PROCEDE POUR REPRESENTER DES IMAGES RADAR D'UNE ZONE DE CIBLE A SURVEILLER

METHOD FOR DISPLAYING RADAR IMAGES OF A TARGET REGION TO BE MONITORED

Abrégé français

Selon l'invention, un système radar couvrant une zone cible à surveiller, telle qu'un aéroport, un port maritime ou un port fluvial, génère des images radar dans la phase d'approche. Ces dernières montrent la zone cible à surveiller, sous forme d'une image prise depuis la position du système radar en mode d'approche. Des images optiques de la zone cible sont superposées, à intervalles répétés et au moyen d'un système de traitement de données embarqué, sur les images radar de ladite zone cible radioralliée générées à l'aide du système radar pendant la phase d'approche. Les images combinées de la zone cible obtenues par superposition des images radar et des images optiques sont représentées en continu. En outre, grâce au système de traitement de données embarqué, des images optiques, incluant éventuellement des images couleur, de la zone cible à surveiller et mémorisées dans ledit système de traitement de données sont insérées, à intervalles prédéfinis, en arrière-plan des images radar dont les dimensions ont été adaptées en fonction de celles des images optiques.

Abrégé anglais

According to the invention a radar system covering a target area to be
monitored such as an airport, seaport or river port, generates radar images in
the approach phase. Said radar images show the target area to be monitored as
an image taken from the position of the approaching radar system. Over the
radar images of the target area being approached generated by means of the
radar system during the approach phase optical images of the same target area
are superimposed at repeated intervals by means of an on-board data processing
system. The combination images of the target area obtained by superimposing
radar images and optical images are represented continuously. In addition, by
means of the on-board data processing system optical images, possibly
including colour images, of the target area to be monitored and stored in the
data-processing system are at predefined intervals placed as background to
radar images the dimensions of which have been adjusted in line with those of
the optical images.

Revendications

CLAIMS
1. A method for displaying radar images that have been generated by
a radar system, which is carried by a platform and detects a target region to
be
monitored, such as an airport, a seaport or a river harbor, in the approach
phase
with the use of a data-processing system, the images depicting the target
region
to be monitored as a representation from the viewing position of the
approaching
radar system, characterized in that, with the aid of the platform-borne
data-processing system, optical images of the selected target region, the
images
being stored in this platform-borne data-processing system, are superposed in
repeating time intervals aver the radar images of the same region, which are
generated by the radar system during the approach phase, and combination
images of this target region, which are obtained through the superposing of
radar
with optical images, are displayed continuously.
2. The method according to claim 1, characterized in that, in
predetermined time intervals, the stored optical images of the target region
to be
monitored are sublayered as the background for radar images, which have been
correspondingly adapted in their dimensions, with the aid of the platform-home
data-processing system.
8

3. The method according to claim 1, characterized in that, in
predetermined time intervals, the stored color optical images of the target
region
to be monitored are sublayered as the background for radar images, which have
been correspondingly adapted in their dimensions, with the aid of the
platform-borne data-processing system.
4. The method according to one of claims 1 through 3, characterized
in that all back-scattered paints of stationary elements/targets of a scene
that are
likewise present in the optical images ate gated out of the radar images, and
only
the back-scattered points of targets that are not present in the optical
images are
displayed in the sublayered optical images.
5. The method according to one of claims 1 through 3, characterized
in that all back-scattered points of stationary elements/targets of a scene
are
gated out of the radar images, and only the back-scattered points at mobile
targets are displayed in the sublayered optical images.
6. The method according to claim 5, characterised in that targets that
have been detected by the radar system, but are not present in the optical
images, are displayed in color.
9

7. The method according to claim 5, characterized in that only mobile
targets that have been detected by the radar system are displayed in color.
8. The method according to claim 5, characterized in that stationary
and mobile targets that have been detected by the radar system, but are not
present in the optical image, are displayed in different colors.
9. The method according to claim 5, characterized in that different
mobile targets that have been detected by the radar system are displayed in
different colors.
10. The method according to one of the foregoing claims, characterized
in that a specific section of the selected target region of the radar images
superposed over the optical images is displayed with the highest-resolution
made.
11. The method according to one of the foregoing claims, characterized
in that only the central portion of the radar images superposed over the
optical
images is displayed with the highest-resolution mode. and the edge regions are
displayed with a lower-resolution mode.
10

