Advanced-Surface Movement Guidance and Control Systems

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Advanced-Surface Movement Guidance and Control Systems

43RD ANNUAL CONFERENCE, Hong Kong, China (SAR), 22-26 March 2004

WP No. 94

Advanced-Surface Movement Guidance and Control Systems

Presented by SC1


1.1. As part of the 2003/2004 work program, SC1 was tasked to review existing policy on Surface Movement Guidance and Control Systems (SMGCS).

1.2. During this review, it became clear that a distinction had to be made between SMGCS and Advanced-SMGCS (A-SMGCS). This paper addresses A-SMGCS.


2.1. SMGCS consists of the provision of guidance to, and control or regulation of, all aircraft, vehicles and personnel on the movement area of an aerodrome.

– Guidance: Facilities, information and advice necessary to enable pilots and drivers to find their way.

– Control or regulation: Measures necessary to prevent collisions and to ensure smooth and free traffic flows.

SMGCS comprises an appropriate combination of visual and non-visual aids, procedures, control, regulation management and information facilities. SMGCS procedures are based primarily on the “see and be seen” principle.

2.1.1 Guidance

Guidance is performed by ATCO’s by giving instructions or manually operating stop bars and taxiway lights. Pilots and drivers rely on visual aids.

2.1.2 Control

Surveillance is performed visually by the ATCO. Visual observation by ATCO’s, pilots and drivers allow estimating respective relative positions and collision risk. Handover of control is done procedurally. Varieties of techniques and procedures are currently applied in Europe.

2.1.3 Low Visibility Procedures (LVP)

Procedures vary from aerodrome to aerodrome depending on ATS regulations and policies, organisational responsibilities and the aerodrome configuration and facilities. Low visibility SMGCS procedures are followed according predetermined meteorological conditions. Aircraft operators are informed by means of ATIS. The use of Surface Movement Radar (SMR) during low visibility conditions is limited and SMR may not be used as the basis of decision making.

2.2 Since the existing systems demonstrate weaknesses in coping with the present situation, future systems should tackle the following concerns and needs:

  • Degradation of safety: Accidents during taxi phase in Western Europe and North America represent two thirds of the world-wide number of accidents. The number of such accidents is increasing.
  • All weather operation: Low visibility procedures curtail the overall ATM capacity and impede apron activities. The application of new technologies will help airports maintain their throughput when visibility is reduced.
  • Technology deficiencies: The most developed SMGCS are based on SMR. This technology has presented some deficiencies (loss of target due to masking, plot clutter due to rain, label overlap, etc.). Those elements combined with false alarms from associated conflict detection and alerting systems, cause ATCO’s to express a lack of confidence in the system.
  • Technology cost: Currently adequate equipment is expensive and therefore only implemented for major airports. ATM providers and airport operators expect less expensive A-SMGCS.
  • Capacity optimisation: Due to the current capacity shortfall at all major ECAC airports, there is a need for equipment that generates efficient flows of aircraft and allows optimum arrival and departure streams. Further integration of airport scheduling with flow and capacity management should be the goal.
  • ATC procedures: Local practices, such as multiple line-up or conditional clearances, are not always conform to ICAO Standards. Some conflict detection tools misinterpret situations and cause false alarms. ATCO’s disturbed by false alarms tend to disable such functions.
  • Aerodrome activities co-ordination: Sharing of operation data between ATC and all airport operators is required to improve aerodrome activities co-ordination.

2.3 The concept of A-SMGCS was introduced at the end of the 1980s, following the increase in airport traffic and in runway incursion incidents. ICAO has defined the operational needs for A-SMGCS in general terms and has described a modular system with several functions. According to ICAO A-SMGCS is: Systems providing routing, guidance, surveillance and control to aircraft and affected vehicles in order to maintain movement rates under all local weather conditions within the Aerodrome Visibility Operational Level (AVOL) whilst maintaining the required level of safety. The ICAO manual on A-SMGCS is expected to be published in 2004.

2.4 One of the focus points of EUROCONTROLs ATM 2000+ Strategy is making the best use of airport airside capacity through the application of new concepts and procedures supported by improved technical systems. The A-SMGCS concept is considered essential to achieve these objectives. Improvement of traffic management on the movement area by enhancing traffic situation awareness in all weather conditions is the goal.

