Note: Descriptions are shown in the official language in which they were submitted.
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TITLE OF THE INVENTION
METHOD AND APPARATUS FOR
PREDICTIVE ALTITUDE DISPLAY
FIELD OF THE INVENTION
The present invention relates to avionics, and more
particularly to altitude displays and terrain awareness
warning systems.
BACKGROUND OF THE INVENTION
A conventional altitude display for a terrain
awareness warning system (TAWS) for a given aircraft
provides a pilot with a visual display of the terrain
having an altitude higher than the aircraft, as well as the
terrain within some distance, usually 2000', below an
aircraft.
Referring to prior art FIG. 1, an environment is shown
in which a conventional altitude display could be
important. In situation I, an aircraft 12 is flying at an
altitude X along a direction vector 16. In situation II,
an aircraft 12' is flying at an altitude X' along a
direction vector 16'. In situation III, an aircraft 12"
is flying at an altitude X" along a direction vector 16".
Finally, in situation IV, an aircraft 12111 is flying at an
altitude X111 along a direction vector 161". The
aircrafts 12, 12', 1211, and 12111 are flying with
direction vectors 16, 16', 16", 16111, respectively, such
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that an obstruction 14 having height Y is within a forward
arc, centered on the respective direction vector, as
monitored by the conventional altitude display aboard each
respective aircraft.
Starting by considering situation IV, a conventional
altitude display would typically give a visual signal as
the height Y of the obstruction 14 is greater than the
altitude X"' of the aircraft 12"'. In other words, X"'
< Y. An audible alert may be given as well if suitable
criteria regarding time-to-impact of the terrain feature
are also met. In all cases, the height Y and altitude X`
may be measured by radio height, altitude above sea level,
or other means, and preferably the same type of
measurement, is employed for both distances. The visual
signal in this situation would typically be a red area,
such as a spot or square, on a cockpit display. The term
`RED' is shown in the figure to denote the range of
operation which would result in a red area being displayed.
The red area would be indicated to be at a range Z and at a
bearing corresponding to the direction of the obstruction
14 relative to the centerline of the aircraft 121".
In situation III, a conventional altitude display
would also typically give a red visual signal as the height
Y of the obstruction 14 is within a predetermined elevation
buffer "D" and a predetermined time-to-impact from the
altitude X11 of the aircraft 12". This elevation buffer D
is typically 700' or 1000' during enroute navigation, and
the alert would be given if X " -Y < D. As before, the red
area would be indicated to be at a range Z and at a bearing
corresponding to the direction of the obstruction 14
relative to the centerline of the aircraft 12". Also as
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before, an audible signal may also be given if certain
criteria are met.
In situation II, a conventional altitude display would
typically just display a visual signal as the altitude X'
of the aircraft 12' is greater, than the predetermined
elevation buffer D from the height Y of the obstruction 14,
by a first distance dl . In other words, X' - Y > D + dl, d1
is also typically 1000'. The aircraft 12' would not be
considered to be completely free of the obstruction 14,
however, and for this reason the visual signal would be of
a cautionary nature. The visual signal would typically be
a yellow area, such as a spot or square, on the cockpit
display. As such, `YELLOW' indicates this range. As with
the red areas, the yellow area would be indicated to be at
a range Z and at a bearing corresponding to the direction
of the obstruction 14 relative to the centerline of the
aircraft 12'.
Finally, in situation I, a conventional altitude
display would typically just display a visual signal as the
altitude X' of the aircraft 12' is greater than the height
Y of the obstruction 14 by not only the elevation buffer D
and the first distance dl, but also by a second distance d2.
In other words, X' - Y > D + dl + d2. d2 is again typically
1000'. The aircraft 12 would be considered to be mostly
free of the obstruction 14, however, and for this reason
the visual signal would typically be a green area, such as
a spot or square, on the cockpit display. Again, `GREEN'
indicates this range. As with the red and yellow areas,
the green area would be indicated to be at a range Z and at
a bearing corresponding to the direction of the obstruction
14 relative to the centerline of the aircraft 12.
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At higher aircraft altitudes, no colored area, or a
black area, would be indicated. Here, `NONE' is shown in
the figure to denote this range.
