Related Applications

This application claims the priority of U.S. provisional patent application serial no. 61/156,001 filed on February 27, 2009.

Field of the Invention This invention relates to airport safety systems for vehicles, particularly airport service ground vehicles, and more particularly to systems providing warning signals to prevent contact with vehicles on airport runways with aircraft.

Background of the Invention Besides airplanes, airports have a number of movable ground vehicles, the term vehicles here being broadly meant as any kind of moving apparatus or machine, such as service vehicles, lawn mowing equipment, luggage trucks, boarding ladders for aircraft, or a host of other maintenance or security vehicles, that move around in the area of the airport on the ground and provide services to enable the airport to function. The areas of operation of these vehicles or machines often includes or is contiguous to runway areas on which the aircraft land or take off, or taxi.

The ground vehicles are sometimes driven onto the runways themselves, where the airport space is potentially shared by the ground vehicle and airplanes. Generally, this constitutes a "runway incursion", which has obvious potential for negative interaction or collisions between the ground vehicle and an airplane travelling along the runway or taxiway. When there is a runway incursion, the airport vehicles usually are equipped with various types of warning lights or annunciator light systems, such as flashing dome lights similar to a police car flashing light system in which bright light sources flash and rotate. These annunciator lights make the vehicles more visible to any planes in the vicinity _^ and to the control tower, and make the vehicle difficult to overlook in the event of a runway incursion near an aircraft Typically, the warning annunciator light is turned on manually by the operator when the vehicle or machine is driven onto a runway. However, there is a possibility that the operator will forget to affirmatively turn on the warning light, and drive the airport ground vehicle onto the runway without the warning light on. This type of runway incursion might, in certain visibility conditions, lead to an undesirable contact or interation of the movable vehicle with an aircraft while landing, taking off, or taxiing on the runaway.

Summary of the Invention It is accordingly an object of the invention to provide a unit that provides a warning light that automatically turns on when the unit moves onto a runway, and that extinguishes the warning light when the unit laves the runway.

According to an aspect of the invention, a warning light system for an airport vehicle has a warning light carried on a movable vehicle and a power controller linking the warning light to an electrical power source, selectively causing the electrical power to flow to the warning light such that the warning light illuminates and to interrupt flow of the electrical power to the warning light such that said warning light is not illuminated. Control circuitry connected with the power controller determines whether or not a geographical position of the vehicle indicated by a GPS receiver on it is within a predefined geographical area. Responsive to a determination that the vehicle is within the predefined geographical area, the control circuitry causes the power controller to illuminate the warning light. Responsive to a determination that the vehicle is not within the predefined geographical area, the control circuitry causes the power controller to interrupt flow of the electrical power to the warning light such that the warning light is off. The warning light as a result illuminates without any action by a user when the vehicle enters the predefined geographical area and is extinguished when the vehicle leaves the predetermined geographical area.

According to another aspect of the invention, an airport vehicle comprises a self- powered vehicle configured to move about on an airport grounds. The vehicle supports thereon an annunciator warning light, and a GPS receiver continually transmitting electronic location data indicative of a location of the vehicle. Control circuitry connected with the GPS receiver receives the electronic location data from it. Electronic data storage memory connected with the control circuitry stores geographical data defining a restricted access area of the airport grounds in which the vehicle is required to have the annunciator warning light illuminated. The control circuitry continually determines from the location data and the geographical data if the vehicle is in the restricted access area. Responsive to a determination that the vehicle is in the restricted access area, the control circuitry activates the annunciator warning light.

According to still another aspect of the invention, a method of providing an annunciator system light to a vehicle comprises installing a warning light system as described above on a vehicle

Most commonly, the unit will be mounted on an airport vehicle and be powered by its electrical system. Alternatively the unit may have a battery power source for its operation and the light.

