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Description  |
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FIELD OF THE INVENTION
This invention relates to moving map displays.
BACKGROUND OF THE ART
It is often desirable to provide to the operator of a moving vehicle,
typically an aircraft, a moving map display as a navigational aid, or to
show the topographical and other features of the terrain over which he is
or will be flying. This is particularly true for the pilot of an aircraft
where the terrain may be obscured by cloud cover or darkness. Some
advanced radar systems are capable of generating an image of the terrain
immediately surrounding the aircraft. However, the terrain radar display
contains only limited information and the radar image must be correlated
with a navigational map in order to provide the pilot with useful
information, such as labels identifying pertinent topographic features and
landmarks. Moving map displays have been developed that utilize film
strips that have been laboriously fabricated from many individual maps of
smaller areas, which when combined form the total film strip. Presently,
the means for storing maps to be displayed in moving map displays do not
include video signal storage means.
SUMMARY OF THE INVENTION
The inability of the prior art to provide a moving map display using stored
video signals is solved by my invention. In the present invention each map
segment is stored as a video signal on video signal storage means.
Position information from a navigation system is used to select the video
signals for the map segments which are required to display the area, in
the middle of which the vehicle is located. The video signals for the
selected map segments are read out of video signal storage in parallel. A
microprocessor controls video switching apparatus to select portions of
the signals read out to be combined to make up a new composite map frame
video signal used to display an area with the vehicle being located at the
middle thereof. The new composite map frame signal is continuously changed
or updated as the vehicle moves to keep the vehicle at the middle of the
display.
The capacity of video signal storage means such as a commercial video disk
is so large that a standard twelve inch disk can store fifty six thousand
map segments. This permits a single video disk to store different map
scales and overlay information for each map segment as desired by the
equipment operator. Other video signal storage means such as magnetic
drums, or other analog signal storage means may also be utilized.
The invention will now be described with reference to the accompanying
drawing where:
FIG. 1 is a system schematic block diagram of the present invention;
FIG. 2 represents a large map broken up into a number of map segments;
FIG. 3 is a blow-up of nine adjacent map segments from which a new map
segment is to be made;
FIG. 4 is a more detailed representation of four adjacent map segments,
video signals for which are stored on video signal storage means and
portions thereof are combined to form the video signal for a new composite
map segment; and
FIG. 5 shows a representation of video signals stored on video signal
storage means and how portions of them are combined to make up a composite
video signal for a new map segment.
DETAILED DESCRIPTION
In FIG. 1 is shown the schematic block diagram for my invention. In the
following description a video disk is used as the video signal storage
means storing raster scan format video signals for the map segments.
Navigation system 10 may be any one of the many navigation systems known
in the art that provide output information regarding the present position
of a vehicle or other craft on which navigation system 10 is located. In
addition to the output information from navigation system 10 being
displayed in some conventional well-known manner (not shown), the position
information is also used as an input to a switching arrangement such as a
microprocessor 11. Microprocessor 11 utilizes this information to look up
in memory 12 the track that is to be accessed by video disk player 13 that
has the video signal recorded thereon necessary to display a primary map
segment for the area in which the vehicle containing navigation system 10
and my novel moving map display is located. In addition, microprocessor 11
utilizes information in memory 12 to locate other tracks on the video disk
containing video signals for map segments adjacent to the primary map
segment. The finer details regarding storage of video signals for map
segments and the manner in which they are read out are described further
in this specification.
Video disk player 13 may be made up of one, two, or four commercial video
disk players operating in tandem or, preferrably, may be one video disk
player with two playback heads. The reason for two playback heads in the
preferred embodiment of video disk player 13 is to concurrently read out
video signals stored on two different tracks of the video disk. These
video signals are both applied to first video switch 14 which is under the
control of microprocessor 11 which also controls the second video switch
15. Microprocessor 11 controls video switches 14 and 15 to selectively
switch the video signal to delay circuits 16 and 17 and to summing
circuits 18, 19 and 20 to make up a new video signal which has vertical
and horizontal sync pulses added thereto. The sync pulses and other timing
signals are provided by timing pulse and waveform generator 21 which
operates synchronously with the video disk player using methods that are
well known in the art.
