement with the European Commission and the European Space
Agency when the European Tripartite Agreement was signed in 1998 and last year,
in August, the Provisional Council approved the Common Aviation Position on
GNSS. This Common Aviation Position has the ultimate objective of using GNSS as
the sole source of navigation signals outside of an aircraft if this can be
shown to be safe and cost-beneficial. Presently, the GNSS activities are being
re-structured to put in place an action plan, with a large R & D element,
based on the Common Aviation Position. The present article gives an overview of
the EUROCONTROL GNSS activities, past, present and future, highlighting the R
& D elements.
Introduction
EUROCONTROL first became involved in
satellite navigation in 1992 through an expert group of the then Committee of
Management (COM) and the early work in 1992-93 focussed on the development of a
strategy which was approved by the COM in March 1994 and subsequently endorsed
at MATSE IV in June 1994.
The SATNAV activities were then brought
into EATCHIP, first of all as a sub-group of the Future Concepts Team and then
as an independent group. Activities mainly concentrated on Institutional
Aspects, Safety, R & D and a small amount of work on Economic Issues. The
institutional work can be considered very much as pioneering and many of the
concepts proposed (e.g. contractual chain) are still valid and very much part
of the work now done by legal services in the field of liability.
Work in the area of safety can also be
considered pioneering. Here the safety case methodology was adopted and
EUROCONTROL has played a major role in the acceptance of this methodology ECAC
wide. This in turn led to applied R & D activities in the application of a
methodology, already used in other industries, to civil aviation in general and
SATNAV in particular.
Operational test and validation of SATNAV
components provided the vehicle for an R & D programme whose main
objectives were to conceive an ECAC wide methodology and subsequently design
and develop the procedures and tools necessary to put it into effect. This work
programme was to be collaborative but centred on EUROCONTROL with the aim of
minimising costs and maximising the use of limited resources.
All aspects of the work were made as
generic as possible and not designed to meet only the needs of particular
SATNAV components or systems. In the second half of the 1990’s the only system
and component available or planned were GPS and its wide area augmentation
which more latterly became known as SBAS, the European component of which is
EGNOS. Because of the generic approach taken to all the SATNAV work, the
outcomes, originally applied to EGNOS, are now being applied to GBAS and
subsequently will be applied to Galileo.
Present Situation
With the advent of EATMP, the GNSS
Programme was set up and the work was concentrated around two major projects:
SBAS and GBAS. Similarities in the requirements of both projects led to the
adoption of a common methodology approach based on six strategic axes (see
figure 1 below).
Figure
1: Structure of the
EUROCONTROL GNSS Programme
Three of the strategic axes covering user
requirements, operation procedures and fostering standards developments are
carried out in close co-operation with the EATMP Navigation Programme. This
close co-operation has brought economies of resources and has also led to a
number of collaborative R & D activities.
The business case strategy axis has not
been greatly exploited because of staff limitations and the most significant
work done was the cost-benefit study for EGNOS in the context of civil aviation
in ECAC.
The two remaining strategic axes of safety
and operational test and validation generate the major areas of work which
follow on from the early activities in these areas as described above.
For safety related aspects, formal
relationships now exist between the SBAS and GBAS projects and the SRC which
has set up a specific group on GNSS. Safety Case activities on SBAS are, today,
very much in abeyance and awaiting decisions on the post-ESA development
framework for EGNOS. The potential (probable) EGNOS system operator and service
provider has clearly requested continued support from EUROCONTROL in the
evolution of the EGNOS Safety Case and this will include R & D activities.
Today, the safety related aspects of GBAS account for a large part of the total
work. The GBAS Safety Policy and Safety Plan were accepted by SRC at the
beginning of this year and these form the basis of the work done, much of which
is by nature applied R & D. The
application of the risk-based or goal-setting approach will accompany the
entire lifecycle of the total aviation GBAS system along the lines suggested by
the EATMP Safety Assessment Methodology.