The unit contains data storage preferably storing runway location data defining all the runways in the given airport, or in any region, e.g., the entire U.S. airport system. The unit has an antenna that receives navigation location data, e.g., WAAS, GPS, or whatever system is available, and determines the location of the unit. The navigational data is compared by an electronic circuit or computer system in the unit to determine if the unit's location is on a runway. If so, the circuit or system switches power on to the warning light causing it to strobe or illuminate so that an aircraft nearby can see it and avoid the person or vehicle with the unit. When the determination is that the unit is not on a runway, the warning light is switched off.

Other objects and advantages of the invention will become apparent from this specification.

Brief Description of the Drawings

Fig. 1 is a plan view diagram of a portion of an airport, showing movement of an airport service vehicle and schematically illustrating the operation of its selectively illuminated warning light. Fig. 2 is an elevational view of an exemplary airport vehicle provided with an annunciator light unit according to the invention, with its warning light illuminated. Fig. 3 is a detailed view of an annunciator warning light unit according to the invention.

Fig. 4 is a schematic illustration of the general functional components inside an annunciator warning light unit according to the invention. Fig. 5 is a more detailed schematic view of the various components and constituent parts of the warning light apparatus according to the invention.

Fig. 6 is a flow chart illustrating the overall operation of the warning light unit according to the preferred embodiment operating according to a microprocessor.

Fig. 7 is a flow chart illustrating the operation of the GPS-based location detection and warning light operation of the warning light unit according to the invention.

Fig. 8 is a schematic illustration of a communications network at an airport communicating with a number of annunciator light units at the airport.

Detailed Description Referring to Fig. 1 , an airport is normally provided with a number of runways 3 and other aircraft movement roadways 5, which are preferably dedicated to having only aircraft on them unless it is necessary for some vehicle or service device to be brought onto the runway 3 or 5.

The airport also usually will have adjacent to those runways a variety of areas, indicated generally at 7, 8 and 9, that are not runways but that require some activity such as grass being cut or have other uses that require the presence of vehicles other than aircraft. A vehicle of an exemplary type is shown, indicated at 11. This vehicle has a warning light, 13, preferably on its roof or in some position where it can be seen from a wide range of angles, including above by aircraft in flight. This vehicle 11 is driven on the airport land on an exemplary route 15 in Fig. 1 that traverses the runways 3 and the taxiway 5. When the vehicle, 1 1, is in an area which is not an aircraft operational area, such as runway 3 or taxiway 5, e.g., positions A ₅ B, C and D, the rooftop light, 13, remains extinguished. However, when the vehicle, 11, enters onto any aircraft operational area, i.e., runway 3 or the taxiway 5, the rooftop annunciator warning light 13 is illuminated, as schematically illustrated in Fig. 1 at intermediate positions E, F and G. Referring to Fig. 2, an exemplary airport vehicle 11 is shown in elevational view. The vehicle 11 can be any vehicle of any configuration, e.g., a security vehicle, a fire truck, an ambulance, a grounds-keeping vehicle, a lawnmower, or virtually any kind of vehicle that moves on the airport grounds. The airport vehicle itself is provided with the lighting unit 13 secured on its upper roof 15. This unit has preferably a protective dome 17 that covers a very bright light source 19 therein which maybe a rotating light or any kind of warning light. The unit also has a GPS (Global Positioning Systems) antenna, generally indicated at 18 which receives satellite signals from GPS satellites and determines the location of the unit and the vehicle. Referring to Fig. 3, the unit is preferably a stand-alone unit with a housing 21 that is adapted to be mounted onto the roof of a vehicle. The dome 17 is of durable transparent material surrounding and protecting the high-intensity annunciator warning light system 19 supported on the housing 21. The flashing annunciator or warning light system 19 is similar to well-known warning or aircraft navigational lights, and may contain one or more incandescent bulbs or cluster of LEDs 22, or some other form of light source, often mounted on an assembly 24 that can rotate to enhance visibility of the lights 19. the light sources 19 are bright enough that they can be readily seen in low- visibility conditions by aircraft, and also the personnel in the airport tower from a substantial distance, e.g., 200 meters or more, or whatever distance may be required by FAA or local regulations. Normally the warning light source 13 includes electronics that cause the light sources 19 to strobe to further enhance visibility.