Turning now to FIG. 2, therein is shown a large map 30 broken up into a
plurality of rows and columns of map segments. No typical map information
is shown thereon to avoid cluttering up FIG. 2 and thereby detracting from
an understanding of the present invention. As may be seen in FIG. 2, there
are n columns by m rows of map segments making up a total of mn map
segments. The designations on some of these map segments are
self-explanatory.
In FIG. 3 is shown a blow-up of nine of the map segments shown in FIG. 2.
In operation, navigation system 10 provides information to microprocessor
11 indicating the position of the vehicle upon which navigation system 10
and my novel moving map display are located. By way of example, the
vehicle position is represented by the x on map segment n+4 in FIG. 3.
In order to show the position of the vehicle moving map display system
does not just display map segment n+4. Rather, a new map portion
represented by the bounds T, Q, G, and H is displayed. This requires that
portions of map segments, 3, 4, n+3, and n+4 be selected and combined to
make up the new composite map segment represented by the bounds T, Q, G,
and H. This is accomplished by the teaching of my invention.
In viewing FIG. 3, it is obvious that the map segments chosen to make up a
new composite map segment depend upon the position of the vehicle in the
area shown by primary map segment n+4. In the example just given the
vehicle is located within quadrant A of the map segment n+4 and,
therefore, portions of map segments 3, 4, n+3, and n+4 are required to
make up the new map segment. However, if the position of the vehicle were
in quadrant B of map segment n+4, portions of map segment 4, 5, n+4, and
n+5 would be required to make up the new map segment. In similar manner,
if the position of the vehicle were located within quadrant C in map
segment n+4 then portions of map segments n+3, n+4, 2n+3, and 2n+4 would
be required to make up the new map segment. Likewise if the position of
the vehicle were within quadrant D of map segment n+4 then portions of map
segments n+4, n+5, 2n+4, and 2n+5 would be required to make up the new map
segment in the center of which is displayed the position of the vehicle
represented by X. Thus, microprocessor 11 in the moving map display
system must first determine the primary map segment n+4 covering the area
in which the vehicle is located and then must determine which of the four
quadrants thereof in which the vehicle is located. This is accomplished
using look up tables stored in memory 12. The identity of the primary map
segment and the appropriate quadrant thereof are used to address memory 12
and the information read out of the memory identifies the position of the
four tracks on the disk.
With the example shown in FIG. 3, with the position of the vehicle being
located in quadrant A of map segment n+4, the video signals for map
segments 3, 4, n+3, and n+4 must be read out and the appropriate portions
thereof selected and combined to make up the video signal for the
composite map segment designated by the bounds T, Q, G, and H. In the
preferred embodiment of the invention the two playback heads of video disk
player 13 are initially positioned to concurrently read out the video
signals for map segments 3 and 4 are completely read out. The two playback
heads are then switched to the video disk tracks containing the video
signals for map segments n+3 and n+4 and the video signals for these two
map segments are read out during the next revolution of the video disk.
The playback heads are then repositioned to again read the video disk
tracks containing the video signals for map segments 3 and 4. This
switching and reading process is repeated for the video disk tracks
containing the video signals for map segments 3, 4, n+3, and n+4 until the
vehicle upon which the moving map display equipment is located moves to
another quadrant of map segment n+4 or another quadrant in one of map
segments 3, 4, or n+3. At that time microprocessor 11 determines which new
four map segments are to be read out and in what order to continue
generating a video signal for the composite map segment showing the
position of the vehicle at the center thereof. As the video disk player
art advances it is apparent that the speed at which the read out head or
other device means can switch from track to track will decrease. When the
art has thus advanced, then only one read out head will be required that
will be able to jump from one track to another track, and possibly across
the whole disk, without sufficient delay to hinder the operation of my
invention. It is also possible that new storage means will replace video
disk players but will be able to function with my invention. However, with
the present state of the art there are finite periods of time required to
switch the read heads from one video disk track to another. To overcome
this switching problem two read heads are presently utilized in the
present preferred embodiment. No matter which four map segments are
selected by microprocessor 11, as required to make up a new composite map
segment, the four chosen map segments are recorded on four adjacent tracks
on the video disk. The use of two read heads each of which only has to
move from one track to an adjacent track minimizes track switching time
delays that are detrimental to the operation of the present invention.