This is very much supported by the GNSS Programme’s Stakeholders since
the outline of a GBAS Safety Case that will show by means of arguments and
supporting evidence that the concept and implementation of GBAS CAT-I precision
approach are tolerably safe is expected to serve as template for States ANSPs
own Safety Cases. As mentioned, those
activities are intrinsically R&D since the GNSS Programme is continuing its
pioneering role in the area of safety.
In the field of operational test and
validation, stakeholders supported collaborative methodologies are now in place
for both SBAS and GBAS. A major R & D effort has been made with
stakeholders to specify the procedures and tools required to carry out this
methodology and EUROCONTROL has produced the tools under the name of PEGASUS.
Prototypes of these tools are now being widely used by the participating
stakeholder community to evaluate the performance of the EGNOS signal in space
from the EGNOS Satellite Test Bed. Experience gained with the use of PEGASUS is
being fed back to EUROCONTROL and further improvements and additional
functionalities are being planned in conjunction with the user community.
Additional R & D has been required to adapt the PEGASUS tools to GBAS
specific needs and this is an on-going activity. Similarly, with the advent of
Galileo and modernised GPS, R & D will be required to find ways of
incorporating the additional functionalities offered by these systems into the
operational test and validation methodologies and supporting procedures and
tools.
Future Activities
Work within the present GBAS project is
aimed at CAT I precision approaches. A work package is included to look at the
feasibility of CAT II/III precision approaches but this activity has not yet
started due to staff shortages. Here, a large R & D effort is required
which has the full support of the stakeholder community, in particular IATA,
which participates actively in the CAT I work but sees this as only a stepping
stone to CAT II/III.
To validate the GNSS performance one of the
critical parameters is the integrity or the trust that can be placed in the
position being provided to the user.
The requirements are very strict (on the order of 10-7 per
hour) and validating that a system meets such low probabilities is not
straightforward. Research is being
performed to investigate the application of modern statistical theories such as
Extreme Value Theory (EVT) to the problem.
This also involves the use of real data from the EGNOS Test-Bed to
assess the feasibility of the theoretical techniques.
Following a recent flight trial to evaluate
GNSS approaches into Nice Airport, the recorded data were analysed to produce
noise contours which were compared to those determined using recorded radar
data from classical approaches. An R & D programme on environmental aspects
would investigate the potential benefits of using GNSS in terms of noise
nuisance around airports, fuel burn and emissions.
EUROCONTROL has co-ordinated the
development of a common civil aviation position paper, with airspace users
ANSP’s and States, on GNSS which has been approved by the Provisional Council.
In this paper a “sole-service” concept is proposed for all phases of flight
where GNSS is the only radio-navigation aid available outside of the aircraft.
An initial feasibility study on the “sole-service” concept has been launched
but much further R & D is required here.
Sceptics of GNSS use very much the
vulnerability of GNSS signals as an argument against the “sole-service”
concept. Again an initial study has been started to assess the vulnerability of
an ECAC Navigation Infrastructure based on GNSS but much more R & D needs
to be done to assess both unintentional and intentional interference, their
probabilities of occurrence and possible mitigation techniques. A debate is now
beginning on the safety and security aspects of interference, which are the
civil aviation responsibilities (safety) and which are institutional, state
responsibilities (security).
EUROCONTROL has also played a major role in
finding a common way forward for civil aviation in the EGNOS context. The EC
will propose to the March EU Transport Council the integration of EGNOS into
Galileo which will facilitate the operational availability of Galileo. This
proposal is supported by IATA which sees Galileo as very much a part of the
“sole-service” concept which they advocate. The EC plans an aggressive
programme to develop the user segment of Galileo using EGNOS facilities and
sees EUROCONTROL as the focal point of this activity for civil aviation. For
this, an R & D campaign has to be put in place to investigate operational
benefits from GNSS not only in ECAC but in bordering states and beyond as well.
Finance for such an activity would be available through the Galileo Joint
Undertaking and the 6th Framework Programme.
Co-operation with AOP should lead to the
development of requirements for the use of GNSS positioning capabilities within
an A-SMGCS to increase safety and capacity under increased traffic and low
visibility conditions. R & D is required to provide evidence of the
capability of GNSS to meet the identified requirements.
