U.S. patent application number 14/669143 was filed with the patent office on 2016-09-29 for aircraft synthetic vision systems utilizing data from local area augmentation systems, and methods for operating such aircraft synthetic vision systems.
This patent application is currently assigned to HONEYWELL INTERNATIONAL INC.. The applicant listed for this patent is HONEYWELL INTERNATIONAL INC.. Invention is credited to Lin Du, Guoqing Wang, Bin Zhang.
Application Number | 20160282120 14/669143 |
Document ID | / |
Family ID | 55589723 |
Filed Date | 2016-09-29 |
United States Patent
Application |
20160282120 |
Kind Code |
A1 |
Wang; Guoqing ; et
al. |
September 29, 2016 |
AIRCRAFT SYNTHETIC VISION SYSTEMS UTILIZING DATA FROM LOCAL AREA
AUGMENTATION SYSTEMS, AND METHODS FOR OPERATING SUCH AIRCRAFT
SYNTHETIC VISION SYSTEMS
Abstract
An aircraft synthetic vision display system (SVS) includes a
topographical database including topographical information relating
to an airport, a global positioning system receiver that receives a
satellite signal from a global positioning satellite to determine a
geographical position of the aircraft, and a ground-based
augmentation system receiver that receives a ground-based signal
from a ground-based transmitter associated with the airport,
wherein the ground-based signal includes geographical information
associated with the airport. The SVS further includes a computer
processor that retrieves the topographical information from the
topographical database based on the geographical position of the
aircraft, that retrieves the geographical information associated
with the airport, and that corrects the topographical information
using the geographical information associated with the airport to
generate corrected topographical information. Still further, the
SVS includes a display device that renders three-dimensional
synthetic imagery of environs of the aircraft based on the
corrected topographical information.
Inventors: |
Wang; Guoqing; (Beijing,
CN) ; Zhang; Bin; (Beijing, CN) ; Du; Lin;
(Beijing, CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HONEYWELL INTERNATIONAL INC. |
Morristown |
NJ |
US |
|
|
Assignee: |
HONEYWELL INTERNATIONAL
INC.
Morristown
NJ
|
Family ID: |
55589723 |
Appl. No.: |
14/669143 |
Filed: |
March 26, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01C 21/20 20130101;
G01C 23/00 20130101; G08G 5/025 20130101; G08G 5/0078 20130101;
G08G 5/0086 20130101; G08G 5/0021 20130101; G01C 21/005 20130101;
G01S 19/42 20130101; G08G 5/0013 20130101 |
International
Class: |
G01C 21/00 20060101
G01C021/00; G01S 19/42 20060101 G01S019/42; G08G 5/00 20060101
G08G005/00; G01C 21/20 20060101 G01C021/20; G01C 23/00 20060101
G01C023/00 |
Claims
1. An aircraft synthetic vision display system comprising: a
topographical database comprising topographical information
relating to an airport; a global positioning system receiver that
receives a satellite signal from a global positioning satellite to
determine a geographical position of the aircraft; a ground-based
augmentation system receiver that receives a ground-based signal
from a ground-based transmitter associated with the airport,
wherein the ground-based augmentation system receiver receives the
ground-based signal from a local area augmentation system
associated with the airport, wherein the ground-based signal
comprises a very-high frequency data broadcast (VDB) signal,
wherein the VDB signal comprises: geographical information
associated with the airport, message Type 4 information comprising
final approach segment information associated with an approach to a
runway at the airport, and runway occupancy status information; a
computer processor that retrieves the topographical information
from the topographical database based on the geographical position
of the aircraft, that retrieves the geographical information
associated with the airport, that validates the topographical
information using the geographical information associated with the
airport, and that corrects the topographical information using the
geographical information associated with the airport to generate
corrected topographical information; and a display device that
renders three-dimensional synthetic imagery of environs of the
aircraft based on the corrected topographical information, the
three-dimensional synthetic imagery further comprising a graphical
rendering of the runway at the airport, the final approach segment
based on the message Type 4 information, and an aircraft symbol on
the runway based on the runway occupancy status information.
2. The system of claim 1, wherein the topographical database
comprises a terrain database that comprises terrain information
associated with the airport.
3. The system of claim 1, wherein the topographical database
comprises a navigation database that comprises navigational
information for navigational routing and procedures associated with
the airport.
4. The system of claim 1, wherein the topographical database
comprises a runway database that comprises runway information
associated with the airport.
5. The system of claim 1, wherein the topographical database
comprises an obstacle database that comprises obstacle information
concerning obstacles in the vicinity of the airport.
6. The system of claim 1, wherein a multi-mode receiver comprises
the global positioning system receiver and the ground-based
augmentation system receiver.