Such altitude displays are clearly useful for warning
pilots of impending dangerous terrain. However, such
systems fail to account for important factors such as the
actual flight path of the aircraft. As a result, their
accuracy may be less than desired. For example, if an
aircraft is climbing, the above described prior art
altitude display may report a red area where one is not
warranted. In the same way, if an aircraft is high but
descending, the above-described prior art altitude display
may display a green area where a red area is warranted.
SUMMARY OF THE INVENTION
The present invention overcomes the disadvantages of
the prior art noted above.
In one aspect, the invention is directed towards a
method for providing an indication of aircraft height
relative to an obstruction in a terrain awareness warning
system. The method includes steps of receiving a first
datum indicative of a geographic feature of an obstruction,
receiving a second datum indicative of a lateral distance
of the geographic feature from an aircraft, receiving a
third datum indicative of a height of the aircraft,
receiving a fourth datum indicative of a flight path of the
aircraft, calculating a projected height of the aircraft at
the location of the obstruction using the first through
fourth data, generating a result signal based on the
projected height and the first datum, and displaying a
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colored indication on a display screen based on the
generated result signal.
Implementations of the method may include one or more
of the following. The first datum may be a height of the
obstruction. The colored indication may be a colored area
on a display screen having a color such as red, yellow,
green, or black. The elevation buffer may be zero. The
receiving a fourth datum may further include resolving the
flight path of the aircraft into components including a
lateral flight path and a vertical flight path. The method
may further include: calculating a flight path angle of the
aircraft from the received fourth datum, calculating an
effective altitude of the aircraft by adding to the third
datum a value equal to the second datum multiplied by the
tangent of the flight path angle, generating a first alert
signal if the effective altitude is less than the sum of
the first datum and a elevation buffer, sounding an audible
alarm with the first alert signal, displaying a first
colored indication at a display location corresponding to
the second datum as the first alert signal, generating a
second alert signal if the effective altitude is greater
than the sum of the first datum and a elevation buffer but
less than a sum of the first datum, the elevation buffer,
and a first distance, or displaying a second colored
indication at a display location corresponding to the
second datum as the second alert signal.
In another aspect, the invention is directed towards a
computer program, stored in a machine-readable format, for
a terrain awareness warning system. The program causes a
computer to: receive a first datum indicative of a
geographic feature of an obstruction; receive a second
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datum indicative of a lateral distance of the geographic
feature from an aircraft; receive a third datum indicative
of a height of the aircraft; receive a fourth datum
indicative of a flight path of the aircraft; calculate a
projected height of the aircraft at the location of the
obstruction using the first through fourth data; and
generate a result signal based on the projected height and
the first datum.
In yet another aspect, the invention is directed
towards an apparatus for providing an indication of
aircraft height relative to an obstruction in a terrain
awareness warning system. The apparatus includes a first
input for a first signal from an instrument measuring a
height of an aircraft, a second input for a second signal
from an instrument measuring a location of the aircraft, a
third input for a third signal from an instrument providing
information about geographic features of terrain
surrounding the aircraft, and a fourth input for a fourth
signal from an instrument measuring a flight path of the
aircraft. The apparatus includes means for employing the
signals from the first through fourth inputs to calculate
an effective height of the aircraft relative to at least
the third input, and a screen display for graphically
displaying the results of the calculation.
Implementations of the apparatus may include one or
more of the following. The instrument measuring height and
location of the aircraft may include an altimeter. The
instrument providing information about geographic features
of terrain surrounding the aircraft, as well as the
instrument measuring a flight path of the aircraft, may be
aids to navigation, such as a global positioning system
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unit. The apparatus may further include a conventional
TAWS altitude display and means to toggle the screen
display between the conventional TAWS altitude display and
the screen display for graphically displaying the results
of the calculation. The first through fourth inputs may
form at least a portion of a parallel data bus or a serial
data stream.
In a further aspect, the invention is directed towards
a method of performing terrain awareness warning for an
aircraft. The method includes steps of collecting data
about terrain features in the vicinity of an aircraft,
collecting data of the lateral distance and bearing of the
terrain features from the aircraft, collecting data of the
height and flight path of the aircraft, calculating a
projected height of the aircraft at the location of each of
the terrain features based on the collected data of the
height and flight path of the aircraft, and generating
result signals based on the projected height, the collected
data of terrain features, and the bearing of the terrain
features. The method further includes displaying colored
indications on a display screen, with respect to bearing,
based on the generated result signals.
