Aircraft docking guidance system which takes position reference in anti-collision light of aircraft

A plurality of image pickup devices are set on the ground to pick up images of an anti-collision light located on an aircraft to be guided. A position reference producing section produces a signal representing a position reference of the aircraft in accordance with picked-up image signals from the plurality of image pickup devices. A display data producing section produces at least one of direction information and distance information as guidance information to be provided to pilots of the aircraft in accordance with the signal representing the position reference of the aircraft which is supplied from the position reference producing section. A display unit displays at least one of the direction information and distance information from the display data producing section at a position on the ground where the pilots can see and recognize the information.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an aircraft docking guidance system which 
provides pilots of taxing planes with data concerning distance and azimuth 
(direction) during movement across airport aprons to the parking spot. 
More particularly, this invention relates to an aircraft docking guidance 
apparatus for calculating a deviation from an approach line and a distance 
from a stop point to the nose gear in a parking spot by using a picked-up 
image of an anti-collision light (ACL) located on the upper fuselage of 
all aircraft as a position reference, and visually displaying the 
calculation results to a pilot as azimuth (direction) information and 
distance information by means of a display unit on the ground, thereby 
accurately guiding the aircraft from airport aprons to the parking spot. 
2. Description of the Related Art 
A conventional aircraft docking guidance apparatus is designed to provide 
azimuth (direction) and distance information by utilizing an optical 
technique. In this technique, however, since the parallax varies among 
pilots depending on the loading capacities of aircraft, sufficiently 
precise azimuth (direction) information cannot be obtained. 
More specifically, in the conventional technique, of various types of 
schemes, azimuth (direction) information is obtained by mainly using the 
parallax of a pilot by optical applications, and a deviation from an 
approach line is displayed on a display unit installed on the ground. For 
this reason, proper azimuth (direction) information can be obtained at the 
captain's seat, but cannot be obtained at the co-pilot's seat. That is, 
only the captain can pilot the aircraft. 
In the conventional technique, distance information is obtained by mainly 
using a sensor buried underground below an approach path. According to 
this technique, when the passage of wheels of an aircraft is detected, a 
remaining distance is displayed on a display unit. In this distance 
information display technique, however, the installation and maintenance 
of this sensor interfere with flight operations of aircraft. 
Furthermore, in the above-described azimuth and distance information 
display techniques, it is difficult to control different types of 
aircrafts with respect to the sam parking spot. 
As another guidance technique, a distance measurement technique based on a 
laser is available. This technique, however, can only be applied to 
limited types of aircracts, because the reflectivity of a laser beam with 
respect to dark colors is low. In addition, it is difficult to properly 
use this technique in all kinds of weathers. 
SUMMARY OF THE INVENTION 
It is, therefore, an object of the present invention to provide a new and 
improved aircraft docking guidance system which takes a position reference 
in an anti-collision light of an aircraft, in which the position reference 
of the aircraft is obtained on the basis of picked-up image signals 
obtained by picking-up the anti-collision light of the aircraft by means 
of a plurality of image pickup devices on the ground, and azimuth 
(direction) information and distance information are generated in 
accordance with the position reference to be displayed on a display unit 
on the ground, thereby providing proper information not only to the 
captain's seat but also to the co-pilot's seat without requiring burying 
of a sensor in an apron, and allowing not only a pilot but also a co-pilot 
to accurately guide the aircraft to a parking spot without the support of 
ground staff. 
According to one aspect of the present invention, there is provided an 
aircraft docking guidance apparatus comprising: 
a plurality of image pickup devices, set on the ground, for picking up 
images of an anti-collision light located on an aircraft to be guided; 
position reference producing means for producing a signal representing a 
position reference of the aircraft in accordance with picked-up image 
signals from the plurality of image pickup devices; 
display data producing means for producing at least one of azimuth 
(direction) information and distance information as guidance information 
to be provided to pilots of the aircraft in accordance with the signal 
representing the position reference of the aircract which is supplied from 
the position reference producing means; and 
a display unit for displaying at least one of the azimuth (direction) 
information and distance information from the display data producing means 
at a position on the ground where the pilots can see and recognize the 
information. 
More specifically, in order to achieve the above object, the present 
invention is characterized by comprising two charge coupled device (CCD) 
cameras, extractors, a tracker, an arithmetic processing unit, and a 
display unit constituted by a display lamp, which are arranged in the 
forward direction of an aircraft which approaches an apron, and an 
operation unit installed at an arbitrary position at which an operator on 
the ground can easily operate the operation unit. 