Utilizing the data compression techniques disclosed immediately hereinafter
the number of times a given map segment must be recorded on a video disk
is minimized. Other data compression techniques may also be utilized. For
example, when the vehicle is located within quadrant A of map segment n+4,
map segments 3, 4, n+3, and n+4 are read out in that order. It should be
noted, however, that when the vehicle is located in quadrant C of map
segment 4, the same four map segments are read out in the exact same
order. When the vehicle is located in quadrant D of map segment 3, or in
quadrant B of map segment n+3, again the same four map segments are read
out in the same order. Thus, map segments 3, 4, n+3 and n+4 are recorded
on four adjacent tracks of a video disk and when microprocessor 11
determines that the vehicle is in one of the aforementioned map segments
and quadrants, the same group of four video disk tracks are read out.
Turning now to FIGS. 3 and 4, portions of the video signals of map segments
3, 4, n+3, and n+4 are selected to make up the new video signal for the
composite map from QTHG. Referring also to FIG. 1, the new video signal
for map frame QTHG is obtained by switching signals from the video disc
player 13 with the first and second video switches 14 and 15. The new
video signal for from QTHG is composed by switching the signals from the
video disc player 13 so as to effect a transformation of coordinates from
the coordinates of frames 3, 4, n+3, and n+4 to the coordinate of frame
QTHG. Using simple mathematical relationships, and knowing the present
position of the vehicle from the navigation equipment as represented by X
, one it can mathematically determine the corners T, Q, G, and H as shown
in FIG.3. As part of the above, it is also a simple mathematical
calculation to determine on which scan lines and how far across particular
scan lines the video signals being read off a track of the video disk must
be selected or rejected to make up the new video signal for the composite
map segment. For example, with references to FIG. 4, initially the two
record heads are concurrently reading the two tracks on the video disk
which contain the video signals for map segments 3 and 4. The video
signals being read off tracks 3 and 4 represent a raster scanning beam
starting at the upper left hand corners of the squares representing map
segments 3 and 4 and sweep from left to right across the block and repeat
this left to right sweep starting at the top of the block and progressing
down to the bottom of the blocks in the conventional television raster
format.
With the particular example represented in FIG. 4, a new composite video
signal is to be made up for the new map segment having the X at its
center and requiring portions of the video signals of map segments 3, 4,
n+3, and n+4 to make up same. After the microprocessor 11 determines from
the navigation system input that the vehicle upon which the moving map
display equipment is located lies in quadrant A of map segment n+4, it
uses this information to address memory 12 from which it reads the video
disk track addresses for the video signals for map segments 3, 4, n+3, and
n+4. Signals are then sent to video disk player 13 causing the read heads
or other read mechanisms to initially position the two read heads on the
tracks containing the video signals for map segments 3 and 4. As the video
disk completes one full revolution the video signals required to
completely display map segments 3 and 4 have been read off the disk in
parallel and are forwarded to first video switch 14 so that portions
thereof may be selected under the control of microprocessor 11. The read
heads are then positioned to read the tracks containing the video signals
for map segments n+3 and n+4 during the next revolution of the video disk.
More particularly, as the video signals for map segments 3 and 4 are read
off the disk in parallel they are initially blocked at first video switch
14 (see FIG. 1) as the signal figuratively sweeps from left to right and
from top to bottom before the scan lines simultaneously sweeps starting at
points P and S for these two map segments. However, as the video signals
read off the video disk for map segments 3 and 4 come to the scan lines
starting at points P and S on FIG. 4 portions of these signals are
required to make up the new map segment. As the video signal is read off
the disk for the remainder of map segment 3 from point P to point Q the
signal read off the video disk is blocked at switch 14 but during the
period between the points Q and R for each remaining sweep the signal read
off the disk is passed through video switch 14. For the period of time
between points R and S for each remaining sweep the signal for map segment
3 is blocked as it contains horizontal retrace signals which are not
required. During this same period of time for the complete scan lines
between points P and S the second head is reading the video signal for map
segment 4 between points S and V. As switch 14 is disabled from passing
through the portion of scan lines between points P and Q for map segment 3
it is enabled to pass through the video signal for map segment 4 between
points S and T. Likewise, when disabled from passing video signal for map
segment 3 between points Q and R it is disabled from passing signal
between points T and U.