In still a further aspect, the invention is directed
towards a method for providing an indication of lateral
aircraft position relative to an obstruction in a terrain
awareness warning system. The method includes steps of
receiving a first datum indicative of the bearing of an
obstruction relative to an aircraft, receiving a second
datum indicative of a lateral distance of the obstruction
from the aircraft, and receiving third data indicative of a
flight path of the aircraft. The method further includes
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steps of calculating a projected flight path of the
aircraft relative to the obstruction using the first
through third data and determining a distance between the
projected flight path and the obstruction at a series of
points along the projected flight path. The method
includes steps of generating a result signal based on the
determined distance, and displaying a colored indication on
a display screen based on the generated result signal with
respect to the bearing.
Advantages of the invention may include one or more of
the following. The invention allows for more accurate
terrain displays, giving the pilot a more reliable
indicator of the relative danger of forward terrain. The
invention provides this increased accuracy in part by
taking into account factors, such as the flight path angle
of the aircraft, when calculating and displaying alerts.
As a result, false warnings are eliminated and dangerous
situations that would not have been noticed by prior
systems are avoided.
Other advantages will be apparent from the description
that follows, including the figures and the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic depiction of various scenarios
of aircraft flight with respect to an obstruction;
FIG. 2 is a schematic drawing of an apparatus
according to an embodiment of the present invention,
showing in particular the display and button layout;
FIG. 3A is a schematic depiction of various scenarios
of aircraft flight with respect to an obstruction, showing
in particular the flight paths and accompanying alert
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situations according to an embodiment of the invention in
which an aircraft has a positive flight path angle;
FIG. 3B is a schematic of a notation scheme, with
accompanying axes, used to describe features of embodiments
of the invention;
FIG. 4 is a schematic depiction of various scenarios of
aircraft flight with respect to an obstruction, showing in
particular the flight paths and accompanying alert
situations according to an embodiment of the invention in
which an aircraft has a negative flight path angle;
FIG. 5 is a schematic depiction of various scenarios of
aircraft flight with respect to an obstruction, showing in
particular the flight paths and accompanying alert
situations according to an embodiment of the invention in
which an aircraft has a positive yaw angle;
FIG. 6 is a flowchart of a method according to an
embodiment of the present invention; and
FIG. 7 is a block diagram of an apparatus according to
an embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to FIG. 2, a display apparatus 100 for a
terrain awareness (TAWS) system is shown that may
incorporate the present invention. The display apparatus 100
employs a screen display 102, which may be an LCD rear
projection screen such as that disclosed in U.S. Pat. No.
6,259,378, owned by the assignee of the present invention.
The display apparatus 100 further includes various
surrounding buttons and interfaces.
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An exemplary layout for the display apparatus 100 will
now be described. However, it should be appreciated that
the particular button and function layout described below
is merely an example and the invention is not limited
thereto.
Upon depression of the toggle button 104, the screen
display may toggle between a topographic display and a
relative altitude display. Upon depression of the
predictive altitude display ("PRED") button 106, the screen
display 102 changes to the PRED display, which is described
in greater detail below.
A traffic display button 108 may cause a display of
local air traffic in the vicinity of the aircraft. This
function may employ as inputs the sensor readings from
transponders on aircraft operating within radio range of
the subject aircraft. An auxiliary button 110 may display
a variety of information, such as weather, ancillary
navigational aids, and so on.
A function button 126 may be provided to allow the
user to select more than the usual input or inputs from the
various other buttons. For example, the function button
126 may be used to enhance the ability of the user to
perform a setup of the apparatus. As another example,
during an alert or warning, pressing the function button
126 may result in a muting of the alert or warning.
Preferably, if an alert status were indicated, the display
screen 102 would switch to a display of that function which
would allow the pilot to most effectively find a solution
to the situation. In many cases, the PRED function would
be the most pertinent such display.
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A light sensor 120 may be employed to automatically
control the brightness and contrast of the screen display
102 for improved visibility. A micro-USB port 118 may be
employed to allow an external input/output of data from the
display apparatus 100. As explained in more detail below,
various data, such as airport runway information,
topographical data and runway approach data may be up-
loaded to the display apparatus 100 prior to use. It may
be necessary to periodically update this information and
use of the micro-USB port 118 may be used for this purpose,
although other methods and apparatus are within the scope
of the invention. For example, the data may be updated by
wireless link.
