Abstract: In some examples, a collision awareness system includes two cameras mounted on portions of a vehicle and processing circuitry configured to determine a position of an object based on an image captured by a first camera when the object is within a field of view of the first camera. The processing circuitry is further configured to determine the position of the object based on an image captured by a second camera when the object is within a field of view of the second camera. The processing circuitry is also configured to determine whether a distance between a future position of the vehicle and a current or future position of the object is less than a threshold level. In response to determine that the distance is less than the threshold level, the processing circuitry can generate an alert.

Abstract: Apparatuses for studying possible physical effects of dark matter may include an electronic oscillator. A power source may be in electrical communication with the electronic oscillator. An antenna may be in series electrical communication with the electronic oscillator. A first diode may be in series electrical communication with the electronic oscillator and the antenna. A second diode may be in series electrical communication with the electronic oscillator and the antenna. The first diode and the second diode may ensure and restrict flow of electrical current in one direction only in the antenna. Methods for studying possible physical effects of dark matter are also disclosed.

Abstract: An electromagnetic radiation source locating system including an electromagnetic radiation sensor including an antenna configured to detect a radiant energy transmission. A position detector is in communication with the controller and is configured to detect the position of the antenna relative to a reference coordinate system, while an orientation sensor is in communication with the controller and is configured to detect the orientation of the antenna and provide an orientation signal to the controller. A range sensor is configured to detect the distance to an aligned object in the path of a directional vector and provide a distance signal indicative thereof to the controller. An aerial vehicle may be in communication with the controller and configured to drop a marker for guiding navigators to the source of the radiant energy transmission.

Abstract: A system for displaying vertical weather information on an aviation display aboard an aircraft, the aircraft including an aircraft radar system for scanning a target, is provided. The system includes processing electronics configured to receive a target selection from a user input device, to receive an altitude value of an echo top of the target based on radar return data, and to cause the altitude value to be displayed on plan view of weather images on an aviation display in response to the received target selection.

Abstract: A location and guidance system including a flying craft and a reception device. The flying craft includes a plurality of antennas distributed around its fuselage and emitting rearwards with rectilinear polarization, the emitted signals being specific to each antenna, the positions and the dimensions of the antennas being configured such that the body of the flying craft avoids by masking for at least one antenna the reflections of the signal emitted by this antenna off the ground or off lateral obstacles whatever the position of the flying craft. The reception device is placed substantially on a trajectory axis of the flying craft and configured to be oriented to sight the rear thereof and includes at least two single-pulse antennas operating in orthogonal planes determines a position of the flying craft by analysing the emitted signals received by the antennas of the reception device.

Abstract: A device and method for three-dimensional positioning are provided. The three-dimensional positioning of a common reference point is determined by fusion of supplied measurements, taking into account a lever arm compensation between the reference point, a global navigation satellite system (GNSS) receiver antenna, at least one radar antenna, and an inertial measuring unit.

Abstract: Present novel and non-trivial system, device, and method for generating altitude data and/or height data are disclosed. A processor receives navigation data from an external source such as a global positioning system (“GPS”); receives navigation data from multiple internal sources; receives object data representative of terrain or surface feature elevation; determines an instant measurement of aircraft altitude as a function of these inputs; and generates aircraft altitude data responsive to such determination. In an additional embodiment, the processor receives reference point data representative of the elevation of the stationary reference point (e.g., a landing threshold point); determines an instant measurement of aircraft height as a function of this input and the instant measurement of aircraft altitude; and generates aircraft height data responsive to such determination.

Abstract: The invention relates to a monitoring device and method allowing surveillance of an aircraft in relation to aircraft and/or craft on an airport displacement zone. The invention is a system comprising a dedicated transmitter and receiver to receive the information regarding the location and displacement of the cooperative aircraft and to monitor the location of the said aircraft in relation to the cooperative aircraft. The monitoring application is based on the detection of conflict zones by inter-correlation of constraint surfaces of the airport zone. The invention applies to aircraft carrying communication moans for ADS-B networks for an airport zone monitoring application.

Abstract: A computer-implemented transportation information management system and method permits entry, recording, and transmission of operation and maintenance data related to FAA recordkeeping and recording requirements within an SQL database. A secure website permits entry and display of operation and maintenance data as well as facilitating data input using input devices such as a cellular telephone, a personal digital assistant, a personal computer, and a portable computer. The system outputs aircraft operation and maintenance data, automatic alerts of pilot flight and duty time limitations, and flight tracking and monitoring information via a spreadsheet, electronic mail message, text message, and a completed FAA mandatory reporting requirement forms to the aforementioned data input devices. Operation and maintenance data is automatically and continuously transferred to the FAA to populate FAA flight tracking data systems and air traffic control data system.