2.5 An A-SMGCS will build on existing SMGCS aids, procedures and practices, but with the added support of new or emerging technology to maintain safe and efficient airport airside operations in all weather conditions (extreme conditions such as blizzards, freezing rain, heavy thunderstorms etc. excepted) The main differences will lie in the transition from the present procedural system, in very low visibility involving for pilots respectively controllers numerous voice reports, clearances and instructions and for vehicles voice reports, authorisations and instructions, to ideally a fully automated system, involving automatic tracking, automatic guidance and control as far as possible of all mobiles. This will have to be accomplished through a managed process of ever more sophisticated implementation levels as technology evolves and subsequent progressive and modular introduction of respectively new surveillance technologies (multilateration, multi-SMR with labelling etc.), improved aircraft, ATC & airport systems automation and improved data sharing. This will in turn call for changes in apron management and ATC procedures. The first change will be in the use of surveillance sensors and displays as a control tool in aerodrome control (and apron management).

2.6 A-SMGCS definition from a users point of view:

  • Surveillance: ATCO’s and eventually pilots and drivers shall be provided with situational awareness. Identity and position of all traffic should be provided in an adequate update rate. The need to cover the movement area is recognised but is due to existing technology, procedures and ATC services restricted to the manoeuvring area. In the short term A-SMGCS should not cover the apron except for aircraft. Co-operative surveillance is required, target need to be equipped. Some means of surveillance is required to detect non co-operative targets and obstacles. Several sensor systems combined by a data fusion process will provide a comprehensive surveillance package.
  • Routing: A more sufficient route is designated manually and eventually automatically for each aircraft or vehicle. This function shall be capable of meeting the needs of dense traffic patterns at complex aerodromes and does not constrain the pilot’s choice of a runway exit after landing. The routing function will be improved through phased A-SMGCS implementations.
  • Guidance: A guidance function shall give pilots and drivers clear indications to enable them to follow an assigned route, to maintain situational awareness of their position and to monitor the operational status of all guidance aids and providing on-line monitoring with alters.
  • Control: The control function shall prevent conflicts and collisions by providing alerts for runway incursions and activating protective devices. Warnings are issued to the controller and possibly direct to pilots and drivers concerned. The control function does not replace the controller but gives automatic assistance in the control task. A supporting planning function should be introduced in order to achieve maximum benefits. This function provides strategic, pre-tactical and tactical planning.

2.7 A-SMGCS as a surface management system will form a part of the global Communications Navigation Surveillance Air Traffic Management (CNS/ATM) concept in terms of supporting gate-to-gate operation, rather than merely being used to provide guidance and control to individuals.

2.8 Areas of change between SMGCS and A-SMGCS:

  • Surveillance: Provision of accurate and reliable surveillance data from independent or cooperative sensors are required. A-SMGCS are intended to complement visual information of the ATCO, especially when visibility is reduced.
  • Rules of ground movements: The evolution of the “see and be seen” principle requires first the definition of a new set operational rules to be applied by ATCO’s, pilots and drivers. This includes:
    • definition of procedure to use A-SMGCS
    • definition of rules for authorised mobiles and movements on the manoeuvring area (for identification procedures in All Weather Operations (AWO), conditional clearances, multiple line-up, etc.) and finally definition of separation rules.
    • definition of the conditions in which such procedures can be applied (weather, system status, etc.)
  • Pilots and drivers in the safety loop:
    The challenge will be to provide improved guidance, particularly in low visibility conditions, without increasing the workload. The main contribution of A-SMGCS is the increase in ground traffic situation awareness for pilots and drivers who play the same role as the ATCO in the ground safety loop. Since ground accidents occur through safety loopholes made by ATC procedures, pilots and drivers constitute an additional protection shelter.
  • Ground safety net:
    When operational rules are broken, automated tools adapted to ground hazardous situation detection will inform ATCO’s, pilots or drivers in due time. To avoid disturbing actors (false alarms) fine adaptation of such tools is necessary to detect:

    • unidentified or unauthorised aircraft/vehicles
    • prohibited movements
    • risk of collision
  • Efficiency of ground movements:
    Implementation of A-SMGCS also aims at contributing to gate-to-gate operations as well as to the other airport actors. Thus the introduction of a planning tool of ground movements is required, taking into account needs from arrival/departure ATCO’s (CFMU slots), airport operator (gate management), airlines (fleet planning, hub connections, turn around) and airport resource management (maintenance, capacity management).

2.9 For aircraft operations and avionics systems installed on board, a certification process is well defined and universally applied. For ground systems, service providers often specify the system with regard to available standards and recommended practices, but will commission the system without independently agreed and harmonised safety objectives. Safety aspects not only of the equipment on board but also of the system or service as a whole need to be addressed when adopting a certification process.

An “end to end” certification is being proposed for all new ATM system concepts where there is an integration of new technology in airborne and ground elements and utilisation of advanced automation techniques. New certification procedures for A-SMGCS may result in implementation delays.