7. (canceled)
8. (canceled)
9. The system of claim 1, wherein the topographical information
comprises an error or a bias that causes a feature of the airport
to be indicated at a geographical location other than its true
geographical location.
10. (canceled)
11. A method of operating a synthetic vision system of an aircraft
comprising the steps of: receiving a satellite signal from a global
positioning satellite to determine a geographical position of the
aircraft; receiving a ground-based signal from a ground-based
transmitter associated with the airport, wherein the ground-based
signal comprises a very-high frequency data broadcast (VDB) signal,
wherein the VDB signal comprises: geographical information
associated with the airport, message Type 4 information comprising
final approach segment information associated with an approach to a
runway at the airport, and runway occupancy status information;
using a computer processor: retrieving topographical information
from based on the geographical position of the aircraft, retrieving
the geographical information associated with the airport,
validating the topographical information using the geographical
information associated with the airport, and correcting the
topographical information using the geographical information
associated with the airport to generate corrected topographical
information; and rendering three-dimensional synthetic imagery of
environs of the aircraft based on the corrected topographical
information, the three-dimensional synthetic imagery further
comprising a geographical rendering of the runway at the airport,
the final approach segment based on the message Type 4 information,
and an aircraft symbol on the runway based on the runway occupancy
status information.
12. The method of claim 11, wherein receiving topographical
information comprises receiving terrain information associated with
the airport.
13. The method of claim 11, wherein receiving topographical
information comprises receiving navigational information for
navigational routing and procedures associated with the
airport.
14. (canceled)
15. The method of claim 11, wherein receiving topographical
information comprises receiving obstacle information concerning
obstacles in the vicinity of the airport.
16. (canceled)
17. (canceled)
18. The method of claim 11, wherein receiving the topographical
information comprises receiving topographical information that
comprises an error or a bias that causes a feature of the airport
to be indicated at a geographical location other than its true
geographical location.
19. (canceled)
20. An aircraft synthetic vision display system comprising: a
plurality of topographical database comprising topographical
information relating to an airport, wherein the plurality of
topographical databases comprise at least a terrain database that
comprises terrain information associated with the airport, a
navigation database that comprises navigational information for
navigational routing and procedures associated with the airport, a
runway database that comprises runway information associated with
the airport, and an obstacle database that comprises obstacle
information concerning obstacles in the vicinity of the airport,
and wherein the topographical information comprises an error or
bias that causes a feature of the airport to be indicated at a
geographical location other than its true geographical location. a
multi-mode receiver comprising a plurality of receiver
functionalities comprising at least a global positioning system
receiver that receives a satellite signal from a global positioning
satellite to determine a geographical position of the aircraft and
a very-high frequency data broadcast receiver that receives a
ground-based signal from a local area augmentation system
transmitter associated with the airport, wherein the ground-based
signal comprises a Type 4 message including geographical
information associated with the airport that comprises final
approach segment geographical information pertaining to a runway of
the airport and runway occupancy status information; a computer
processor that retrieves the topographical information from the
topographical database based on the geographical position of the
aircraft, that retrieves the geographical information associated
with the airport, that validates the topographical information
using the geographical information associated with the airport, and
that corrects the topographical information using the geographical
information associated with the airport to generate corrected
topographical information; and a display device that renders
three-dimensional synthetic imagery of environs of the aircraft
based on the corrected topographical information, wherein the
three-dimensional synthetic imagery comprises a graphical rendering
of at least the runway of the airport, the final approach segment
based on the message Type 4 information, and an aircraft symbol on
the runway based on the runway occupancy status information.
21. The synthetic vision display system of claim 20, wherein the
VDB signal further comprises runway hold short information, and
wherein the three-dimensional synthetic imagery comprises a
graphical rendering of the runway hold short information on the
runway as a graphical bar on the runway.
22. The synthetic vision display system of claim 21, wherein the
VDB signal further comprises runway closure Notice to Airmen
(NOTAM) information, and wherein the three-dimensional synthetic
imagery comprises textual indication of the runway closure NOTAM.
Description
TECHNICAL FIELD
[0001] The present disclosure generally relates to aircraft display
systems and methods for operating aircraft display systems. More
particularly, the present disclosure relates to aircraft synthetic
vision systems that utilize data from local area augmentation
systems, and methods for operating such aircraft synthetic vision
systems.