According to the above-described arrangement, in the aircraft docking 
guidance apparatus of the present invention, an anti-collision light (to 
be referred to as an ACL hereinafter) located on an upper fuselage of each 
aircraft which is approaching the apron is imaged by the two CCD cameras, 
and the extractors extract only ACL red flashes from the picked-up image 
outputs. The tracker tracks the two color extraction images, and obtains 
the center of gravity of each ACL image. On the basis of the obtained two 
points, the tracker calculates one point of a three-dimensional space 
coordinate system defined on the basis of on a parking spot on the 
approach line as the origin. That is, the position of the ACL is 
three-dimensionally measured as the position reference of the aircraft, 
and tracking is performed with respect to the position reference. The 
arithmetic processing unit stores relative position data of ACLs and nose 
gears, approach line data, and parking spot data, which vary depending on 
aircraft types, in a read only memory (ROM) in advance. In the first step, 
the type of an approaching aircraft is selected by the operation unit. 
When the two CCD cameras image an ACL, the arithmetic processing unit 
calculates a deviation from the approach line as azimuth information and 
the distance from the parking spot to the nose gear as distance 
information, and displays the output information on the display lamp. 
In order to achieve the above object, according to another aspect of the 
present invention, there is provided an aircraft docking guidance 
apparatus comprising an azimuth (direction) measuring image pickup device, 
installed in a forward direction of an aircraft which is approaching an 
apron, for picking up an image of an anti-collision light located on the 
aircraft which is approaching the apron, a distance measuring image pickup 
device, installed in a direction to face a side surface of an aircraft 
which is approaching the apron, for picking up an image of the 
anti-collision light of the aircraft which is approaching the apron, a 
measuring device for extracting an anti-collision light image from 
picked-up image outputs from the distance measuring image pickup device 
and the azimuth (direction) measuring image pickup device, calculating a 
difference between the center of the anti-collision light image and an 
aircraft approach line to obtain azimuth (direction) information, and 
calculating a distance from the center of the anti-collision light to a 
parking spot of the aircraft to obtain distance information, and a display 
unit for receiving and displaying the azimuth (direction) information and 
the distance information from the measuring device. 
With the above-described arrangement, an ACL of an aircraft which is 
approaching the apron is imaged by the azimuth (direction) measuring image 
pickup device installed in the forward direction of the aircraft and by 
the distance measuring image pickup device installed in the direction to 
face a side surface of the aircraft, and an ACL image is extracted from 
picked-up image outputs from the respective image pickup devices. The 
difference between the center of the ACL and the approach line and the 
distance to the parking spot are calculated by the measuring device. The 
former information is displayed on the display unit as azimuth (direction) 
information; and the latter information, as distance information, thereby 
accurately guiding the aircraft to the parking spot. 
According to still another aspect of the present invention, there is 
provided a method for providing a docking guidance to an aircraft, the 
method comprising the steps of: 
picking up images of an anti-collision light located on an aircraft by 
using a plurality of image pickup devices; 
producing a position reference of the aircraft on the basis of picked-up 
image signals from the plurality of image pickup devices; and 
producing at least one of azimuth (direction) information and distance 
information as the docking guidance in accordance with the position 
reference of the aircraft and providing the information to the aircraft 
through a display unit on the ground. 
Additional objects and advantages of the invention will be set forth in the 
description which follows, and in part will be obvious from the 
description, or may be learned by practice of the invention. The objects 
and advantages of the invention may be realized and obtained by means of 
the instrumentalities and combinations particularly pointed out in the 
appended claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Reference will now be made in detail to the presently preferred embodiments 
of the invention as illustrated in the accompanying drawings, in which 
like reference characters designate like or corresponding parts throughout 
the several drawings. 
Embodiments of the present invention will be described with reference to 
the accompanying drawings. 
FIG. 1 shows the system function of an aircraft docking guidance apparatus 
according to the first embodiment of the present invention. FIG. 2 shows 
the overall arrangement of the apparatus. An azimuth (direction) measuring 
image pickup device, e.g., a CCD camera 1, is set on the ground in the 
forward direction of an aircraft 9 at a position above an extension line 
of an aircraft approach line 6 formed on an apron. The CCD camera 1 picks 
up an image of an anti-collision light (ACL) 3 located on an upper 
fuselage of the aircraft 9 which is approaching the apron. Upon reception 
of an azimuth (direction) picked-up image output from the CCD camera 1, a 
measuring device 7 on the ground extracts a red image from a red flash 
generated by the ACL 3 through a color identifying section of the 
measuring device 7. At the same time, the coordinates of the center of the 
image are obtained by an operating section of the measuring device 7. 