Abstract: A low visibility landing system is provided for guiding aircraft on landing approaches. The low visibility landing system may aid a pilot during landing in low visibility conditions such that an aircraft may descend to lower altitudes without visual contact with the runway than is possible with other landing systems. The system may use various navigational systems to produce a hybrid signal that may be more stable than individual signals of those navigational systems. The hybrid signal is compared to a predetermined landing approach plan to determine the deviation of the aircraft from the landing approach plan and to provide guidance to the pilot to get the aircraft back onto the landing approach plan. The system may also use multiple navigational systems to perform checks on an operation of a primary navigational system to ensure that the primary navigational system is operating accurately.

Abstract: Present novel and non-trivial system, device, and method for generating altitude data and/or height data are disclosed. A processor receives navigation data from an external source such as a global positioning system (“GPS”); receives navigation data from multiple internal sources; receives object data representative of terrain or surface feature elevation; determines an instant measurement of aircraft altitude as a function of these inputs; and generates aircraft altitude data responsive to such determination. In an additional embodiment, the processor receives reference point data representative of the elevation of the stationary reference point (e.g., a landing threshold point); determines an instant measurement of aircraft height as a function of this input and the instant measurement of aircraft altitude; and generates aircraft height data responsive to such determination.

Abstract: A multilateration system and method includes a plurality of receiver stations for receiving signals from an aircraft, and a controller that derives the position of the aircraft by applying a multilateration process to outputs from the receiver stations. For this purpose, the controller determines the altitude of the aircraft and selects a multilateration process that is to be used for position determination, based on the determined altitude.

Abstract: In one aspect, a method includes sending an interrogation request using an omni-directional antenna at a secondary surveillance radar, receiving, from responding aircraft, interrogation responses comprising identity and altitude, determining a distance to each of the responding aircraft based on a time the interrogation request was sent and a time an interrogation response was received, receiving, from a primary radar, positions of tracks, correlating the distances of each responding aircraft with the positions of the tracks to form a set of candidates by position; and sending identity, altitude and position of a track if there is one candidate from the set of candidates.

Abstract: A multilateration system and method includes a plurality of receiver stations for receiving signals from an aircraft, and a controller that derives the position of the aircraft by applying a multilateration process to outputs from the receiver stations. For this purpose, the controller determines the altitude of the aircraft and selects a multilateration process that is to be used for position determination, based on the determined altitude.

Abstract: A multilateration system and method includes a plurality of receiver stations for receiving signals from an aircraft, and a controller that derives the position of the aircraft by applying a multilateration process to outputs from the receiver stations. For this purpose, the controller determines the altitude of the aircraft and selects a multilateration process that is to be used for position determination, based on the determined altitude.

Abstract: A precision radar registration (PR2) system and method that employs highly accurate geo-referenced positional data as a basis for correcting registration bias present in radar data. In one embodiment, the PR2 method includes sample collection and bias computation function processes. The sample collection process includes ADS-B sample collection, radar sample collection, and time alignment sub-processes. The bias computation function process includes bias computation, quality monitoring and non-linear effects monitoring sub-processes. The bias computation sub-process results in a bias correction solution including range bias b?, azimuth bias b?, and time bias bT parameters. The quality monitoring sub-process results in an estimate of solution quality. The non-linear effects monitoring sub-process results in detection of the presence of non-linear bias, if any, in the bias correction solution.

Abstract: Methods and apparatus for an ADS-B system having a single link for communication and/or ADS-B/Mode-S coordination. With this arrangement, the system communication is efficiently used.

Abstract: The present invention relates to a method for determining the position notably the elevation of a target flying at very low altitude. An electromagnetic detection system extracts the measurement of the elevation on the basis of the amplitude of the interference signal produced by a signal emitted directly by the target and by a signal emitted by the target towards the ground then reflected by the ground towards the radar. Embodiments of the invention can notably be used within the framework of the guidance of drones in the final landing phase.