BACKGROUND
[0002] Many aircraft are equipped with one or more vision enhancing
systems. Such vision enhancing systems are designed and configured
to assist a pilot when flying in conditions that diminish the view
from the cockpit. One example of a vision enhancing system is known
as a synthetic vision system (hereinafter, "SVS"). A typical SVS is
configured to work in conjunction with a position determining unit
associated with the aircraft as well as dynamic sensors that sense
aircraft altitude, heading, and orientation. The SVS includes or
accesses a database containing information relating to the
topography along the aircraft's flight path, such as information
relating to the terrain and known man-made and natural obstacles
proximate the aircraft flight path. The SVS receives inputs from
the position determining unit indicative of the aircraft location
and also receives inputs from the dynamic sensors. The SVS is
configured to utilize the position, heading, altitude, and
orientation information and the topographical information contained
in the database, and generate a three-dimensional image that shows
the topographical environment through which the aircraft is flying
from the perspective of a person sitting in the cockpit of the
aircraft. The three-dimensional image (also referred to herein as
an "SVS image") may be displayed to the pilot on any suitable
display unit accessible to the pilot. The SVS image includes
features that are graphically rendered including, without
limitation, a synthetic perspective view of terrain and obstacles
located proximate the aircraft's flight path. Using a SVS, the
pilot can look at a display screen of the display unit to gain an
understanding of the three-dimensional topographical environment
through which the aircraft is flying and can also see what lies
ahead. The pilot can also look at the display screen to determine
aircraft proximity to one or more obstacles proximate the flight
path.
[0003] The approach to landing and touch down on the runway of an
aircraft is probably the most challenging task a pilot undertakes
during normal operation. To perform the landing properly, the
aircraft approaches the runway within an envelope of attitude,
course, speed, and rate of descent limits. The course limits
include, for example, both lateral limits and glide slope limits.
In some instances visibility may be poor during approach and
landing operations, resulting in what is known as instrument flight
conditions. During instrument flight conditions, pilots rely on
instruments, rather than visual references, to navigate the
aircraft. Even during good weather conditions, pilots typically
rely on instruments to some extent during the approach. Some SVS
systems known in the art have been developed to supplement the
pilot's reliance on instruments. For example, these systems allow
pilots to descend to a low altitude, e.g., to 150 feet above the
runway, using a combination of databases, advanced symbology,
altimetry error detection, and high precision augmented
coordinates. These systems utilize a wide area augmentation system
(WAAS) GPS navigation aid, a flight management system, and an
inertial navigation system to dynamically calibrate and determine a
precise approach course to a runway and display the approach course
relative to the runway centerline direction to pilots using the
SVS.
[0004] The usefulness of these SVS systems for approach and landing
is limited, however, by the accuracy of the topographical database,
particularly in the terminal area of the airport. It has been
discovered, for example, that in some instances, published terminal
area topographical data may include unintended errors or biases in
relation to the geographic position of certain features, such as
runways, obstacles, etc. If these errors or biases are then
introduced into the SVS topographical databases, then the 3-D
rendered images presented to the pilot on the SVS may not match the
aircraft's actual environment, which is problematic in the context
of flying a precision approach to the airport supplemented by the
SVS.
[0005] Accordingly, it is desirable to provide SVS systems and
methods that are able to validate topographical information
contained in a topographical database, in particular the
geographical location of runways and obstacles in the terminal area
of an airport. It is also desirable to provide such SVS systems and
methods that are capable of correcting any errors or biases in the
topographical database that may be determined by the validation.
Furthermore, other desirable features and characteristics of
exemplary embodiments will become apparent from the subsequent
detailed description and the appended claims, taken in conjunction
with the accompanying drawings and the foregoing technical field
and background.
BRIEF SUMMARY
[0006] Provided are aircraft synthetic vision systems that utilize
data from local area augmentation systems, and methods for
operating such aircraft synthetic vision systems. In one exemplary
embodiment, an aircraft synthetic vision display system (SVS)
includes a topographical database including topographical
information relating to an airport, a global positioning system
receiver that receives a satellite signal from a global positioning
satellite to determine a geographical position of the aircraft, and
a ground-based augmentation system receiver that receives a
ground-based signal from a ground-based transmitter associated with
the airport, wherein the ground-based signal includes geographical
information associated with the airport. The SVS further includes a
computer processor that retrieves the topographical information
from the topographical database based on the geographical position
of the aircraft, that retrieves the geographical information
associated with the airport, that validates the topographical
information using the geographical information associated with the
airport, and that corrects the topographical information using the
geographical information associated with the airport to generate
corrected topographical information. Still further, the SVS
includes a display device that renders three-dimensional synthetic
imagery of environs of the aircraft based on the corrected
topographical information.
[0007] In another exemplary embodiment, a method of operating a
synthetic vision system of an aircraft includes the steps of
receiving a satellite signal from a global positioning satellite to
determine a geographical position of the aircraft and receiving a
ground-based signal from a ground-based transmitter associated with
the airport, wherein the ground-based signal includes geographical
information associated with the airport. The method further
includes, using a computer processor, retrieving topographical
information based on the geographical position of the aircraft,
retrieving the geographical information associated with the
airport, validating the topographical information using the
geographical information associated with the airport, and
correcting the topographical information using the geographical
information associated with the airport to generate corrected
topographical information. The method further includes rendering
three-dimensional synthetic imagery of environs of the aircraft
based on the corrected topographical information.