According to the operation procedure of the apparatus of this embodiment, 
a switching operation is performed first through an operation panel 8 on 
the ground to select the type of approaching aircraft 9. Aircraft type 
data, data of the approach line 6, and parking spot data of each type of 
aircraft are stored in the operating section of the measuring device 7. 
Upon the above-mentioned switching operation, data of a corresponding 
aircraft type is selected. 
The measuring device 7 obtains the difference between the center of the ACL 
3, which is obtained by the operating section, and the approach line 6 as 
azimuth (direction) information by using the operating section, and 
displays the azimuth (direction) information on a display unit 4 on the 
ground. 
If left and right coordinate values with reference to the approach line 6 
are set to be -2,560.ltoreq..times..ltoreq.2,550, an azimuth (direction) 
precision of 2.1 cm is obtained at a point 200 m from the CCD camera 1 
when the angle of field of view of the CCD camera 1 is .+-.15.degree.. 
A distance measuring image pickup device, e.g., a CCD camera 2, is set on 
the ground at one side of the approach line 6 (facing a side surface of 
the aircraft 9 which is approaching the apron). The CCD camera 2 picks up 
an image of the ACL 3 on the upper portion of the aircraft 9. Upon 
reception of a distance picked-up image output from the CCD camera 2, the 
measuring device 7 extracts a red image from the red flash generated by 
the ACL 3 through the color identifying section. At the same time, the 
coordinates of the center of the image are obtained by the operating 
section of the measuring device 7. The measuring device 7 obtains the 
distance from the center to the parking spot as distance information 
through the operating section, and displays the distance information on 
the display unit 4 on the ground. 
Assume that the CCD camera 2 is set on one side of the approach line 6 by 
using the line 6 as a reference, and the approach line 6 is set in the 
field of view of 100 m. In this case, if distance coordinate values are 
set to be -2,560.ltoreq..times..ltoreq.2,550, a distance precision of 2.0 
cm is obtained. 
As described above, in the aircraft docking guidance apparatus according to 
the first embodiment of the present invention, an ACL located on an upper 
fuselage of each an aircraft is imaged by the azimuth (direction) and 
distance measuring CCD cameras, and the difference between an approach 
line and a parking spot is provided as azimuth (direction) information by 
the measuring device on the basis of approach line, parking spot, and 
aircraft type data stored in advance, while the horizontal distance 
between the center of the ACL to the parking spot is provided as distance 
information. 
According to the first embodiment of the present invention, since the 
azimuth (direction) measuring CCD camera is set on the extension line of 
the approach line, and the distance measuring CCD camera is set on one 
side of the approach line, an accurate deviation from the approach line 
and an accurate distance to the parking spot can be provided as azimuth 
(direction) and distance information, respectively. 
As described above, according to the first embodiment, since an ACL located 
on an upper fuselage of each aircraft is used as a position reference of 
the aircraft, the position reference can be reliably imaged by the two CCD 
cameras installed on the ground even at night or in bad weathers. In this 
arrangement, the center of the ACL is obtained by color extraction in real 
time, and azimuth (direction) numerical coordinates and distance numerical 
coordinates are obtained by tracking the center of ACL upon movement of 
the aircraft, thereby displaying the obtained information on the display 
unit on the ground as accurate azimuth (direction) and distance 
information. With this display, not only a pilot but also a co-pilot can 
accurately stop the aircraft at the parking spot without the aid of 
guidance personnel stuff on the ground. 
The second embodiment of the present invention will be described below with 
reference to the accompanying drawings. FIGS. 3A and 3B show the system 
function of a guidance apparatus according to the second embodiment, 
respectively. FIG. 3C shows the display unit of FIG. 3B. FIG. 4 shows the 
overall arrangement of the apparatus according to the second embodiment. 
FIG. 5 shows a color space and ACL extraction. FIGS. 6A and 6B 
respectively show a two-dimensional coordinate system on an ACL extraction 
frame and an enlarged ACL image. FIGS. 7A and 7B are plan and side views 
showing a three-dimensional space coordinate system. As shown in FIGS. 3A 
and 3B, and FIG. 4, in this embodiment, a display unit 11 is installed on 
the ground in the forward direction of an aircraft 13 at a position above 
the extension line of an aircraft approach line 12 formed on an apron. A 
red flash generated by an ACL 14 located on an upper fuselage of an 
aircraft approaching the apron is picked up by CCD cameras 15 and 16 
arranged at the same position as that of the display unit 11 at a 
predetermined interval to be located on both sides of the approach line 
12. 
