GIS Mapping and Automatic Vehicle Location (AVL) Technology
An overwhelming increase in the volume of commercial air traffic in the last half of the twentieth century has increased the demand on aircraft ground taxiing (known as surface movements) at the world’s airports. This change resulted in a corresponding increase in the potential for runway incursions, both by unauthorized aircraft and by ground vehicles outside of their operating locations. The problem created by the increase in volume culminated in the most serious ground accident in the history of aviation at Tenerife, in the Canary Islands of Spain on March 27, 1977, when two 747 airliners collided in the fog with catastrophic loss of life.
Many international organizations such as NASA, the Flight Safety Foundation, and universities such as Stanford University and Ohio University have made significant strides toward the implementation of enabling technology to reduce runway incursions and to enhance the efficiency of airport surface operations.
Early solutions included the implementation of Surface Movement Guidance and Control System (SMGCS) at a number of airports. An SMGCS has a number of lights and sensors that control taxiing operations. Subsequent follow-on work with multilateration radar technologies is in progress to enhance tools for air traffic control authorities (known as Air Traffic Management or ATM) to control airport surface movements.
However, display technology was also needed to provide flight and, potentially, ground vehicle crews with enhanced situational awareness, which required a moving map of the airport. The primary goal is to give pilots “synthetic” views of their positions on the airport, as if they could actually see outside in clear daylight weather conditions. With the publication of a global GIS standard known as DO-272, airports could be consistently mapped in order to provide that needed situational awareness.
Figure 1 is an example of such an airport mapping database (AMDB), constructed by Space Imaging’s Solutions organizations. One of the significant “enabling technologies” necessary to adopt the widespread use of airport mapping is the ability to define and exchange position information. The recent implementation of the GPS Wide-Area-Augmentation-System (WAAS) constellation by the Federal Aviation Administration (FAA) greatly enabled geopositioning. Instead of a location solution that was no better than 25-50 meters, the WAAS improved the quality of raw GPS to 1-2 meters laterally, and 2-3 meters vertically.
These AMDBs would have multiple uses, including surface movement awareness information for air traffic controllers, for flight crews and for ground vehicles. Other uses include graphical depictions of future changes to support future trips and Homeland Security surveillance and response needs. New GIS, satellite imagery and GPS technology have allowed airports to more effectively manage these needs.
Following the tragic events of 9/11, a stronger emphasis was placed upon the security of air traffic, not just the safety of air traffic. Once steps were taken to better secure air traffic in-flight (with reinforced cockpit doors, air marshals and improved screening), the security of surface movements became more of a focus for improvement.
The airport “environment” is comprised of fixed and movable assets. The airport mapping database (AMDB) will take care of mapping the fixed or permanent installations on the airport, both airside (where the aircraft can actually taxi) and groundside (all areas of the airport not used for aircraft taxiing). However, AMDB cannot track movable assets, which are principally ground vehicles.
Tracking ground vehicles for flight operations coordination is the primary concern. Other requirements include:
(a) Tracking ground vehicles for asset management purposes
(b) Tracking ground vehicles for operational efficiency
(c) Tracking ground vehicles for security surveillance
(d) Tracking ground vehicles for flight operations emergency response
(e) Tracking ground vehicles for terrorist or security emergency operations.
At any given airport, it is likely that 10 to 20 times the number of ground vehicles exist as do aircraft. Since any truck can potentially carry explosive or hazardous cargo, airport authorities need to find better ways of monitoring their locations.
|Figure 2: Example ofAVL with authorized areas for baggage carts and fuel trucks in yellow.|
AVL (automatic vehicle location) example: Baggage carts and fuel trucks ought to stay on the “thatched aprons,” or yellow taxiways. They should never be on the red runways (Figure 2).
Fortunately, the trucking industry worldwide has been using a technology known as automatic vehicle location or AVL for much of the past several decades. The principal components of an AVL system include:
(a) GPS receiver and a wireless data link in each remote vehicle
(b) Master station, capable of receiving all data link transmissions from the remote vehicles
(c) Capture software and data logging, capable of replaying portions or complete routes being driven by the remote vehicles
(d) Mapping and/or monitoring software to track the vehicles’ positions.
Initially, AVL required explicit polling of the vehicles, as radio transmission speed was limited. With the implementation of cellular analog and then digital transmissions, those speeds increased by many orders of magnitude.
With this increased bandwidth, it has become feasible to monitor the exact routes being used as well as the speed and directions of the vehicles. This close monitoring allows the detection of unlawful movements and triggers alarm conditions when the vehicle strays significantly from a planned routing or location. Driver identification using a smart card or similar digital signature to attach a “person” to a “vehicle” is a simple matter.
Much like air navigation, AVL supports progressive monitoring of a route from location to location, including complete velocity and direction that can be refreshed to the second. With the low driving speeds found in surface movements, it is fully feasible to use this type of technology to report on the movement of ground vehicles on an airport, at any size airport in the world.
Figure 3: AVL Behavior Example: Perimeter Security Vehicle should pass along the black roadway along the shoreline at least once every two hours.
|Figure 3: AVL behavior example of route for security perimeter vehicle.|
One of the significant advantages of AVL technology is the ability to observe or monitor the behavior of the ground vehicles, not just the position. If we re-examine the table from the previous paragraphs, we can assign some kind of behavior to each of those categories. This would allow us to define when the actions of the vehicle are not consistent with the expected behavior and thus need to trigger an alarm.
Following is a list of ground vehicle monitoring purposes and the behavior to observe.
Asset Management Purposes
Can we identify the location?
Can we identify the driver?
Has the driver of this vehicle surpassed his/her hours on the job?
Is the vehicle being operated during its known hours of operation?
Has a vehicle exceeded the speed for its chosen task?
Has the vehicle gone from a state of transmission to silence?
Has a security vehicle driven along the entire fence/perimeter in the past “period of time?”
Has a vehicle gone outside the known area of operation for this type of vehicle?
Has a vehicle exceeded the speed for its chosen task?
Has a vehicle gone from a state of transmission to silence?
Is the driver of this vehicle qualified to operate the vehicle in restricted areas (such as fuel farms customs areas or hazardous material storage)?
Flight Operations Emergency Response
Can we identify the vehicles that are trained to respond to this type of emergency?
Can we identify that those vehicles are equipped with drivers trained in that purpose?
Can we identify that all other vehicles have left the area of the emergency?
Can we identify if any vehicles are impeding the response to the emergency?
Terrorist or Security Emergency Operations
Can we identify other vehicles from external agencies needed to respond to the threat (National Guard, Police, Fire or TSA)?
Can we ensure that those vehicles not responding to the threat are kept away from the area of the threat?
In the increased level of security that has become commonplace in the airports of the world, several new geospatial technologies have combined to assist enhanced monitoring of ground vehicles. Those technologies include:
(a) GIS databases of the airports, AMDB. These support vector mapping of the airport at positional accuracies down to 1 meter RMSE, when derived from high-resolution satellite imagery.
(b) The Wide-Area-Augmentation-System implemented by the FAA, which allows positioning vehicle and aircraft on the above maps to within 1-2 meters.
(c) Widespread and economical availability of wireless and cellular bandwidth.
(d) Automatic Vehicle Location (AVL) technology that can combine all of the above to enable strict monitoring of airport ground vehicles.