2.10 Some of the major airports in Europe have initiated the implementation of ASMGCS but with different operational concepts and approaches:

  • EDDF: TACSYS/CAPTS surveillance system includes a X-band SMR, a millimetre wave SMR, CAPTS Multilateration system capable of ADS-B, no vehicle tracking.
  • LFPG: AVISO system includes surface radar ASTRE, vehicle positioning system SYLETEACK, anti-collision system SALADIN.
  • ESSA: X-band radar systems and ADS-B transponder for aircraft and vehicle localisation and identification, runway incursion detection.
  • EBBR: Use of SMR and Mode S Multilateration is planned for surveillance, alerting tools.
  • EGLL: Use of SMR and Mode S Multilateration, runway incursion detection.
  • LSZH: Implementation of Mode S Multilateration is planned.
  • EHAM: Implementation of Mode S Multilateration is planned.
  • LOWW: ASTOS Sytem including Ku-Band Radar (ASTRE 2), Mulutilateration System capable of ADS-B, flightplan data base, MET data, Directionfinder (DF), Aerodrome Surveillance Radar (ASR), runway incursion detection. Vehicle position system is planned.

2.11 Implementation requires definition of new procedures for the system users. A reassignment of responsibilities among A-SMGCS actors is possible. There is a significant risk related to the user’s acceptance of these procedures and the fact that these new procedures could have a negative impact on safety.

False alarms generated by ineffective systems will not be accepted by the controller. It is extremely difficult to identify all possible conflict cases taking into account local procedures so as to avoid false alarms.

High costs of new systems may cause aircraft operators to refrain from implementing the technology. The costs of the system will drive the choice of the type of A-SMGCS to be implemented. This choice will be local depending on each airport implementation.

2.12 Implementation of A-SMGCS on an airport is dependent of the traffic density, on the aerodrome lay-out and if the airport is affected by low visibility conditions.

ICAO defined three airport categories by the traffic density, thereby taking account of the mean peak hour:

  • Light traffic which is characterised by a peak not greater than 15 take-offs or landings per runway or typically less than 20 total aerodrome movements.
  • Medium traffic which is characterised by a peak comprised between 16 to 25 take-offs or landings per runway or typically between 20 and 35 total aerodrome movements.
  • Heavy traffic which is characterised by a peak of 26 or more take-offs or landings per runway or typically more than 35 total aerodrome movements. The traffic density parameter could be completed by the notion of the annual number of movements:
  • First threshold light/medium: between 40.000 and 60.000 movements per year.
  • Second threshold medium/heavy: between 140.000 and 160.000 movements per year.

Another aspect is the mix of arriving and departing movements, which means crossing flows of aircraft.

ICAO defined three categories of aerodrome layout:

  • Basic: An aerodrome with one runway and one taxiway to one apron area.
  • Simple: An aerodrome with one runway, having more than one taxiway to one or more apron areas.
  • Complex: An aerodrome with more than one runway, having many taxiways to one or more apron areas.

Other parameters that make a layout complex:

  • An Airport has a taxiway system with a great number of apron intersections.
  • A taxiway has to be shared by landing and departing aircraft or by aircraft and vehicles at the same time.

ICAO defined four levels of visibility conditions in the A-SMGCS manual:

  • Condition 1: Visibility sufficient for the pilot to taxi and to avoid collision with other traffic on taxiways and at intersections by visual reference, and for personnel of control units to exercise control over all traffic on the basis of visual surveillance.
  • Condition 2: Visibility sufficient for the pilot to taxi and avoid collision with other traffic on taxiways and at intersections by visual reference, but insufficient for personnel of control units to exercise control over all traffic on the basis of visual surveillance.
  • Condition 3: Visibility sufficient for the pilot to taxi but insufficient for the pilot to avoid collision with other traffic on taxiways and intersections by visual reference, and insufficient for personnel of control units to exercise control over all traffic on the basis of visual reference. For taxiing this is normally taken as visibilities equivalent to a RVR less than 400 m but more than 75 m.
  • Condition 4: Visibility insufficient for the pilot to taxi by visual guidance only. This is normally taken as a RVR of 75 m or less.

An aerodrome is affected by low visibility conditions when condition 3 and 4 are met during more than 15 days a year.

2.13 From a tower/ground controllers view, three types of visibility are known:

The ATCO is:

  • Able to see the entire field
  • Able to see parts of the field
  • Not able to see the ground

Actually application of any kind of procedures is primarily based on these observations. In case the ATCO is not able to see the concerned traffic, he/she has to rely on pilots or drivers reports on their current visibility.

Since there are no new techniques yet to determine accurate visibility for any part of the airfield, these procedures will not change significantly whether application of low visibility taxiing procedures is officially based on RVR values.