The housing 21 also supports the GPS antenna 18 and encloses additional circuitry therein, which will be discussed further below. The circuitry is connected by a power connection cable or cables 23 of conductors that connect to the vehicle battery electrical system and derive power for operation of the light and the control circuitry in the housing 21. The housing may also have an internal battery instead of or in addition to the connection 23 to the battery of the vehicle 11.

Referring to Fig. 4, the housing 21 supports thereon the annunciator warning light 19, and also encloses control circuitry electronics that operate the annunciator warning light 19 so that it is illuminated when the unit or the vehicle carrying the unit is on an aircraft operational area or runway, and so that the annunciator warning light 19 is deactivated when the unit 13 and the vehicle 11 is not on a runway.

The general structure of the electronics of the warning light unit 13 is illustrated in Fig. 4. The electronics includes control circuitry electronics 25 that is provided with electrical power from the vehicle battery or the vehicle electrical system, or potentially from a local battery power source within the housing 21 of the unit 13. This control circuitry 25 is connected with a global positioning system (GPS) receiver 27. The GPS receiver 27 is operatively connected to the GPS antenna 18 (see Fig. 3) and, as is well known in the art, receives GPS signals from GPS satellites, decodes the signals and derives from the signals longitude and latitude data indicating the precise location of the unit 13. The GPS system used is preferably a high resolution system, preferably a Wide Area Augmentation System (WAAS) enabled GPS system, which yields GPS data that is accurate to within as little as one meter of the location of the GPS receiver 27. This location data is transmitted as through the connection 28 to the control circuitry 25. The control circuitry 25 also is connected with a data storage device 29, which can be flash memory, a hard disk drive, some solid state memory of a different type, or virtually any type of data storage that is computer-accessible, i.e., accessible by the control circuitry 25. The data storage device 29 stores geographical information system (GIS) data defining the positions of the local aircraft operational areas, i.e., areas in the airport in which the unit is being used, in which, if an airport ground vehicle intrudes, it should have its annunciator warning light 19 activated. The areas are usually defined as polygonal boundaries, in which each vertex is a stored GIS data point. The coordinate system or references used in the GIS are preferably the same system, usually latitude and longitude, as the output of the GPS receiver used, so that comparison of the GPS location with the GIS map data does not involve conversion computations. The polygons are generally determined as slightly larger than the actual operational areas, to ensure that even if there is an error of a meter or more in the GPS readings, nonetheless, a vehicle carrying the unit 13 in an operational area will have its warning lights 19 activated.

To enhance the interchangeability of the unit 13 with various airports, and also to make local implementation easier wherever the unit 13 is employed, the GIS data preferably includes data defining the location of aircraft operational areas for a number of different airports in which the unit 13 might be installed, such as, e.g., all the airports in the United States or in the world. With that GIS data in data storage 29, the unit 13 may be installed on a vehicle and immediately used in any airport without modification. Alternatively, it is possible to program the GIS data by taking the unit on a vehicle and driving the perimeter of the restricted access areas on an airport with a local application active on the unit or on a connected computer that continually notes the GPS coordinates of the perimeter route and formulates from them the data defining the restricted areas in the GIS database, which is then stored in the memory, and may be loaded into other units brought into the system as well. Periodically and continually, the control circuitry 25 receives the GPS data defining the current location of the GPS receiver 27 and, based on the GPS data and the GIS data from the data storage device 29, the unit control circuitry 25 makes a determination whether the GPS receiver 27 (and, as a corollary, the unit 13 and the vehicle 11) is in a location that is classified as an aircraft operational area or not. A number of electronic or computer-implemented data-processing methods for making this determination can be employed, and these processes are well-known in the art of GPS data processing well-known in the art of GPS signal processing. The duty cycle of the GPS determination of the location can vary, but it should be short enough intervals that it is not possible for the vehicle to drive onto a restricted access area any significant distance without the GPS determining its location and lighting the warning light. GPS receivers exist that are fast enough to support a duty cycle of 4 Hz, and some GPS receivers could support a GPS duty cycle into the 10-20 Hz range. The unit of the preferred embodiment operates with a GPS duty cycle of in the range of 0.5 Hz to 3 Hz or faster, and particularly preferred is a GPS duty cycle of the GPS receiver identified herein of IHz, or 1 GPS location update / second.