[0008] This summary is provided to introduce a selection of
concepts in a simplified form that are further described below in
the detailed description. This summary is not intended to identify
key features or essential features of the claimed subject matter,
nor is it intended to be used as an aid in determining the scope of
the claimed subject matter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The present disclosure will hereinafter be described in
conjunction with the following drawing figures, wherein like
numerals denote like elements, and wherein:
[0010] FIG. 1 is a functional block diagram of a synthetic vision
system according to an exemplary embodiment of the present
disclosure;
[0011] FIG. 2 is an exemplary image that may be rendered on the
synthetic vision system of FIG. 1; and
[0012] FIG. 3 is a flow chart illustrating a method of operation
for the synthetic vision system of FIG. 1 in accordance with
exemplary embodiment of the present disclosure.
DETAILED DESCRIPTION
[0013] The following detailed description is merely exemplary in
nature and is not intended to limit the invention or the
application and uses of the invention. As used herein, the word
"exemplary" means "serving as an example, instance, or
illustration." Thus, any embodiment described herein as "exemplary"
is not necessarily to be construed as preferred or advantageous
over other embodiments. All of the embodiments described herein are
exemplary embodiments provided to enable persons skilled in the art
to make or use the invention and not to limit the scope of the
invention which is defined by the claims. Furthermore, there is no
intention to be bound by any expressed or implied theory presented
in the preceding technical field, background, brief summary, or the
following detailed description.
[0014] Embodiments of the present disclosure utilize ground-based
data sources located at an airport, such as a local area
augmentation system (LAAS), to validate the data from the
topographical databases (particularly navigational database 108,
runway database 110, and obstacle database 112). If the
topographical database information does not match the information
from the ground-based data source, then there is determined to be
an error or bias in the data from the topographical databases. The
error or bias is then corrected utilizing the information from the
ground-based data source. The corrected topographical information
is then utilized by the processor 104 to provide an accurate
display on the display device 116 of the SVS 100. The accurate
display includes an accurate runway position, accurate obstacle
positions, and accurate terrain renderings. With this verified and
corrected display, the SVS 100 can be used as a supplement to the
aircraft's instrument approach systems (e.g., ILS, VOR, GPS) until
about 150 feet height above threshold (HAT).
[0015] As used herein, the term "synthetic vision system" refers to
a system that provides computer-generated images of the external
scene topography from the perspective of the flight deck, derived
from aircraft attitude, high-precision navigation solution, and
database of terrain, obstacles, and relevant cultural features. A
synthetic vision system is an electronic means to display a
synthetic vision depiction of the external scene topography to the
flight crew. Synthetic vision creates an image relative to terrain
and airport within the limits of the navigation source capabilities
(position, altitude, heading, track, and the database limitations).
The application of synthetic vision systems is through a primary
flight display from the perspective of the flight deck or through a
secondary flight display.
[0016] Referring to FIG. 1, an exemplary synthetic vision system is
depicted and will be described in accordance with various
embodiments of the present disclosure. The system 100 includes a
user interface 102, a processor 104, one or more terrain databases
106, one or more navigation databases 108, one or more runway
databases 110, one or more obstacle databases 112, various sensors
113, a multi-mode receiver (MMR) 114, and a display device 116. The
user interface 102 is in operable communication with the processor
104 and is configured to receive input from a user 109 (e.g., a
pilot) and, in response to the user input, supply command signals
to the processor 104. The user interface 102 may be any one, or
combination, of various known user interface devices including, but
not limited to, a cursor control device (CCD) 107, such as a mouse,
a trackball, or joystick, and/or a keyboard, one or more buttons,
switches, or knobs. In the depicted embodiment, the user interface
102 includes a CCD 107 and a keyboard 111. The user 109 uses the
CCD 107 to, among other things, move a cursor symbol on the display
screen (see FIG. 2), and may use the keyboard 111 to, among other
things, input textual data.
[0017] The processor 104 may be any one of numerous known
general-purpose microprocessors or an application specific
processor that operates in response to program instructions. In the
depicted embodiment, the processor 104 includes on-board RAM
(random access memory) 103, and on-board ROM (read only memory)
105. The program instructions that control the processor 104 may be
stored in either or both of the RAM 103 and the ROM 105. For
example, the operating system software may be stored in the ROM
105, whereas various operating mode software routines and various
operational parameters may be stored in the RAM 103. It will be
appreciated that this is merely exemplary of one scheme for storing
operating system software and software routines, and that various
other storage schemes may be implemented. It will also be
appreciated that the processor 104 may be implemented using various
other circuits, not just a programmable processor. For example,
digital logic circuits and analog signal processing circuits could
also be used.