Abstract: A method (400), a system and a computer program product are disclosed for graphically displaying air traffic control information in an air traffic control system. Information about objects in an air traffic control environment is compiled and calculated (410). Tokens (e.g., text, icons, images, or other symbols) corresponding to the objects in the air traffic control environment are displayed (420). At least two objects are selectively designated (430) in combination as a source object and a target object connected by a bearing and range line token (210, 220, 230, 240). Air traffic control information (212, 222, 232, 242) about the combination of objects associated with the bearing and range line token dependent upon the combination of objects designated in the combination is displayed (440). The displayed air traffic control information is required decision making information to enable an air traffic controller to manage air traffic.

Abstract: Navigation of an aircraft is facilitated through the displaying on a map of an over flown region, and of the limits of zones within range of the aircraft in an emergency situation. The points of the zones within range of the aircraft are tagged on the basis of: an estimate of the vertical margins to reach these points, taking into account non-maneuverability zones neighboring the aircraft to be circumvented; a vertical flight profile to be complied with; and a safety height margin.

Abstract: A device and method for detecting air turbulence determine a theoretical height corresponding to the difference between an extrapolated height of an isentropic trajectory and the current height of an aircraft. This theoretical height is compared with a height threshold indicating a risk of turbulence.

Abstract: A transmitter (13) operates in an immediate scan after an initial acquisition or detection of an altered aircraft ID by a changed flight status, to transmit to an aircraft a sequence of interrogation signals requesting an aircraft ID transmission, a verifier (17) operates upon acquisition of a reply signal including an aircraft ID transmitted from a transponder on the aircraft, to store in a memory (17a) a mode S address assigned to the aircraft and the aircraft ID in an associating manner, and upon an occurrence of a storage of aircraft IDs associated with the mode S address in the memory (17a), to determine whether or not the aircraft ID is correct, depending on whether or not the aircraft IDs have a match therein, and a report generator (18) operates upon a determination for the aircraft ID to be correct, to prepare a target report using the aircraft ID.

Abstract: An air traffic control system, for use by a controller controlling a plurality of aircraft held vertically separated in a stack, the system comprising at least one processor; a display device for the control generating a display controlled by said at least one processor, and at least one device for selectively receiving, from said aircraft, an indication of their intended future altitudes; in which said processor is arranged to receive such intended altitude data; to compare said intended altitude data with current altitude and/or intended altitude data of other aircraft; and to generate said display on said display device so as to list said plurality of aircraft, to highlight a first part of the display relating to a first aircraft whose intended altitude overlaps with the current or intended altitude of at least one said second aircraft, and to highlight also a second part of the display relating to said second aircraft.

Abstract: The present invention relates to a method for determining the position notably the elevation of a target flying at very low altitude. An electromagnetic detection system extracts the measurement of the elevation on the basis of the amplitude of the interference signal produced by a signal emitted directly by the target and by a signal emitted by the target towards the ground then reflected by the ground towards the radar. Embodiments of the invention can notably be used within the framework of the guidance of drones in the final landing phase.

Abstract: In the described system the multilateration process to be applied to determine an aircraft's position is chosen on the basis of the available returns, receiver geometry and the height of the aircraft.

Abstract: Disclosed is a Mode S radar which specifies an aircraft by transmitting interrogations to an aircraft A equipped with a Mode S transponder, and by then receiving and decoding replies corresponding to these interrogations. In the Mode S radar, detection reports on the aircraft A are generated in a manner that: for a Mode A code necessary for generating detection reports, when identicalness between the Mode A codes obtained in a plurality of scans after the initial acquisition of the aircraft A has been found to exist, the Mode A code thus found identical is adopted without carrying out a Mode A code interrogation (UF=5) thereafter. Accordingly, the Mode S secondary surveillance capable of generating more highly reliable detection reports is achieved.

Abstract: The device (1) comprises a radar (2) which is able to detect any nearby aircraft and means (7) for presenting to a pilot an indication indicating, as appropriate, such a detection.

Abstract: The present invention is directed to a traffic display for an aircraft, which includes a vertical traffic indicator. The vertical traffic indicator includes flight levels, depicted utilizing differing visual patterns to represent the current flight level as well as available and unavailable flight levels for transit. The vertical traffic indicator includes aircraft indicators positioned in relation to flight levels to indicate attitude. The aircraft indicators may also include status indicators indicating separation standards, vertical trend, intent, or whether an aircraft is a reference aircraft for an ITP. The traffic display provides clear and intuitive means of understanding the flying environment related to the performance of the ITP, increasing situational awareness and simplifying the ITP. The traffic display is specifically advantageous for performance of an ITP, but may be integrated with displays including terrain, weather, flight plan waypoints, or TCAS (Traffic Collision Avoidance System) traffic.