Finally, a ranging button 122 may allow a zoom in or
out of the display, and a VUE button 124 may toggle the
display between a 360 display and a forward arc display of,
e.g., 70 . Such choices may especially be useful for the
functions invoked by buttons 104, 106, and 108.
Generally, in use, the display apparatus 100 receives
data concerning the position of the aircraft, its ground
track, lateral track, flight path, altitude, height off
ground and other data. This data is compared with pre-
stored data concerning terrain in the proximity of the
aircraft as well as terrain that will be within proximity
of the aircraft within a selected look ahead distance or
time based on the projected flight path. The desired look
ahead distance or time may be dynamically adjusted by the
user or system. For example, the system may be set to a 10
second look-head, which would provide a display of terrain
that the aircraft will come in proximity with in the next
10 seconds, based on the projected flight path, which may
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be calculated based on data including the current heading,
air speed, ground track, etc. The system may adjust the
look ahead distance/time based on phase of flight.
Terrain as used herein includes natural as well as
man-made obstacles and topographical features. For
example, tall buildings, tall wire towers and mountain
ranges are all terrain as used herein.
Depending on the relationship (or projected
relationship) of the aircraft to the terrain, the terrain
may or may not be displayed on the display device 100. For
example, if it appears that the aircraft will fly into or
very close to the terrain, the terrain may be displayed in
red on the display device 100 and/or an audible warning may
be generated to alert the user of the danger if other
appropriate criteria are met. For somewhat less
threatening situations, the terrain may be displayed in
yellow and/or an audible alert may be generated as above.
For situations in which the aircraft is not in a
threatening relationship to the terrain, the terrain may be
displayed in green, and for terrain that is sufficiently
distanced from the aircraft (either far below the aircraft
flight path or far afield from it), the terrain may not be
displayed.
Referring now to FIG. 3A, a schematic depiction of a
situation is given which may employ an embodiment of the
present invention. In particular, an aircraft 122 having
an altitude X has a flight path 126 which will take the
aircraft 122 in the proximity of an obstruction 124. The
obstruction 124 is of course schematic in nature and should
be understood to encompass any terrain feature.
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The aircraft 122 is shown with three different flight
paths: a level flight path 126, an ascending flight path
126', and a descending flight path 126". The amount of
ascent or descent is given by flight path angle a. It will
be clear that flight path angle a may be either positive
(ascending, flight path 126') or negative (descending,
flight path 126"). FIG. 3A primarily shows the effects of
a positive flight path angle. The effects of a negative
flight path angle are shown in FIG. 4.
In a conventional altitude display, each flight path
126, 126', and 126" would result in the same display,
depending only on the values of X, Y, dl, d2, Z, and D as
described above. In the present invention, amongst other
features, however, flight path angle a is taken into
account in order to provide a more accurate display of the
terrain in the vicinity of the aircraft.
The following ranges of operation are now defined
according to an embodiment of the invention, although one
of ordinary skill in the art will understand how the
methodology may be extended to cover situations involving a
greater or lesser number of ranges of operation (the
following example shows four ranges of operation):
(I) `Red' Situation
In this situation, the aircraft 122 is flying with an
altitude termed here an "effective altitude"
Xeff = X+( which leads to:
Xeff Y + D
X + 5 < Y + D , where S = Z tan a, and finally
X < Y + D - b
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and where a is measured from the horizon and is
positive for an ascent. This range of operation is termed
the `PREDICTIVE RED', and the same is indicated in FIG. 3A.
As the above equation shows, a positive value of 5 serves
to decrease the sum Y+D-5, this leading to an overall
lessening of the altitude at which the red alert would be
caused. In other words, a positive a, i.e. a positive
flight path angle or ascent, leads to the red range of an
aircraft encompassing a lesser number-of features than
before, as the "less high" features may no longer be
displayed as a red area. Equivalently, it is less likely a
given terrain feature will be displayed as being in the red
range of an aircraft if the aircraft has a positive a. The
overall effect is to shift the red range to higher
altitudes by an amount 5, as shown in the figure.
In any case, at the bearing of the obstruction 124,
the display screen 102 would display a first alert signal,
such as a colored indication, e.g., a red area or set of
pixels, at range Z. For this type of alert, an audible
alert or alarm to be sounded to the pilot to accompany the
visual alert if other criteria of the audible alert are
satisfied, such as a calculated time-to-impact with a
terrain feature being less than a predetermined threshold.