Switch 31 is connected between the warning light 19 and its power supply, usually the link 23 to the vehicle battery or a local battery in the housing 21. This switch 31 can be in two positions:

OFF, in which the switch 31 interrupts the power to the warning light 19, and the warning light 19 is extinguished and dark, or ON, wherein the switch 31 causes power to be supplied through the switch 31 to warning light 19, in which case the warning light is activated, illuminating and performing its annunciator functions, i.e., flashing and rotating, or whatever the operation is for the particular warning light configuration. Responsive to a determination by the control circuitry 25 that the vehicle 11 and the unit 13 are in an aircraft operational area, the control circuitry 25 causes, e.g., by providing a high voltage at an input pin of switch 31, the switch 31 to turn to ON, sending the power to the warning light 19 and activating it. If the determination of the control circuitry 25 is that the unit 13 and the vehicle 11 are not on an aircraft operational area, then the control circuitry 25 does not cause the warning light to be switched on, e.g., sends no voltage to the input pin of switch 31, and the switch 31, which is biased to the OFF position, as a default setting, cuts the power to the warning light 19. This results in the warning light 19 being deactivated and extinguished responsive to that determination of the vehicle 11 not being on an aircraft operational area. Referring to Fig. 5, a more detailed schematic view of the unit electronics of Fig.

4 is shown.

The computational activity of the control circuitry is centered in a microprocessor, which takes the form, in the preferred embodiment, of Dios Pro 28 microcontroller 35, as sold by the company Kronos Robotics. The microcontroller 35 performs the necessary computerized calculations for operation of the warning light unit 13 pursuant to software instructions stored on SD flash memory card 37. The GIS data defining all the airports in a given region or country, e.g. all the airports in the United States, is also stored on SD memory card 37. In addition, the microcontroller 35 transmits and stores data of a log of system events, e.g., activation and deactivation of the warning light 19, as well as other location data logs, as will be discussed further below.

The GPS receiver 27 in the circuitry is in the form of a GPS receiver MN5010HS, a GPS receiver module manufactured by Micro Modular Technologies, Ltd. of Singapore (See www.micro-modular.com), which component is indicated at 39. The GPS receiver module 33 transmits its GPS-derived location data to microcontroller 35, where it is processed as discussed elsewhere herein. The GPS operation is enhanced by a GPS lock component 41, which generally operates as a buffer of GPS satellite data that allows the GPS receiver to remain "hot" at all times, without any lag time needed to accumulate added satellite signal data when the current GPS position is requested by the microcontroller 35. The power for the unit 13 is derived preferably from the battery of the vehicle 11, normally a 12 volt battery, indicated at 43. The battery 43 supplies power over lines 23 to a unit power switch 45 that turns the control circuitry on and off. When turned on, the power flows through to a voltage regulator generally indicated at 47, which converts the power to +3.3 volts DC and -3.3 volts DC, and supplies that current to the microcontroller 35 (that connection is not shown in Fig. 5). The power is preferably on all the time, as discussed elsewhere herein, to ensure that the vehicle warning light illuminates when the vehicle is on an airplane operational area, irrespective of whether the vehicle engine or electrical harness is on or off, or if the vehicle is being operated by a human or not. In the preferred embodiment, control of the warning light system 19 is accomplished by the microcontroller 35 communicating with LED Warning Light Controller 49. This component 49 is configured to control a warning light 19 in the form of LED arrays, and essentially can be directed to turn the light 19 on or off. The controller 49 can also control more elaborate operation of the light 19, e.g., flashing patters, rotation or non-rotation of the lights, and possibly some other capabilities of the warning light system employed, such as possibly elevating the light under certain circumstances. The commands for those actions are loaded with the software at system initialization. Generally, however, the primary command sent is activate or deactivate the warning light 19, i.e., the main command processing capability of the LED controller 49 includes the OFF and ON conditions, and it is in that sense the component corresponding to switch 31 of Fig. 4. The power to the light 19, as has been mentioned before, is supplied via a connection, not shown in Fig. 5, to the vehicle power system 43 that can be interrupted by switch 31, which is controlled by LED controller 49.