Abstract: Disclosed is a Mode S radar which specifies an aircraft by transmitting interrogations to an aircraft A equipped with a Mode S transponder, and by then receiving and decoding replies corresponding to these interrogations. In the Mode S radar, detection reports on the aircraft A are generated in a manner that: for a Mode A code necessary for generating detection reports, when identicalness between the Mode A codes obtained in a plurality of scans after the initial acquisition of the aircraft A has been found to exist, the Mode A code thus found identical is adopted without carrying out a Mode A code interrogation (UF=5) thereafter. Accordingly, the Mode S secondary surveillance capable of generating more highly reliable detection reports is achieved.

Abstract: In a DME ground apparatus, under the control of a transmission-rate monitoring control unit, the transponder unit decodes an interrogation signal it has received and generates a response signal. The transmission rate at which to transmit the response signal is monitored. If the result of the monitoring indicates that the transmission rate has reached a preset value, the response signal is transmitted from the DME ground apparatus. If the result of the monitoring indicates that the transmission rate has not reached a preset value, squitter pulses are transmitted from the DME ground apparatus.

Abstract: A system is for recognizing obstructions and monitoring movements on or above an airport area (1) with sensors (2, 3, 4). A sensor (2) is a radar device having a plurality of antenna elements (12, 14), which are affixed to a curved surface (15) of an antenna carrier (2a) and are turned on, one after the other, in terms of time. Thus a first part of the antenna elements (14) is disposed on a first circular line (13) on the surface of the antenna carrier (2a), and a second part of the antenna elements (12) is disposed on a circular line (15) perpendicular to the first circular line (13). Therefore the data of the radar device (2) are evaluated in a first ROSAR process, to image the situation on the ground, and in a second ROSAR process, to image the heights of the flying objects to be observed.

Abstract: A method for display of radar data includes performing a first radar scan to obtain, for at least one object (24), a first range reading, a first azimuth reading, and a first altitude reading. A second radar scan is then performed to obtain, for the at least one object (24), a second range reading, a second azimuth reading, and a second altitude reading. Position and travel direction of the at least one object (24) are computed within a predetermined cylindrical volume (20), according to readings from the first and second radar scans. An icon (34) is assigned to the at least one object (24). A reference point (R) is determined for the predetermined cylindrical volume. The icon (34) is then displayed within the predetermined cylindrical volume (20) in stereoscopic form.

Abstract: A ground-based CFIT warning system provides pilots with CFIT alerts. The system is based upon a ground-based tracking system, which provides surveillance of aircraft, such as the AirScene™ multilateration system manufactured by Rannoch Corporation of Alexandria, Va. The system monitors both horizontal and vertical positions of aircraft. When an aircraft has been determined to be operating below safe altitudes, or too close to obstructions, the pilot is provided with a warning. The warning may be delivered via the pilot's voice communications and/or a data link or the like.

Abstract: A system and method for determining the vertical integrity of an altitude component of an aircraft navigational signal through the use of a receiver-autonomous vertical integrity monitoring (RAVIM) algorithm. The system and methods also provide timely warning to vehicle operators if the integrity of the signal is unacceptable or unknown. The system and methods are capable of determining the vertical integrity of an incoming signal without relying upon data embedded within the incoming signal itself. In addition, the system and methods of the present invention provide vertical integrity to vehicle operators in instances, such as when the specific aircraft navigational signal is not operating, when the specific aircraft navigational signal is not available in a particular region, or when an aircraft is operating outside the geographic area covered by the specific aircraft navigational signal system.

Abstract: A process and apparatus are disclosed for estimating changes in the vertical mode of flight of an aircraft. The process and apparatus utilize a vertical motion detection method (VMD) and a modified altitude post processor logic to reduce the time delay for determination of vertical mode of flight changes.

Abstract: A computer generated pilot instruction system for providing spatial information to a pilot corresponding to the difference between the actual landing fight path and optimal landing flight path.

Abstract: A system for determining an altitude of an aircraft using barometric pressure measurements is disclosed comprising: a transmitter disposed at a ground station for transmitting a signal to the aircraft, which signal including first data representative of barometric pressure at the ground station; a receiver disposed at the aircraft for receiving the transmitted signal; sensing apparatus disposed at the aircraft for measuring barometric pressure at the altitude of the aircraft and generating second data representative thereof; and processing circuitry for determining the altitude of the aircraft based on the first and second data and data representative of the elevation of the ground station. The ground station includes sensing apparatus for measuring barometric pressure at the ground station and generating pressure data representative thereof which is superimposed onto a carrier signal of the transmitter for transmission to the aircraft.