5, or equivalently a, provides a more reliable
indicator of the threat posed by the obstruction 124 as the
calculation using b or a predicts the altitude the aircraft
122 will have achieved when the aircraft is incident upon
the obstruction, rather than always assuming level flight.
An example is now given as to how the above
calculation may be applied. It will be clear to one of
skill in the art, given the teaching of the above and
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below, how to apply the calculation to other scenarios, and
in particular the scenarios below for the other ranges in
this series. An aircraft is flying in level flight at
1,500' towards an obstruction 3 miles away having a height
of 1000'. The elevation buffer is 1000', so a red area of
warning is displayed as the appropriate condition is met,
i.e., as X (1500') <_ Y (1,000') + D (1,000') - S (Z tan a,
which is zero for level flight (flight path angle a = 0)).
If, however, the aircraft is climbing at flight path angle
5 , then the calculation is now:
X <- Y + D - 5
<- 1,0001 + 1,0001 3 miles (5,2801/1 mile) tan 5
-< 2,000' - 3 miles (5,280'/1 mile) tan 5
<- 2,0001 - 1,3861 <- 614'
Here the condition is not met as X (1,500') is not
less than or equal to 614'. Thus, the ascent at angle a
has removed the red situation condition from the display
screen 102 and the red area is no longer displayed.
(II) `Yellow' Situation
In this situation, the aircraft 122 is flying with:
Y + D - S <- X <- Y + D + di- 5, where S is defined as
.
above for M.
For X meeting the above condition, the display screen
102 would display a second alert signal, such as a colored
indication of a yellow area or set of pixels, at range Z at
the bearing of the obstruction 124. Again, the yellow
range only encompasses higher terrain features than before,
as some will have shifted to the green or black ranges as
shown in the figure. In particular, and as above, the
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overall effect is to shift the yellow range to higher
altitudes.
(III) `Green' Situation
In this situation, the aircraft 122 is flying with:
Y + D + d1 - 5 < Xeff <_ Y + D + d1 + d2 - b
For Xeff meeting the above condition, the display
screen 102 would display a third alert signal, such as a
colored indication of a green area, at range Z at the
bearing of the obstruction 124. Analogously with the
above, the green range only encompasses higher terrain
features than before, as some will have shifted to the
black range as shown in the figure.
(IV) `Black' or `No Colored Area' Situation
In this situation, the aircraft 122 is flying with:
Y + D + d1 + d2 - 5 < Xeff
For Xeff meeting the above condition, the display
screen 102 would display a black area at range Z at the
bearing of the obstruction 124, or may alternatively
display no color. In either case, the pilot would be
undistracted by the display. That is, for such a terrain
feature as the obstruction 124, the aircraft would be in no
danger of collision.
FIG. 4 shows the above description and range
definitions in the case where a, and thus S (=Z tan a), are
negative. The negative a thus shifts the red, yellow, and
green terrain boundaries to lower altitudes, thus making it
more likely a given terrain feature will cause an alert.
In the extreme case shown in FIG. 4, the angle a is such
that almost any terrain would fall within the red range.
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Other refinements of this technique may be similarly
applied. For example, at another level of sophistication,
a second derivative may be applied to the calculation of b.
In particular, it is clear from the above that the
calculation of b assumed a constant vertical flight path
velocity, i.e., a constant first derivative of vertical
flight path. This type of calculation may well suit most
flight paths; generally, for relatively small a, the
vertical flight path velocity may be assumed constant, at
least over the short sampling time constant of the control
electronics driving and monitoring this type of system.
However, where this is not the case, consideration of the
2d derivative of flight path, or even higher order
derivatives of flight path, may be added to the calculation
to even further refine the estimate of Xeff relative to the
surrounding terrain.
At another level of sophistication, many types of
altitude displays may more preferably display range as a
function of time, rather than of distance. In other words,
rather than having the range of the display be, e.g., 10
miles, the range is displayed as, e.g., three minutes, or
whatever time period would be required for the aircraft to
traverse the 10 miles (in this example).
In this type of situation, the above calculations
would be performed, but with the appropriate distances
divided by the velocity or velocity component. For
example, TZ, a time period associated with the range Z,
would become the previous range, Z, divided by the lateral,
i.e., non-vertical, component of velocity in the direction
towards the particular obstruction. Similarly, To, the time
period associated with the amount of ascent or descent b,
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would become the previous 5 divided by the vertical
component of velocity v-1-.