In addition, the LED controller 49 sends back status data that indicates whether the light is functioning properly or not. This data is in the form of a data signal that reflects a flag that is either yes (light operational) or no (malfunction). The unit communicates with a network at the airport installation using a Wi-Fi connection component 51, which is preferably a WiFIy GSX module, a low power Wi-Fi link. In addition, Bluetooth communication between the microcontroller 35 and any nearby Bluetooth enabled device by a Bluetooth communication link connected with microcontroller 35, via a Roving Networks, RN-41, or such as the Euzario BISM II Bluetooth Intelligent Serial Module.

Also, if the wireless communications become unworkable for whatever reason, the circuitry has an RS-232 transceiver 53 connected to a phone jack 54, or some other sort of hard-wired connection such as a USB socket, that allows a technician to plug into unit 13 and access the microcontroller 35 to program it or diagnose any issues of functionality.

The electronics comprise two other sensor components that are connected with the microcontroller 35.

A temperature sensor 57 is connected with, and transmits temperature data to, the microcontroller 35. GPS operations can be temperature sensitive, and the temperature therefore may be used to compensate for the effect of the local temperature on the calculation of the GPS position.

An accelerometer or motion detector 59 is attached to the microcontroller 35 and provides data indicative of the acceleration that the unit 13 is experiencing movement. Responsive to input from the accelerometer above a predetermined threshold, the microcontroller 35 initiates a GPS query to start determining any new position of the unit 13, as will be discussed further below.

Referring to Fig. 6, the operation of the unit 13, sometimes referred to as a FOGEL unit (Field Observable GIS Enabled Lighting), is illustrated by way of a flowchart.

At start-up 61 the unit initializes the wireless communications, which allow it to wirelessly receive commands from a central computer control system at the airport or from a nearby control system by Wi-Fi or Bluetooth, step 63. This interrupt is available at any time to override the ongoing operation of the unit 13. After this initialization, the microcontroller 35 enters into an infinite loop generally indicated at 65, whereby the microcontroller 35 repeatedly performs its various periodical tasks of monitoring the GPS and other sensors, and takes appropriate action in reaction to those inputs. If an interrupt by wireless communication occurs, the microcontroller 35 branches to the communications routine 63 to react, leaving the loop.

The microcontroller 35 first addresses any command found in its designated command memory area in step 67. If there is a command present, the microcontroller 35 proceeds to process the command, step 69. Commands are generally either commands to send data over the Wi-Fi network to the central computer system, or an internally- generated command to activate or deactivate the annunciator warning light. Commands to send data are processed by setting a flag that is checked each duty cycle. Commands to turn the lights on or off are processed by setting the appropriate output to the LED controller 49 from the microcontroller 35.

Other possible commands include a direct override command that would manually turn the lights on or off based on an operator command at a central control system. Commands might also require that data transmitted be in a particular selected format, e.g., in a human readable format, like Rich Data for a GPS tracking strip. A command may also be implemented that causes the unit 13 to simply confirm that its GPS receiver is still locked onto a satellite and the receiver is still listening to the satellite signals.

If there is no command, or after the command is processed, the microcontroller 35 in step 71 then examines any sensor buffers and determines if there is any data present. The buffers include primarily incoming position data of the GPS. The incoming data may also include data signals from the light controller 49, i.e., data indicating that the warning annunciator light has malfunctioned or that it is operational, or also data signals from the accelerometer or the temperature sensor. Also, a data flag may be produced if the battery power, either that of the vehicle 11 or a local internal battery, is low.

If any such data is present, the microcontroller 35 checks if the connection is available 73, and then sends the data or alert information (reporting light malfunction or low battery condition, for example) in step 75.