Safety related studies are looking at the
principle of a risk-based approach to assess risk estimates against appropriate
criteria. To date ESARR4 only mentions
a quantitative definition for the maximum tolerable probability of ATM directly
contributing to an accident of a Commercial Air Transport aircraft. Quantitative safety objectives associated
with the maximum tolerable probabilities of ATM directly contributing to
incidents remain to be determined and in order to deal with specific
constituent parts of the ATM system (sub-systems), the overall ATM figures have
to be refined so that they adequately reflects the operational environment of
the sub-system under consideration. The
GNSS Programme is co-ordinating an R&D activity together with SRU, SQS and
the SAF Business Area at the EEC to develop a methodology to derive figures for
sub-systems whose feasibility will be demonstrated by its application to
GBAS. In addition, in order to support
the aforementioned risk-based approach, the GBAS Project will demonstrate the
applicability to ATM of common technique in non-aviation domains, e.g. the
combination of fault trees and event trees to represent the full complexity of
the GBAS system and identify key areas contributing to risk escalation and
common cause analyses to analyse dependencies.
Finally, since human factors and procedural aspects are keys in the
safety assessment process, the GBAS Project will concentrate on the application
of Human Reliability Assessment (HRA) techniques to civil aviation for the
quantification of the likelihood or probabilities of human error. Those activities are by definition applied
R&D.
A feasibility study is underway to assess
how raw GNSS signals in space can be used to determine water vapour content of
the atmosphere and be used as additional input to Numerical Weather Predictor
models to improve Meteorological Forecasting particularly with respect to
icing, fog, weather fronts and thunderstorms and to estimate benefits to civil
aviation. Results so far are extremely promising and go as far as to show that,
for example, airports equipped with a small number of GNSS receivers could
provide accurate weather forecasts independently of met. services. Also, from
this feasibility study, it seems possible to determine an accurate tropospheric
model which could be used in an SBAS system to further enhance accuracy. Again,
further R & D needs to be done to follow-up these initial findings.
GNSS is by nature multi-modal and is seen
by the EC as important part of TEN-T infrastructure. R & D needs to be done
to look at the possible rationalisation
of GNSS components for different modes of transport to further increase
safety and reduce overall infrastructure costs.
Conclusions
This article has attempted to highlight the
R&D activities carried out in the field of GNSS. A look has been taken of the situation pre-EATMP as well as a
review of the present activities under EATMP.
Finally, an overview of future activities has been made. Some of these R&D activities are already
underway, others are undergoing feasibility studies to facilitate the planning
of future work and some are in the negotiation stage with potential partners.
All of the R&D activities described in
the paper have a wide range of stakeholder support and all are carried out in a
collaborative manner both through stakeholders participation and through co-operation
with other Agency programmes, units and business areas.
The paper clearly shows that R&D has
played, is playing and will continue to play an important part of the
EUROCONTROL GNSS activities.
Abbreviations
MATSE IV Ministers
of air Traffic Services in Europe (4th Meeting)
SATNAV Satellite
Navigation
EATCHIP European Air Traffic Control
Harmonisation and Integration Programme
ECAC European Civil
Aviation Conference
GPS Global Positionning
System
SBAS Space Based
Augmentation System
GBAS Ground Based
Augmentation System
EATMP European Air Traffic
Management Programme
EGNOS European Geostationary
Navigation Overlay Service
EU European Union
ESA European Space
Agency
EC European
Commission
SRC Safety Regulation
Commission
ANSP Air Navigation Service
Provider
GNSS Global Navigation
Satellite System
IATA International Air
transport Association
AOP Airports Operations
Unit
A-SMGCS Advanced Surface Movement
Guidance and Control System
ESARR EUROCONTROL Safety
Regulations Requirements
ATM Air Traffic
Management
SRU Safety Regulation
Unit
SQS Safety, Quality
Management and Standardisation Unit
SAF Safety Business
Area
EEC EUROCONTROL
Experimental Centre
TEN-T Trans European Networks
- Transport