Abstract: System and methods for a ground based millimeter wave imaging system that provides real-time millimeter wave images of an airport to one or more aircraft from one or more ground stations (18). The system includes at least one millimeter wave transceiver (19) that is located in each one or more ground stations. Each at least one millimeter wave transceiver collects real-time millimeter wave images of the airport. At least one image processor (21) is operatively connected to the at least one millimeter wave transceiver, and processes the real-time millimeter wave images of the airport. At least one data link (22) allows communication of information between the one or more aircraft and the one or more ground station. The one or more ground stations transmit the processed realtime millimeter wave images to the one or more aircraft using the at least one link.

Abstract: A system and method for improving the accuracy of altitude determinations in an inertial navigation system. Pressure measurements available to the inertial navigation system are used to initially calculate an estimated pressure altitude using the standard day model for the atmosphere. Temperature measurements are further utilized in the physical relationship between temperature, pressure, and altitude to compute a second computed altitude. A change between subsequent second computed altitudes is calculated and compared with a respective change in the computed pressure altitude in order to generate a correction value. The correction value is then used to modify the computed pressure altitude to generate a more accurate determination of the absolute altitude of the inertial navigation system.

Abstract: The apparatus of the present invention uses radar altimeter measurements and stored terrain altitude profiles to provide pre-filtered observations to a Kalman filter for estimating barometric offset at the airport runway, and barometric scale factor for offsets above the runway. These offsets are used with the smoothed baro-inertial output from an inertial reference system to provide 3 dimensional constant rate of descent approach procedures to replace non-precision approach procedures based on constant barometric altitude step approaches. The horizontal positions used as reference for the stored terrain altitude profiles are obtained from a prior art navigation apparatus. The integrity of all measurements is assured by using long term averages of the Kalman filter residuals to detect failures. In addition, the estimated baro offset at the runway is compared for consistency with the baro offset obtained by the pilot from the airport by radio.

Abstract: The present automated vehicle travel path determination system which computes a travel path for a vehicle from an origination point to a destination point based on the operating characteristics of the vehicle as well as phenomena extant in the multidimensional space, which phenomena have an impact on the cost of operation of the vehicle. This vehicle travel path determination system can concurrently consider a plurality of vehicle operating characteristics in selecting the travel path. The travel path is optimized for a weighted selection of a number of cost factors, which weighted selection represents a desired combination of cost factors for the operation of this particular vehicle. This vehicle travel path determination system also considers the time varying nature of the phenomena that exist within the multidimensional space and the impact these time varying phenomena have on the vehicle as it traverses the travel path.

Abstract: A method for calibrating a pressure-sensing altitude sensor of an aircraft while the aircraft is in flight. The method includes the steps of obtaining a set of reference atmospheric pressures as a function of height above a base station by affixing a reference pressure sensor to a balloon. As the balloon is released into the atmosphere, the reference sensor continuously measures the atmospheric pressures and transmits the data back to the base station while a ground-based radar disposed adjacent the base station measures the height of the balloon. An aircraft flying in a vicinity of the base station can calibrate its pressure-sensing altitude sensors by measuring the atmospheric pressure outside the aircraft and its geometric height relative to the base station and then comparing the pressure measurements with corresponding reference pressure values at a geometric height that is substantially that same as the geometric height of the aircraft.

Abstract: An aircraft N-number control system includes a receiver for receiving aircraft identification information signals representing alphanumeric characters corresponding to an aircraft. A microprocessor operating in accordance with stored programming instructions processes the received aircraft identification information signals into alphanumeric codes, determines whether there is a substantial similarity between the alphanumeric codes representing two aircraft and generates an output signal representing the alphanumeric codes only if there is no substantial similarity. The alphanumeric codes representing the aircraft are displayed on a air traffic controller's radar screen in response to the output signal.