[0018] No matter how the processor 104 is specifically implemented,
it is in operable communication with the terrain databases 106, the
navigation databases 108, the runway databases 110, the obstacle
databases 112, and the display device 116, and is coupled to
receive various types of external data from the various sensors 113
(such as airspeed, altitude, air temperature, heading, etc.), and
various aircraft position-related data from the MMR 114, which
receives signals from various external position-related data
sources such as VOR, GPS, WAAS, LAAS, ILS, MLS, NDB, etc. The
processor 104 is configured, in response to the position-related
data, to selectively retrieve terrain data from one or more of the
terrain databases 106, navigation data from one or more of the
navigation databases 108, runway data from one or more of the
runway databases 110, and obstacle data from one or more of the
obstacle databases 112, and to supply appropriate display commands
to the display device 116. The display device 116, in response to
the display commands, selectively renders various types of textual,
graphic, and/or iconic information. A brief description of the
databases 106, 108, 110, and 112, the sensors 113, and the MMR 114,
at least in the depicted embodiment, will be provided.
[0019] The terrain databases 106 include various types of data
representative of the terrain over which the aircraft is flying,
and the navigation databases 108 include various types of
navigation-related data. These navigation-related data include
various flight plan related data such as, for example, waypoints,
distances between waypoints, headings between waypoints, data
related to different airports, navigational aids, obstructions,
special use airspace, political boundaries, communication
frequencies, and aircraft approach information. It will be
appreciated that, although the terrain databases 106, the
navigation databases 108, the runway databases 110, and the
obstacle databases 112 are, for clarity and convenience, shown as
being stored separate from the processor 104, all or portions of
either or both of these databases 106, 108, 110, 112 could be
loaded into the RAM 103, or integrally formed as part of the
processor 104, and/or RAM 103, and/or ROM 105. The databases 106,
108, 110, 112 could also be part of a device or system that is
physically separate from the system 100.
[0020] In one exemplary embodiment, the processor 104 is adapted to
receive terrain data from the terrain database 106 and navigation
data from the navigation database 108, operable, in response
thereto, to supply one or more image rendering display commands.
The display device 116 is coupled to receive the image rendering
display commands and is operable, in response thereto, to
simultaneously render (i) a perspective view image representative
of the terrain data and navigation data and (ii) one or more
terrain-tracing lines. The perspective view image includes terrain
having a profile determined by elevations of the terrain. Each
terrain-tracing line (i) extends at least partially across the
terrain, (ii) represents at least one of a ground-referenced range
to a fixed location on the terrain and a aircraft-referenced range
from the aircraft to a fixed range away from the aircraft, and
(iii) conforms to the terrain profile.
[0021] Notably, the visibility of the terrain information displayed
on the screen of visual display 116 may be enhanced responsive to
one or more suitable algorithms (e.g., implemented in software)
executed by the processor 104, which functions to determine an
aircraft's current position, heading and speed, and initially loads
a patch of terrain data for a region that is suitably sized to
provide a rapid initialization of the data. The processor 104
monitors the aircraft's position, heading, and speed (also attitude
when pertinent) from sensors 113 and MMR 114, and continuously
predicts the potential boundaries of a three-dimensional region
(volume) of terrain in the flight path based on the aircraft's
then-current position, heading and speed (and attitude when
pertinent). The processor 104 compares the predicted boundaries
with the boundaries of the initially loaded terrain data, and if
the distance from the aircraft to a predicted boundary is
determined to be less than a predetermined value (e.g., distance
value associated with the boundaries of the initially loaded data),
then the processor 104 initiates an operation to load a new patch
of terrain data that is optimally sized given the aircraft's
current position, heading and speed (and attitude when pertinent).
Notably, for this example embodiment, the processor 104 can execute
the data loading operations separately from the operations that
determine the aircraft's current position, heading and speed, in
order to maintain a constant refresh rate and not interfere with
the continuity of the current display of terrain.
[0022] One important aspect of situational awareness is to be aware
of obstacles which pose a threat to the craft. This is particularly
true for aircraft during take-off and landing or other low altitude
operations and even more so in low visibility conditions. Some
displays depict information on obstacles in or near the aircraft's
travel path. Obstacle data should be presented in such a way that
it will provide timely awareness of the height, location, and
distance of possible threats without distracting from the other
primary information on the display. The processor 104 generates
data for display on the display 116 based on the position of the
aircraft and obstacle data. Obstacles can be sought and displayed
for different locations along one or more flight paths, thereby
assisting an operator choose the safest path to follow. The
obstacle database 112 may contain data regarding obstacles, wherein
the processor 104 sends a signal to the display 116 to render a
simulated graphical representation of the obstacle based on that
data, or the obstacle database may contain actual images of the
obstacles, wherein the processor 104 sends a signal to display the
actual image based on the positional data.