From a time flow of events, however, the signal that appears first at the
output of switch 14 is that portion of the scan line of map segment 4
between points S and T and immediately thereafter that portion of the
signal for the scan line of map segment 3 between points Q and R. The time
order in which these signals appear is backwards and must be corrected
for. These two signal segments are placed in the proper time sequence in
the following manner. The video information for two adjacent raster scan
lines, ST and S.sub.1 T.sub.1 for example, is essentially identical. Video
switch 14 is thus enabled to pass the video information to a first scan
line between the points or time period represented by Q and R. Video
switch 14 is then enabled to pass the video information for the segment
S.sub.1 T.sub.1 during the second or next scan line. In this manner, the
video information for the period QR is placed before the video information
for the period ST for a scan line of the new map segment. If the video
information on S.sub.1 T.sub. 1 is significantly different enough to cause
difficulty this can be accommodated by recording frames 4 and n+4 so that
they are offset by one at the time the video disk is made.
One other problem now arises by operating in this manner. Although the
video information for the period QR now occurs prior to the video
information for the period ST within a single scan line of the new map
segment the time period RS has not been taken into account. In a time flow
of events the video signal for the period QR occurs first, then the period
RS from which the horizontal blanking information has been blocked occurs,
followed by the video information for the period ST. The period RS in the
middle of the new frame or segment must be deleted in the manner described
with reference to FIGS. 1 and 5.
In FIG. 5 at lines (A) and (B) are seen representative video signals for
two horizontal scan lines read off two video disk tracks respectively
designated map segment 3 and map segment 4. The same letter designations
are used on FIG. 5 as used in FIG. 4 to represent portions of the video
signal and the horizontal retrace signal. That is, the horizontal retrace
signals with blanking pulse and other color burst information occur in the
periods RS and UV. The time periods PQ, QR, ST, and TU are also shown. The
video signal for the two scan lines of one track are shown identical but
in reality this may not be so. As previously described, and with reference
to line (A) of FIG. 5, video switch 14 is first disabled so as not to pass
the video information occuring in time period PQ, but is at the same time
enabled to pass the video signal occuring in the time period ST for map
segment 4 in line (B). Thereafter, video switch 14 is enabled to pass the
video signal in line (A) of FIG. 5 during the period QR but at the same
time is disabled from passing the video signal during the period TU for
map segment 4 in line (B). Video switch 14 switches the video signal for
the period QR of map segment 3 through delay circuit 16, the delay of
which is equal to the horizontal retrace time, RS, and thence through
video switch 15 to summing circuit 18. Video switch 14 is controlled by
microprocessor 11 to pass the video signal for the period ST of map
segment 4 directly to the second input of summing circuit 18. The output
from summing circuit 18 is the video wave form shown in line (C) of FIG. 5
and has the desired effect of removing the horizontal retrace period RS
that would occur in the middle of the mixed video signal portions. The
reformated video signal shown in line (C) which is the output from summing
18 is passed through delay circuit 17, the delay of which is equal to the
vertical retrace time, to summing circuit 19, and then to summing circuit
20 to be mixed with new horizontal retrace information to make up the
video output signal for the new map segment. Timing pulse and wave form
generator 21 is the clock circuit for microprocessor 11 which in
conjunction with timing track signals from video disk 13 helps
microprocessor 11 determine when to operate video switches 14 and 15. In
addition, microprocessor 11 causes pulses to be output from circuit 21 to
the other two inputs of summing circuit 20 to add in horizontal retrace
pulse and color burst information seen in FIG. 5 (D). The operation of the
circuits in handling vertical retrace information is described
hereinafter. As the read heads of video disk player 13 are reading the
last raster scan line of both map segments 3 and 4 before vertical retrace
signals, microprocessor 11 is aware of this due to the timing information
it is receiving from circuit 21. Microprocessor 11 enables video switch 14
to pass the video signal for map segment 4 during the time period ST for
the last scan line of map segment 4 but at this time disables video switch
14 from passing video signal for the subsequent period QR. Following the
last reaster scan line of both map segments 3 and 4 the two read heads are
reading out vertical blanking, vertical sync pulses and other control
signals during the vertical retrace time as known in the art. Following
the vertical retrace period microprocessor 11 is enabling and disabling
switch 14 to pass through those portions of the video signals for map
segments n+3 and n+4 in the manner just described for map segments 3 and 4
to finish making up the video signal for the new map segment. However, the
vertical retrace period just mentioned will cause a band to appear across
the map display. This band is deleted in a manner similar to that in which
the horizontal retrace information was deleted. The reformated video
signal for that portion of the new map segment made up of video signals
from map segments 3 and 4 has been passing through delay line 17 to
summing circuit 19 up to this time. At this point in time, microprocessor
11 operates video switch 15 to route the signals in a different fashion.