If there is no data or no connection, or if the requested data is sent as directed, the microcontroller 35 proceeds to check if the GPS data is available in step 77. If so, the microcontroller 35 collects and buffers the GPS data, step 79, applying a time stamp of the current time to it, and proceeds to analyze the data in step 81.

The data analysis results in a determination whether the GPS data indicates that the unit 13 is on an aircraft operational area or not. If there is a determination that the unit 13 is on an aircraft operational area, a command to activate the warning light 19 is placed in the command buffer, and the microcontroller 35 loops back up to run the cycle again, implementing the activate light command. If the determination is that the unit is not on an aircraft operational area, the command is cleared and the next duty cycle, the warning light command will be the default, i.e., to deactivate the warning annunciator light 19. The details of the data analysis step 81 are shown in flowchart form in Fig. 7.

First the microcontroller 35 waits for a data ready signal, step 83, and then it accesses the data that has been received, step 85. The data is checked for completeness in step 87, e.g., that all the expected fields of GPS data are present. The GPS data normally comprises 16 bytes, and if the data does not fit in such a field, the microcontroller 35 exits and restarts the loop. If the data is complete, the data is reviewed for validity, step 89, i.e., that the data supplied is within expected ranges, and does not contain clearly erroneous numerical information. If the data is incomplete, the microcontroller 35 exits and restarts the loop. If on the other hand the data is valid, the microcontroller 35 proceeds to check the GPS data against the GIS data stored in flash memory. The process for identifying the relevant runway is similar to any of the processes used by standard GPS systems to identify the location of the GPS device on an internally defined map defined by GIS data. This process of looking up the runway, step 91, identifies one or more runways near the location defined by the GPS data, and the runway (which is here intended to mean any aircraft operational area, including actual runways, where intrusion by the vehicle requires illumination of the annunciator warning light) is then compared to the current detected GPS location data and a determination is made (step 93) whether the runway is valid, i.e., whether the GPS location of the data is on the identified aircraft operational area or runway.

If the determination is yes, the location is on the runway, the microcontroller 35 activates the warning light 19, or, more precisely, stores a command in the command buffer directing that the light be turned on in step 95. This event is stored (step 97) in a tracking buffer or log, which is subsequently stored in the internal flash memory, and then output on demand to the central computer system. The microcontroller 35 then exits to the main loop, starting again at decision 67 of Fig. 6, and where it then processes the command (step 69) so as to turn on the light, in the preferred embodiment, by switching an output pin of the microcontroller 35 to high that causes the LED controller 49 to cut power to the warning light 19.

If the determination is no, that the GPS location is not on an aircraft operational area or runway, then no command to illuminate the light is placed in the command buffer, and the command buffer is kept empty, effectively deactivating the light 19 (step 96). Tracking buffers are then stored, step 98, as a log of the event, and the data analysis step is completed, with an exit 99 to the main loop of Fig. 6. When the command decision step 67 of the main loop seen in Fig. 6 is reached, the lack of the command to illuminate the light results in the relevant output pin of microcontroller 35 being dropped to low, its default condition. This results in controller 49 switching off the flow of power to the light 19, turning it off.

Referring to Fig. 8, the network environment of the vehicles carrying the warning lights of the invention is shown. A local area wireless network 100 is provided on the airport facility grounds. AU of the annunciator warning light units 101 on all the vehicles in the system, which may be a very large number are linked to this LAN 100 so as to send and receive data over the LAN 100. All units 101 are configured similarly to the above described annunciator warning light unit 13.

Central computer system 103 communicates over the LAN 100 with all of the units 101 and receives data from them, which it stores and processes. The central computer 103 includes operator interface devices 105, including as is well known, a display screen, a keyboard, a mouse, etc., and a software application running on the central computer allows the user there to administer the system by transmitting commands to the units 101 and reviewing or storing data sent back from the units.