Abstract: Apparatus for rejecting multipath reply signals received from a target transponder within a selectable time period, comprising: a top antenna and a bottom antenna to detect reply signals; means for determining an altitude code associated with each reply signal detected by the antennas respectively; means for determining a differential time of arrival (DTA) value for each reply signal detected by the antennas respectively; and processing means for: 1) producing, for each top antenna reply signal, a top antenna target report that includes the altitude code and DTA values; 2) producing for each bottom antenna reply signal, a bottom antenna target report that includes the altitude code and DTA data; and 3) comparing each top antenna report data with corresponding data from each bottom antenna report, and marking out each bottom antenna report that is a multipath reply based on such comparison.

Abstract: Systems are provided to derive a value of barometric pressure at a defined location in the atmosphere at a computed geometric height. By using the geometric height in a look-up table of pressure/height values representing a standard atmospheric profile, atmospheric deviation data indicative of the difference between measured and reference pressures at that atmospheric location (C) is derived. Ground-based interrogators (10,20) located at spaced positions are used to initiate response signals from airborne transponders commonly installed in transient aircraft (C). Using resulting range data based on round-trip timing differences in signals sent to (12,16) and received from (16,14) the airborne transponder (C), geometric analysis and computation is used (18) to determine the geometric height of the transponder representing a specific atmospheric location.

Abstract: Conventional secondary radar systems use mechanically rotating antennas to radiate a concentrated beam that rotates in a horizontal plane. Data exchange between ground stations and airborne transponders can only take place if the aircraft is struck by the antenna lobe. The distance from the aircraft to the ground station is determined from the signal transit time. Directional information is derived from the antenna position. The secondary radar system according to the invention uses an omnidirectional antenna, so that data can be exchanged between ground station and aircraft at any time. To determine the position of the aircraft, interrogation signals are transmitted by a single active ground station such that the reply signal from a transponder falls within the common system time frame of the ground station. The times of arrival of the reply signals at different ground stations are then directly proportional to the distances from the aircraft to these ground stations.

Abstract: A method of processing a plurality of tracks representative of one or more target aircraft in a vicinity of a surveillance aircraft, where each track is generated in response to target reply signals provided by the target aircraft in response to interrogation signals transmitted by the surveillance aircraft, includes eliminating a portion of the plurality of tracks which are duplicate tracks of the same target aircraft. The remaining tracks are maintained and updated in response to the target reply signals provided by the target aircraft. A threat level for each of the remaining tracks is determined and two or more of the remaining tracks which are possibly representative of a same target aircraft are merged resulting in a composite track. The composite track is output to a display device utilizing information from a particular remaining track of the composite track having the greatest threat level to the surveillance aircraft while continuing to maintain and update all the remaining tracks.

Abstract: A collision warning signal for at least one vehicle is provided by transmitting from the surface of the earth a radio signal, receiving at the surface of the earth, a radio signal returned by a vehicle in response to the transmitted radio signal, determining an elapsed time between the transmitting of the radio signal and the receiving of the corresponding returned radio signal, determining the position of the vehicle at least in part in dependence upon the determined elapsed time, comparing the determined position of the vehicle with terrain data stored in a data base, and generating a warning signal based on the comparison if predetermined parameters are satisfied.

Abstract: The present invention is directed to a Mode S uplink or interrogation signal demodulation system which can quickly recognize the Mode S signal and also filter out of noise present in the Mode S uplink or interrogation signal, thereby reducing the bit error rate. To realize this goal the present invention includes a digital differential phase-shift keyed demodulator to demodulate the differential phase-shift keyed data, thereby reducing the time needed to acquire the Mode S uplink or interrogation signal. This digital demodulator also reduces the noise present in the Mode S uplink or interrogation signal and provides an integrated system which is small in structure that can be easily implemented in an aircraft. This Mode S system also includes a preamble and sync phase reversal detection circuit to recognize if the transmitted signal is a Mode S signal. This signal also utilizes Mode A and Mode C detection devices to make the system compatible with present communication systems.

Abstract: The apparatus of the present invention uses radar altimeter measurements and stored terrain altitude profiles to provide pre-filtered observations to a Kalman filter for estimating barometric offset at the airport runway, and barometric scale factor for offsets above the runway. These offsets are used with the smoothed baro-inertial output from an inertial reference system to provide 3 dimensional constant rate of descent approach procedures to replace non-precision approach procedures based on constant barometric altitude step approaches. The horizontal positions used as reference for the stored terrain altitude profiles are obtained from a prior art navigation apparatus. The integrity of all measurements is assured by using long term averages of the Kalman filter residuals to detect failures. In addition, the estimated baro offset at the runway is compared for consistency with the baro offset obtained by the pilot from the airport by radio.