Video outputs from the CCD cameras 15 and 16 are respectively supplied to 
extractors 17 and 18. The extractors 17 and 18 extract only red images 
from the red flash generated by the ACL 14. The principle of color 
extraction will be described below. 
An arbitrary color is represented by a combination of three colors R (red), 
G (green), and B (blue). If, therefore, video signals representing 
brightness are respectively represented by R, G, and B, a signal Y 
representing the brightness of a color is given by Y=R+G+B. 
In this case, an arbitrary color is expressed by using three-dimensional 
signals (R-Y), (B-Y), and Y, instead of using the video signals R, G, and 
B, as shown in FIG. 5. 
On a color space constituted by the (R-Y) axis, the (B-Y) axis, and the Y 
axis, the extractors 17 and 18 set the upper and lower limit values of the 
(R-Y) and (B-Y) axes representing hues, respectively, in correspondence 
with the hues of a red flash from the ACL, and extract ACL images within a 
range, on the Y axis, corresponding to the set range. More specifically, 
since the Y axis represents lightness, extractors 17 and 18 output 
monochromatic video signals in such a manner that ACL images extracted on 
the Y axis are white, and other portions are black. 
A tracker 19 tracks the two color extraction images extracted in the 
above-described manner, and obtains the center of gravity of each ACL 
image. On the basis of the obtained two points, the tracker 19 calculates 
one point of a three-dimensional space coordinate system defined on the 
basis of a parking spot on the approach line 12 as the origin. That is, 
the position of the ACL 14 is three-dimensionally measured as the position 
reference of the aircraft 13, and tracking is performed with respect to 
the position reference. 
In this case, the tracker 19 obtains the coordinates of the center of 
gravity of each ACL image from a two-dimensional coordinate plane having a 
coordinate value of 5120 in the horizontal direction (x axis) and a 
coordinate value of 4800 in the vertical direction (y axis), as shown in 
FIGS. 6A and 6B. Therefore, in the horizontal direction, a resolution of 
about 1 mm is obtained with respect to a field of view of 5 m. 
The tracker 19 calculates the center of gravity of the ACL 14 every 1/30 
seconds, and performs position measurement by using a three-dimensional X, 
Y, and Z coordinate system set on the basis of the coordinates of the 
center of gravity of the ACL 14 imaged by each of the two cameras, as 
shown in FIGS. 7A and 7B. 
An arithmetic processing unit 20 calculates the difference between the ACL 
14 and the approach line in the horizontal direction as azimuth 
(direction) information on the basis of aircraft type data input from an 
operation unit 23 and the position measurement data from the tracker 19. 
In addition, the arithmetic processing unit 20 calculates the distance 
from a parking spot 21 to a nose gear as distance information. The 
arithmetic processing unit 20 then displays the azimuth (direction) and 
distance information on a display lamp 22 as shown in FIG. 3C, for 
example. 
In FIG. 3C, the display lamp 22 includes a distance displaying portion 22a, 
an azimuth (direction) displaying portion 22b and the other displaying 
portion 22c for displaying information such as a kind of aircraft. 
In this case, the arithmetic processing unit 20 stores relative position 
data of ACLs and nose gears, approach line data, and parking spot data, 
which vary depending on aircraft types, in a ROM in advance. In the first 
step, the type of approaching aircraft is selected by the operation unit 
23. When the two CCD cameras 15 and 16 image an ACL, the arithmetic 
processing unit 20 calculates a deviation from the approach line as 
azimuth (direction) information and the distance from the parking spot to 
the nose gear as distance information, and displays the output information 
on the display lamp 22. 
According to the guidance apparatus of the second embodiment of the present 
invention, therefore, an accurate deviation from an approach line and an 
accurate distance to a parking spot can be provided as azimuth (direction) 
and distance information, respectively. 
As has been described above, according to the second embodiment of the 
present invention, since an ACL located on an upper fuselage of each 
aircraft is used as a position reference of the aircraft, the position 
reference can be reliably imaged by the two CCD cameras installed on the 
ground even at night or in bad weathers. In this arrangement, the center 
of the ACL is obtained by color extraction in real time, and the center of 
ACL is tracked upon movement of the aircraft by three-dimensional 
measurement, thereby displaying high-precision azimuth (direction) and 
distance information on the display unit on the ground. With this display, 
not only a pilot but also a co-pilot can accurately stop the aircraft at 
the parking spot without the aid of guidance personnel staff on the 
ground. 
Additional embodiments of the present invention will be apparent to those 
skilled in the art from consideration of the specification and practice of 
the present invention disclosed herein. It is intended that the 
specification and examples be considered as exemplary only, with the true 
scope of the present invention being indicated by the following claims.