The communications over the airport LAN 100 take place according to known network communications in which data is transferred as electronic data signals that correspond to packets according to a UDP packet protocol, each packet being organized according to an xml structure. Every unit 101 has its own unique device ID and address on the network. In addition, each of the various sensors in a unit, meaning the GPS receiver, the warning light status indicator, the temperature sensor, and the accelerometer, has its own unique respective sensor ID, so that data from the sensor can be specifically requested by the central computer 103 and, when a data packet is received from the sensor, the sensor sending the packet can be identified by its unique sensor ID in the data packet. In addition, the memory and all its GIS data is considered a sensor in this context, and it can be fully downloaded or overwritten by the central computer 105.

The units 101 can also be accessed via Bluetooth by a laptop or other mobile portable computer system 107 with Bluetooth capabilities. When the portable computer 107 is in Bluetooth range of one of the units 101, that unit 101 provides to the mobile system access to its data and processor so that it may be loaded with new data, or otherwise reprogrammed as desired. Diagnostics of the unit 101 may also be run by the mobile computer 107 through the Bluetooth connection. In general, the portable computer 107 operates according to a resident software application through which a user of the portable computer 107 can exercise all functions via the Bluetooth connection that the central computer 105 can perform via Wi-Fi over the LAN 100.

The central computer 103 can issue several types of commands to the units 101 at their unique network addresses these include a Capabilities Request, an Instant Data Request, and a Unit Info Request.

The Capabilities Request command object is typically used when the central computer 105 first loads and receives a sensor data from a device that it does not recognize. In response to the Capabilities Request, the unit 101 responds with a Device Capabilities xml object reporting the ID and attributes of the unit 101, including a definition of the xml version, the unit's unique ID, the unit's name and model, and an xml element of all the sensors on the unit 101. The Supported Sensors xml element is part of the Device Capabilities xml object, and it defines the different sensors on the unit 101 that are available for monitoring. The Supported Sensors element contains one or more Sensor Definition elements.

Each sensor definition element comprises for each sensor a packet of data that includes 1. a Sensor Unique ID (a name for the particular sensor that is unique over the entire network of units),

2. a reading type selected from possible types or readings including MEM (memory), LOC (location coordinates), ACC (acceleration), 3. display unit (units to be displayed to the user, e.g., latitude/longitude, bytes, acceleration),

4. the name of the reading to display to the user, generally the same as reading type, and

5. the format of the reading of the sensor (integer, string, floating decimal or Boolean, such as Go or NOGO)

The Instant Data Request object is used by the central computer 105 to receive readings at an interval of its choosing. An example of this would be if the central computer 105 user wants to monitor a unit in more detail, in which case central computer 105 would send an Instant Data Request once every couple of seconds. In response, the unit 101 sends a Reading Collection xml object to the central computer 105.

The Reading Collection xml object is the means by which the units 101 transmit readings to the central computer 105. Reading Collection xml objects are usually transmitted to the central computer 105 by all units 101 in operation at a predetermined user-selectable interval, e.g., every 3 minutes, selected via the interface application running on the central computer 105. They also may be requested by the Instant Data

Request command.

Reading Collection xml object contains the unit's unique ID, an identifier of the vehicle that the unit is attached to. The Reading Collection contains one or more Reading elements or xml objects, one for each sensor being reported, followed by any alerts from the unit, which are simple textual alerts reporting events, such as "WARNING LIGHT

ACTIVE".

Each Reading xml element contains the value of a sensor reading at a given point in time and it comprises the Sensor Unique ID, a timestamp, a flag for whether the reading is valid, i.e., an indication to the central computer 105 when there is a sensor malfunction, and the actual numerical reading itself. The Unit Info Request object is used to request a Unit Info object from a given unit. This type of request will normally be issued when the central computer 105 encounters a unit ID that it does not recognize. In response the unit 101 transmits back an xml object that identifies the unit and its attributes, including the unit ID ₃ the unit serial number, the type of GPS used by the unit the type of annunciator warning light on the unit, identification of the type of motion sensor or accelerometer, and the version of the unit or any attendant software.