[0023] The processor 104 analyzes the data received from the
obstacle database 112 and determines if the obstacles are within a
selected distance from the aircraft. Obstacles that are not within
a selected distance are not displayed. This procedure saves
processor load and reduces display clutter by only displaying
obstacles that are of interest to the aircraft. Size, speed, and
altitude of the aircraft and size of the obstacle may be considered
along with distance in determining whether to display the
obstacle.
[0024] The runway database 110 may store data related to, for
example, runway lighting, identification numbers, position, and
length, width, and hardness. As an aircraft approaches an airport,
the processor 104 receives the aircraft's current position from,
for example, the MMR 114 and compares the current position data
with the distance and/or usage limitation data stored in the
database for the landing system being used by that airport.
[0025] The sensors 113 may be implemented using various types of
sensors, systems, and or subsystems, now known or developed in the
future, for supplying various types of aircraft data. The aircraft
data may also vary, but preferably include data representative of
the state of the aircraft such as, for example, aircraft speed,
heading, altitude, and attitude. The number and type of data
sources received into MMR 114 may also vary. However, for ease of
description and illustration, only a VHF data broadcast (VDB)
receiver 118 functionality and a global position system (GPS)
receiver 122 functionality are depicted in FIG. 1, as these
receivers are particularly relevant to the discussion of the
present disclosure. As noted above, though, modern MMRs include the
ability to receive many more signals beyond the illustrated GPS and
VDB receiver functionalities.
[0026] The GPS receiver 122 functionality is a multi-channel
receiver, with each channel tuned to receive one or more of the GPS
broadcast signals transmitted by the constellation of GPS
satellites (not illustrated) orbiting the earth. Each GPS satellite
encircles the earth two times each day, and the orbits are arranged
so that at least four satellites are always within line of sight
from almost anywhere on the earth. The GPS receiver 122, upon
receipt of the GPS broadcast signals from at least three, and
preferably four, or more of the GPS satellites, determines the
distance between the GPS receiver 122 and the GPS satellites and
the position of the GPS satellites. Based on these determinations,
the GPS receiver 122, using a technique known as trilateration,
determines, for example, aircraft position, groundspeed, and ground
track angle. These data may be supplied to the processor 104, which
may determine aircraft glide slope deviation therefrom. Preferably,
however, the GPS receiver 122 is configured to determine, and
supply data representative of, aircraft glide slope deviation to
the processor 104.
[0027] The VDB receiver 118 functionality is a multi-channel
receiver configured to received VHF signals in the 108.0 to 117.975
MHz band from a ground station that is associated with a particular
airport. The VHF data signals include corrections for GPS satellite
signals. The VHF data signals also include broadcast information
that is used to define a reference path typically leading to the
runway intercept point. This data can include information for as
many as 49 different reference paths using a single radio
frequency. (Even more reference paths could be supported by using
additional radio frequencies.) The VDB signal employs a
differential 8-phase shift key (D8PSK) waveform. This waveform was
chosen because of the relatively good spectral efficiency in terms
of the number of bits per second that can be supported within a 25
kHz frequency assignment. Four message types are currently defined
for VDB signals. Message Type 1 includes differential correction
and integrity related data for the GPS satellites. Message Type 4
includes final approach segment definitions for each runway end or
approach at the airport.
[0028] The display device 116, as noted above, in response to
display commands supplied from the processor 104, selectively
renders various textual, graphic, and/or iconic information, and
thereby supply visual feedback to the user 109. It will be
appreciated that the display device 116 may be implemented using
any one of numerous known display devices suitable for rendering
textual, graphic, and/or iconic information in a format viewable by
the user 109. Non-limiting examples of such display devices include
various cathode ray tube (CRT) displays, and various flat panel
displays such as various types of LCD (liquid crystal display) and
TFT (thin film transistor) displays. The display device 116 may
additionally be implemented as a panel mounted display, a HUD
(head-up display) projection, or any one of numerous known
technologies. It is additionally noted that the display device 116
may be configured as any one of numerous types of aircraft flight
deck displays. For example, it may be configured as a
multi-function display, a horizontal situation indicator, or a
vertical situation indicator, just to name a few. In the depicted
embodiment, however, the display device 116 is configured as a
primary flight display (PFD).
[0029] Referring to FIG. 2, exemplary textual, graphical, and/or
iconic information rendered by the display device 116, in response
to appropriate display commands from the processor 104 is depicted.