In this scheme, the following definitions would apply
(Taircraft being the time available to the aircraft and pilot
prior to incidence upon the obstruction):
(I) Red Situation
Taircraft <_ (Y + D V1
(II) Yellow Situation
(Y + D - 6) / v1 <_ Taircraft <_ (Y + D + di - 6) / v1
(III) Green Situation
In this situation, the aircraft 122 is flying with:
(Y + D + dl - 5) / v1 < Taircraft <_ (Y + D + dl + d2 - (5) / v1
(IV) Black or No Colored Area Situation
(Y + D + dl + d2 - 5) / v1 < Taircraft
At another level of sophistication, and referring to
FIG. 5, an azimuthal or yaw angle cp may also enter the
calculation (see also FIG. 3B). In particular, it is
defined here that an aircraft yaw angle p changes the
heading of the aircraft by the amount cp. The rate of
change of the aircraft heading is identically dcp/dt. The
yaw angle ep may be used in a fashion similar to the above
to yield a more accurate calculation of the terrain faced
by an aircraft.
Referring to FIG. 5, an aircraft 134 is initially
along a flight path 136 towards an obstruction 132.
Lateral red, yellow, green, and black zones may be defined,
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analogous to the vertical ones above, and the same are
shown near the bottom of the figure. After a yaw rotation
of p to flight path 138, the colored zones are shifted. In
this case, the obstruction 132 remains in the red zone but
to a far less degree than previously.
The calculation to accomplish the displayed shift is
analogous to the above. In this case, however, the lateral
b' which enters the computation may be calculated to first
order by the yaw p multiplied by the range Z. Similarly,
for use in higher order computations, the lateral velocity
may be calculated to first order by the yaw rate dcp/dt
multiplied by the range Z.
In one embodiment of these calculations, the distance
A between the obstruction and the projected flight path may
be determined at a series of points along the flight path
and the result signal can be based on this distance. If
the distance is less than some predetermined number, the
alert signal can be displayed as a red area with respect to
the bearing of the obstruction.
Of course, the same will be performed automatically by
the sensors inputting relevant data as the aircraft
reorients its systems during a nonzero yaw. However, by
having a separate data input for yaw angle, the resident
software may update the information displayed automatically
and more rapidly than waiting for GPS and database
information to be updated via change of input data from
sensors, i.e., as the aircraft heading changes.
It will be clear that the calculation and analysis
above are the same no matter whether the aircraft is
banking left or right, i.e., whether a positive or negative
yaw is applied. Similarly, yellow, green, and black zones
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are present to the right of the aircraft, although these
are not shown in FIG. 5 for the sake of clarity.
This calculation may be more complicated than the b
calculation above, as yaw may not typically be expected to
be as constant as flight path angle. However, the
technique may still be used to at least eliminate certain
obstructions from causing alerts if the obstructions are
clearly not dangers due to the nonzero aircraft yaw.
Referring to FIG. 6, a flowchart is shown embodying a
method of the present invention. As shown, the method
starts (step 202) and a sensor measures data about a flight
path angle of ascent or descent (step 216) . Of course, the
same may well indicate, in the most general case, level
flight. The system then receives this data (step 204).
Altitude data (step 218) is then received from an altitude
sensor," such as an altimeter (step 206) . Xeff, i.e., the
effective altitude of the aircraft at a point projected or
predicted at each range point Z, may then be calculated
(step 208).
Prior to, contemporaneous with, or after this
calculation, a datum or data may be received regarding the
known terrain. Such a first datum may be obtained in part
by the aircraft location as determined by a navigation
technique, such as.GPS, or by another technique (step 214).
In this way, a comparison of the aircraft location and
height with known terrain features as received from a
database or look-up table (step 212) may be performed. In
other words, the local terrain may be compared to the
effective altitude (step 220) to result in the color scheme
(step 222) displayed to the pilot on the display screen 102
(step 224).
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Of course, it will be noted that various steps may be
taken out of the order given above. For example, the
calculation of 5 may well occur directly following the
completion of steps 204 and 206. Similarly, steps 204 and
206 may occur in the given or the reverse order as
described.
It should be noted that the above devices mentioned
are not necessarily exclusive of those that can be used.
The altimeter may be a radio altimeter, barometric
altimeter, GPS, or any other type of altitude sensor or
height indicator that may effectively measure the height of
the aircraft, i.e., a third datum, for the calculation.