Other commands that the central computer may allow the user to transmit to units 101 on the airport grounds are a manual override, which will selectively activate the warning light or extinguish it manually, or requests for Rich Data types, meaning request for a more detailed data log from the unit, such as a GPS tracking strip. Also, a command may request periodic acknowledgment that the GPS is still listening to a satellite, i.e., that the GPS is still locked to its current GPS satellite. This type of periodic acknowledgement system can reduce the power demands for the system.

Furthermore, the central computer system 105 provides the user with the capability of downloaded updates or modifications to the existing GIS data. This allows easy addition of e.g., a new runway, to the airport while maintaining the operating warning light system and network.

Units 101 enter into the network and access to them is assumed by the central computer 105 automatically.

A new unit 101 is powered on and associated with a vehicle. The unit begins transmitting Reading Collection objects over the LAN 100 to the central computer at an interval of its choosing. The central computer receives the Reading Collection object and determines that the unit's Unique ID is new, and it then sends a Capabilities Request to the unit. The unit receives the Capabilities Request and sends a Device Capabilities Object. The central computer receives and stores the Device Capabilities object. The unit is known to the system at this point. The unit then begins the normal process of sending periodic Reading Collection objects. The central computer receives, parses, and displays the Reading Collection data based upon the Device Capabilities for the unit. If the user requests more detailed information from the unit, it sends an Instant Data Request. The unit receives the Instant Data Request and sends a responsive Reading Collection object immediately. Normal operation of the unit continues in this way.

As a general rule, the central computer tracks movement of all the units by receiving GPS data from all of the units. The central computer 105 connects to the remote GIS monitoring system of the units over the LAN using a client connection that gives the central computer 105 program control over the connection and allows the server program to handle more than one unit. The central computer 105 program listens for unit communications, e.g., requests and responses, on a secondary port. By keeping this interface connectionless, setup overhead and associated timeouts can be avoided.

The unit GIS Location information is imported to the central computer 105 from the unit as a GIS xml file. This file information is read, converted, and stored in at the central computer as a converted GPS data xml file. The central computer imports the data from the microprocessor of the unit. However, the central computer will also be able to import GIS information directly from the GPS receiver as a sensor on the network. The GIS data received from the unit, converted and then stored at the central computer includes the following data: latitude in degrees north, longitude in degrees north, standard deviation of samples in meters, number of GPS fixes taken, time GPS receiver was on, in seconds, number of differential samples, horizontal dilution of precision, temperature of GPS receiver, and the status byte from a Garmin GPS receiver. This information is stored for each unit 101 in the network so that the central computer can at any point in time determine the location of the unit and its associated vehicle.

The annunciator warning light system of the invention works without any operator involvement, so that the warning light will illuminate automatically, even if the driver were to lose consciousness and allow the vehicle to drive onto a runway, or if the driver fell out of the vehicle and the vehicle was proceeding as a runaway vehicle on its own without a human operator.

Furthermore, the unit has a housing mounted on the vehicle and it is connected with the vehicle power supply, i.e., its battery. The vehicle electrical system, i.e., the battery, of the vehicle, is connected to the unit 13 such that power is supplied without interruption, regardless of whether the vehicle is turned on or not. Therefore, if a vehicle is left unattended on the runway with the engine turned off, it will nonetheless have its annunciator warning light flashing. Also, if a parked vehicle rolled on its own onto a runway, the warning light would illuminate.

Alternatively, the battery can be contained in the unit, so that the unit is fully self- contained, and can be placed on a vehicle without the need for an electrical connection, or the unit may even carried by a person without a vehicle involved.

Although the unit is here described as a separate add-on unit, a similar unit may be incorporated in a vehicle, not as a separate housing. Similarly, vehicles having existing warning lights may be retrofit with the GPS, data storage and other electronics of the unit so as to switch on the existing warning light only when received GIS/GPS data indicates that the vehicle has driven onto a runway, as described previously.

In addition, although this embodiment shows an airport, the inventions applicable to other environments where safety requires that a vehicle illuminate a warning light when in a certain area.

It will be understood that the terms and language used in this specification should be viewed as terms of description not of limitation, as those of skill in the art with this specification before them, will be able to make changes and modifications thereto without departing from the spirit of the invention.