It is seen that the display device 116 renders a view of the
terrain 202 ahead of the aircraft, preferably as a
three-dimensional perspective view, an altitude indicator 204, an
airspeed indicator 206, an attitude indicator 208, a compass 212,
an extended runway centerline 214, a flight path vector indicator
216, and an acceleration cue 217. The heading indicator 212
includes an aircraft icon 218, and a heading marker 220 identifying
the current heading (a heading of 174 degrees as shown). An
additional current heading symbol 228 is disposed on the zero pitch
reference line 230 to represent the current aircraft heading when
the center of the forward looking display 116 is operating in a
current track centered mode. The center of the forward looking
display 116 represents where the aircraft is moving and the heading
symbol 228 on the zero-pitch reference line 230 represent the
current heading direction. The compass 212 can be shown either in
heading up, or track up mode with airplane symbol 218 representing
the present lateral position. Additional information (not shown) is
typically provided in either graphic or numerical format
representative, for example, of glide slope, altimeter setting, and
navigation receiver frequencies.
[0030] An aircraft icon 222 is representative of the current
heading direction, referenced to the current ground track 224, with
the desired track as 214 for the specific runway 226 on which the
aircraft is to land. A distance remaining marker 227 may be shown
on the display 116, in a position ahead of the aircraft, to
indicate the available runway length ahead, and the distance
remaining marker 227 may change color if the distance remaining
becomes critical. Lateral deviation marks 223 and vertical
deviation marks 225 on perspective conformal deviation symbology
represent a fixed ground distance from the intended flight path.
The desired aircraft direction is determined, for example, by the
processor 104 using data from the navigation database 108, the
sensors 113, and the external data sources 114. It will be
appreciated, however, that the desired aircraft direction may be
determined by one or more other systems or subsystems, and from
data or signals supplied from any one of numerous other systems or
subsystems within, or external to, the aircraft. Regardless of the
particular manner in which the desired aircraft direction is
determined, the processor 104 supplies appropriate display commands
to cause the display device 116 to render the aircraft icon 222 and
ground track icon 224.
[0031] As noted previously, the usefulness of the SVS system 100
for approach and landing is limited by the accuracy of the
topographical databases 106, 108, 110, and 112, particularly in the
terminal area of the airport. It has been discovered, for example,
that in some instances, published terminal area topographical data
may include unintended errors or biases in relation to the
geographic position of certain features, such as runways (database
110), obstacles (database 112), etc. If these errors or biases are
then introduced into the SVS topographical databases, then the 3-D
rendered images presented to the pilot on the SVS may not match the
aircraft's actual environment, which is problematic in the context
of flying a precision approach to the airport supplemented by the
SVS.
[0032] Embodiments of the present disclosure utilize ground-based
data sources located at an airport, such as a local area
augmentation system, to validate the data from the topographical
databases (particularly runway database 110). If the topographical
database information does not match the information from the
ground-based data source, then there is determined to be an error
or bias in the data from the topographical databases. The error or
bias is then corrected utilizing the information from the
ground-based data source. The corrected topographical information
is then utilized by the processor 104 to provide an accurate
display on the display device 116 of the SVS 100. The accurate
display includes an accurate runway position, accurate obstacle
positions, and accurate terrain renderings. With this verified and
corrected display, the SVS 100 can be used as a supplement to the
aircraft's instrument approach systems (e.g., ILS, VOR, GPS) until
about 150 feet height above threshold.
[0033] A LAAS at an airport generally includes local reference
receivers located around the airport that send data to a central
location at the airport. This data is used to formulate a
correction message (Type 1), which is then transmitted to users via
VDB. The VDB receiver 118 functionality on the aircraft uses this
information to correct GPS signals, which then provides a standard
ILS-style display to use while flying a precision approach. The
LAAS VDB transmitters also transmit broadcast information that is
used to define a reference path typically leading to the runway
intercept point (message Type 4), which includes final approach
segment definitions for each runway end or approach at the
airport.
[0034] An aircraft on approach to the airport will begin receiving
LAAS VDB signals once the aircraft enters within the usable range
of the LAAS system, which is usually about a 25 nm radius from the
airport. Prior to entering the usable range, the SVS 100 is
receiving GPS data (receiver functionality 122 of the MMR 114). SVS
100 relies on the GPS data, and the topographical databases 106,
108, 110, and 112 to display the image on display 116. Upon
entering the LAAS usable range, the aircraft begins to receive the
VDB signal from the LAAS via the VDB receiver 118 functionality of
the MMR 114. Message Type 4 of the VDB signal includes final
approach segment definitions, for example in terms of geographic
reference coordinates. The topographical database information,
particularly that of databases 108, 110 and 112, may then be
validated using the message Type 4 information from the VDB signal.
If the topographical database information does not match the
message Type 4 information, then there may be determined to be an
error or bias in the topographical database information. The
message Type 4 information from the VDB signal is then used to
correct the topographical information. The corrected topographical
information is then used to render the SVS display on display
device 116, providing the flight crew with a high-fidelity SVS
display that may be used as a supplement for use during an
instrument approach, down to a HAT of about 150 feet.