That portion of the video signal coming from map segment n+3 is switched
through delay circuit 16 to video switch 15 which then routes the signal
directly to summing circuit 19 rather than to circuits 17 and 18 as done
up to this point in time. Video switch 14 switches the portion of the
video signal from map segment n+4 completely past circuits 15, 16, 17 and
18 to summing circuit 19. Thus, the signal output from summing circuit 19
is a video signal deleting the vertical and horizontal retrace pulses and
other sync signals as originally read off the video disk. Summing circuit
20 then is used to add in sync signals such as horizontal and vertical
sync and color burst information to the video signal to make up the
complete composite video signal for the new map frame segment.
In an alternative embodiment of the invention, in each of the groups of
four tracks/map segments previously described, the video signal for two of
the four tracks is delayed on the disk by a time period equal to the
horizontal retrace time. Referring to FIG. 4, the data stored for map
segments 3 and n+3 is delayed by a period equal to the horizontal retrace
period. The result is that the signal read by the first read head reading
map segment 3 doesn't start reading the portion of video signal originally
starting at the time represented bypoint Q, but rather starts reading that
portion of video signal by an amount of time that is equal to the
horizontal retrace time later or an interval represented between points R
and S. The result is that the portion of video signal from the first read
head that previously terminated at the point R now terminates at the point
S, just as the signal from map segment 4 commences. This eliminates the
need for horizontal retrace delay line 16, in order to make the signal
portions contiguously sequential.
Another variation of this idea is not to shift the signal on the disk but
to physically move or offset the first read head to accomplish the same
delay. Similarly, at the appropriate moment in time both heads may be
mechanically or electronically offset to effectively add or remove the
vertical delay line 17 in FIG. 1.
Using the techniques described above map overlay information for each map
segment may be stored on the video disk and portions thereof may be read
off and combined with the video signal for the composite map segment. The
composite map segment displayed would have the overlay information
thereon.
With the large capacity of the video disk, map segments making up maps of
different scales may be stored and in response to a scale indication from
the operator of the moving map display the map segments of the indicated
scale are selectively read out to make up the composite map segment
displayed on the moving map display.
It would be obvious to one skilled in the art that other approaches may be
used to reverse the time order of appearance of the video signal portions
in the time periods QR and ST. For example, the video signal for the time
period QR may be input to an analog shift register such as a charge
coupled device (CCD) shift register and the microprocessor taps this shift
register at an appropriate point to remove the signal therefrom so that it
appears immediately following time period ST. The digital signal would
then be reconverted to analog and be mixed with the other analog signal to
make up the video signal for the new map segment.
While what has been described above is the preferred embodiment of the
invention it would be obvious to those skilled in the art that many
changes and modifications may be made thereto without departing from the
spirit and scope of the invention. For example, as the video disk player
art advances the read mechanisms therein may be able to switch between
tracks fast enough to eliminate the present requirement for two or more
playheads and thereby eliminate the need to organize map segments on
adjacent tracks as previously described.
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