2.14 EUROCONTROL through it’s A-SMGCS project proposes implementation of ASMGCS via Implementation Levels (I to IV).

These Implementation Levels form a coherent series that:

  • recognises operational needs
  • reflects the evolution of technologies and procedures
  • enables airports to equip according to local requirements

The main concerns of level I and II rely on the improvement of safety. Ground movements efficiency is dealt within levels III and IV.


Level I: Corresponds to the shorter step in terms of urgency, technology and cost.

  • Surveillance: ATCO’s will be provided with position and identity of all aircraft in the movement area and all co-operative vehicles in the manoeuvring area. Aircraft and vehicles are expected to be co-operative. It should also be possible for ATC to cope with a very limited number of non co-operative mobiles.
  • Guidance: Guidance continues to be performed as in the current SMGCS.
  • Route Planning: Is not foreseen at this level.
  • Control: Is not foreseen at this level.

Level II: Improvement of Level I existing functions and in the introduction of the control and guidance function.

  • Surveillance: Will be the same as in level I.
  • Guidance: A guidance service for vehicles based on GNSS will be provided to vehicle drivers as an option.
  • Route Planning: Is not foreseen at this level.
  • Control: An initial control function will be introduced in order to detect the most hazardous conflicts (runway incursions) and alert the controller in due time. Harmonisation of local working methods (multiple line-ups, conditional clearances, etc.) will be beneficial.

Level III: Complementation of Level II functions with the sharing of situational awareness amongst pilots and drivers and the introduction of the automated routing function.

  • Surveillance: The surveillance function provided to the controller at Level II will be delivered and shared with pilots and drivers. Implementation of technologies like ADS-B / TIS-B will be required. Non co-operative sensors will be still necessary in order to detect intruders.
  • Guidance: Level II guidance function will be improved by displays of maps and mobile positions, providing and update of the runway status and triggering automatically dynamic ground signs according to the route issued by the controller.
  • Route Planning: On the basis of a planning function a route planning function shall determine the best route taking into consideration possible delays, potential conflicts and ground rules. This function will be provided to controllers only.
  • Control: Based on Level III surveillance function the control function will be able to detect any conflict concerning mobiles on the movement area. The alarms will be provided to ATCO’s and pilots and drivers.

Level IV: Improvement of the functions implemented in Level III.

  • Surveillance: Will be the same as in Level III
  • Guidance: Will be the same as in Level III
  • Route Planning: The proposed route will be down-linked to pilots and drivers after validation by the ATCO.
  • Control: The control function will be provided to ATCO’s, pilots and drivers in the movement area and will e complemented by a conflict resolution function.

2.16 Currently few airports in Europe have full SMGCS capabilities (SMR, stop bars, etc.) although a number of them encountered runway incursions. Equipping airports with SMR is a matter of cost of the system. For a strategy for A-SMGCS implementation in Europe A-SMGCS categories (low, medium, high cost) and airport typologies have been identified.

Airport Type (Density) A-SMGCS Cost Surveillance Control Route Planning Guidance
Light No (full) A-SMGCS Partly Partly
Medium Low Cost I / II II II
Medium with complex layout or more than 15 low visibility days Medium Cost I / II III III III
Heavy High Cost III / IV IV IV IV

2.17 An extensive collection of phraseology for A-SMGCS procedures is currently being developed. For example, the meaning of the term “hold short of…” for taxiing aircraft is not clearly defined and thus lead to uncertainty of pilots and ATCO’s. This issue does concern not only A-SMGCS but ground control in general.

2.18 Using the term “separation” used for spacing between mobiles on ground (except runways) needs consideration in order to avoid confusion or misinterpretation, especially when the term “runway separation” is also used.

2.19 When developing new procedures, it shall be done in a way to achieve complete acceptance by the ATCO.


3.1. SMGCS procedures are based on “see and be seen” principles, therefore effective operations can only be maintained as long as visibility is sufficient for all persons involved.

3.2 The provision of A-SMGCS enables efficient operations to be maintained by the provision of reliable situational awareness. This is achieved by means of target identification and labelling.

3.3 EUROCONTROL, through it’s A-SMGCS project, proposes implementation of ASMGCS via Implementation Levels (I to IV)

3.4 New procedures and/or phraseology are being developed to support A-SMGCS implementation. These procedures have to be developed in a way to achieve complete acceptance by the ATCO. The introduction of A-SMGCS procedures and equipment should be associated with appropriate training and due consideration for controller workload.

3.5 IFATCA supports the implementation of A-SMGCS as an enhancement to safety, particularly with regard to runway incursions and low visibility procedures.


It is recommended that;

4.1 This paper is accepted as information material.

Last Update: September 29, 2020  

March 25, 2020   996   Jean-Francois Lepage    2004    

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