[0035] The use of LAAS message Type 4 information as validation
should not be understood to exclude the use of other validation
data source. For example, in addition to the foregoing described
validation, message Type 1 information may be used to validate and
correct the GPS signal, which may then be used by the SVS 100 as
part of its display/validation scheme. Moreover, satellite-based
correction signals from a wide area augmentation system (WAAS) may
be used for the same purpose. Still further, onboard validation
means, such as inertial navigation systems (INS), may be used to
validate and cross-check the received GPS signal for purposes of
providing an accurate SVS display that is usable as a supplement
with instrument approaches.
[0036] In some embodiments, it is proposed that that the VDB is
modified to carry more information, e. g., runway closure NOTAM,
runway occupancy status, hold short traffic information, etc., to
facilitate a timely and improved visual situational awareness. This
runway closure NOTAM, runway occupancy status, or hold short
traffic information may be displayed to the flight crew as an
appropriate graphical or textual indication on the display 116 of
SVS 100. For example, runway closure NOTAMs may be provided in
text, runway occupancy status may be indicated by an aircraft
symbol on the runway, and hold short traffic information may be
indicated as an appropriate line or bar at the hold short point of
the runway.
[0037] In further embodiments, the SVS 100 may include a "level of
service" monitor to indicate the health of the SVS 100. Various
monitors may validate the information and allow the synthetic scene
to be used for navigation and lower minimums. The level of service
monitor may be provided on display device 116, and may include
green text that lists the type of approach, the unique identifier
for the approach, and a label that indicates the health of the SVS
100. When the label is written in green text, it means that the
approach is usable, and that all of the validation scheme are
operating properly (and that if any error or bias has been
detected, it has been appropriately corrected using the VDB
information). An audible signal or its accompanying text in an
amber box in the level of service monitor means the approach must
either be abandoned or flown as a normal ILS or other instrument
approach. Below the normal ILS or other approach minimums, the box
turns red and pilots must fly the missed-approach procedure.
[0038] FIG. 3 provides an exemplary flowchart of a method of
operation 300 of the SVS 100 in accordance with an exemplary
embodiment of the present disclosure. At step 301, the SVS receives
a GPS signal indicating a position of the aircraft. At step 303,
the SVS receives a VDB signal including final approach segment
information from a ground-based augmentation system (i.e., a LAAS)
at an airport. At step 305, the SVS accesses one or more
topographical databases (i.e., terrain, navigation, runway, and/or
obstacle) and retrieved topographical information pertaining to the
position of the aircraft. At step 307, the SVS uses the VDB signal
to validate the topographical information. Step 309 is a
determining step wherein the SVS determines whether the
topographical information has been validated, i.e., whether the
topographical information matches the VDB signal information. At
step 311, if the topographical information has been validated, the
SVS displays a synthetic vision image to the flight crew of the
aircraft on a flight display based on the topographical
information. At step 313, if the information does not match, then
the topographical information is corrected using the VDB
information, namely the final approach segment information. Then,
at step 315, the SVS displays a synthetic image to the flight crew
of the aircraft on the flight display based on the correct
topographical information.
[0039] In this document, relational terms such as first and second,
and the like may be used solely to distinguish one entity or action
from another entity or action without necessarily requiring or
implying any actual such relationship or order between such
entities or actions. Numerical ordinals such as "first," "second,"
"third," etc. simply denote different singles of a plurality and do
not imply any order or sequence unless specifically defined by the
claim language. The sequence of the text in any of the claims does
not imply that process steps must be performed in a temporal or
logical order according to such sequence unless it is specifically
defined by the language of the claim. The process steps may be
interchanged in any order without departing from the scope of the
invention as long as such an interchange does not contradict the
claim language and is not logically nonsensical.
[0040] Furthermore, depending on the context, words such as
"connect" or "coupled to" used in describing a relationship between
different elements do not imply that a direct physical connection
must be made between these elements. For example, two elements may
be connected to each other physically, electronically, logically,
or in any other manner, through one or more additional
elements.
[0041] While at least one exemplary embodiment has been presented
in the foregoing detailed description of the invention, it should
be appreciated that a vast number of variations exist. It should
also be appreciated that the exemplary embodiment or exemplary
embodiments are only examples, and are not intended to limit the
scope, applicability, or configuration of the invention in any way.
Rather, the foregoing detailed description will provide those
skilled in the art with a convenient road map for implementing an
exemplary embodiment of the invention. It being understood that
various changes may be made in the function and arrangement of
elements described in an exemplary embodiment without departing
from the scope of the invention as set forth in the appended
claims.
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