Further, the calculation of S may involve a computation
employing the measured aircraft flight path, i.e., a fourth
datum, as determined by GPS or other such sensors.
The calculation steps 208, 220, and 222 may, occur by
the process disclosed above and at the various levels of
sophistication disclosed above. That is, the climbing or
descending flight path angle may be the only factor
considered, or higher order derivatives, as well as
considerations of the yaw and its derivatives, may also be
considered.
Referring to FIG. 7, a system-level schematic is shown
of a system that may embody the present invention. In
particular, the predictive altitude display 100 may accept
data inputs at an input/output interface 310 from at least
instruments functioning as an altimeter 302, an aid to
navigation 304, and a heading sensor 312, such as a
compass. The input/output interface 310 is shown
generally. The first through fourth inputs, i.e., altitude
of an aircraft, location of the aircraft, height and
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location of obstructions, and aircraft flight path,
respectively, may derive from a single device or from a
combination of devices. The first through fourth inputs
may further be input via the input/output interface 310 via
being at least a portion of a parallel data bus or as a
portion of a serial data stream.
The location of terrain may be achieved via comparison
of the known aircraft location, as determined by, e.g.,
GPS, with the terrain features noted in that vicinity by a
look-up table or database 311.
A measurement of the aircraft flight path V is then
made either as a calculation by a circuit or software
within the devices indicated above, or via separate
devices. For example, many altimeters can also measure the
vertical velocity component of flight path (v-'-), or as
shown in FIG. 3B, the component of flight path in the
direction x3r as the same is simply a first derivative of
the altimeter measurement with respect to time. Also, many
aids to navigation, such as certain GPS units, can also be
employed to measure lateral flight path, i.e., the vector
addition of the components x1 and x2 as shown in FIG. 3B,
or, if desired by the calculation, the component of lateral
flight path in the direction of a particular obstruction.
The compass 312 may be employed to measure the heading
of the aircraft and to thus orient the display. Of course,
given an appropriate measurement time, as is known, the aid
to navigation 304 or a different device may also be used to
measure the heading. As is clear from the teaching above,
while the flight path measurements are shown in FIG. 5 as
being within the altimeter 302 and the aid to navigation
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304, the same may be measured or computed outside of these
subsystems,
The components of flight path, as well as the
components of the aircraft location, can then be employed
to perform embodiments of the method of the invention as
described above. The same may calculate or generate a
result signal, indicative of an effective altitude Xeff,
also termed herein a projected height, of the aircraft at a
location of an obstruction or indeed at any point within
the range of the screen display. The result signal may
then be used to derive the appropriate pixel color array
for display to the pilot on the screen display.
It will be understood that the above description of a
Method and Apparatus for Predictive Altitude Display has
been with respect to particular embodiments of the
invention. While this description is fully capable of
attaining the objects of the invention, it is understood
that the same is merely representative of the broad scope
of the invention envisioned, and that numerous variations
of the above embodiments may be known or may become known
or are obvious or may become obvious to one of ordinary
skill in the art, and these variations are fully within the
broad scope of the invention. For example, while the
forward arc has been defined here as an arc of 70 , it is
understood that other forward arc angles could also be
used. Further, while finite values of elevation buffer
have been described, a elevation buffer could be equal to
zero in some circumstances. Even further, while the term
"computer" has been employed in the specification, it is to
be understood that a general-purpose microprocessor driven
computer is not necessary to run the programs or methods
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CA 02501908 2010-02-23
described here. A more limited chip design or circuit may be
employed to run the same, and the same may be preferable due
to the limited space available in standard avionics
components. Accordingly, the scope of the invention is to be
limited only by the claims appended hereto, and equivalents
thereof. In these claims, a reference to an element in the
singular is not intended to mean "one and only one" unless
explicitly stated. Rather, the same is intended to mean "one
or more". All structural and functional equivalents to the
elements of the above-described preferred embodiment that
are known or later come to be known to those of ordinary
skill in the art are expressly incorporated herein by
reference and are intended to be encompassed by the present
claims. Moreover, it is not necessary for an apparatus or
method to address each and every problem sought to be solved
by the present invention, for it to be encompassed by the
present claims. Furthermore, no element, component, or
method step in the present invention is intended to be
dedicated to the public regardless of whether the element,
component, or method step is explicitly recited in the
claims.
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