12. The method according to one of the foregoing claims, characterized
in that the optical images are displayed at a lower repetition rate than the
images
obtained with the radar system.
13. The method according to claim 12, characterized in that images
that have been obtained by the platform-borne radar system and processed with
the likewise platform-borne data-processing system are displayed at a
repetition
rate in the order of magnitude of about 10 to 100 Hz.
14. The method according to claim 12, characterized in that a plurality
of consecutive optical images is interpolated at a low repetition rate.
15. The method according to claim 1, characterized in that the radar
system is formed by a so-called forward-looking radar.
16. The method according to claim 1, characterized in that the radar
system is formed by a so-called sector-imaging radar.
11

Description

Nuv-02-2000 12:01 From-BERESKIN ~ PARR CA 02322378 2000-os~l6 T-653 P.003/013
F-734
DEscR#PT~oN
MPTHOD FOR D#SPt-AYlNG RADAR tMAGES OF A TARGET REGION TO BE
MONITORED
Tl=CHNICAI. FtEt-D
The invention felates to a method for displaying radar images of a target
region to be monitored, such as an airport, a seaport or a river har'bpr_
1 o PRIOR ART
Such target regions are generally detected by a monitoring system carried
py a platform, such as an airuaft, a ship or the like, the system ~mprising a
radar system and a data-processing system tf a platform-borne radar system of
this type detects, for exarr~ple. an airfeld, particularly a runway, or the
entryway
to a seaport or river harbor, backscatter signals of varying intensity are
4isplayed
on the monitors) of the radar system.
A radar disp#ay of this type includes regions that are shown with different
gray-scale values, and without notable structures. Only edges or prominent
points of buildings IoGated in the target region, such as the tower of an
airport,
2o seaport or river harbor, a harDOr entryway or a bmlding that is morntored
from the
airport or harbor regipn. have a distinctive appearance, or are reflected more
intensely, in the radat image.

Nov-02-2000 12:01 From-BERESKIPI ~ PARR CA 02322378 2000-O8 X16 T-653
P.004/013 F-734
Even a high-resolution radar image does ncrt provide a continuous image
of the target region that is comparable to a graphic, visual reproduction of
the
same region that has been dotected by the radar. Moreover, it is known that a
representation obtained by radar is only a black-and-white depiction.
EP-A-362 974 describes an arrangement in which an electro~-optical sensor
co-rotates synchronously with an antenna of a panorama radar, the antenna
being mounted to a ship- The images obtained by the radar system and the
Electro-optical sensor are superposed over one another, and the combination
images of a target region obtained in this manner are displayed continuously.
to Also in JP 8-21876, an image recorded by an optical devict~ is superposed
over a
radar image obtained by a radar system.
The significant drawback of the above-described, known systems is that
optical images that can be utilized by optical or electro-optical devices can
only
be recorded under correspondingly good visibility conditions, but not, for
example,
~s under poor visibility conditions or in fog.
OBJECT ~F THE INVENTION
It is the cabject of the invention to improve a representation obtained by a
platfom~-borne radar system in the phase of the appraaah toward a selected
Zo target region insofar that persons such as pilots, captains, navigators,
etc., who
are observing or moniEoring the target region, can identify and interpret
details
about the target region much more easily.
According to the invention, this object is accomplished with a method for
representing radar images of a target region to be monitored, the method
zs possessing the features of the chat~cterizing portion of claim 1.
Advantageous
modifications are the subject of the claims that era directly or indirectly
dependent on claim 1.
In the method of the invention, with the aid of a platform-borne data..
processing system, radar images of the selected target region that have been
2

Nov-02-2000 12:01 From-BERESKIN & PARK CA 02322378 2000-08~~16 T-653 P.005/013
F-734
generated by a platform-borne radar system, preferably a so-called forward-
looking radar or a so-called sector imaging radar, are superposed with optical
images of the same target region, the images being stored in the platform-
borne
data-processing system, in continuously-repeating time intervals, and the
combination images comprising the obtained radar images and the superposed
optical images are displayed continuously. The optical images, for example
aerial
images of the selected target region, that are to be superposed over the radar
images are stared in the data-processing system.
Optical image refers hereinafter to a continuous image of the target region
to to pe monitored that corresponds to a photographic image and is stored in
the
pfatfQrm-borne data-proGessln9 system. Continuous image refers to an image
that is generated to display only the stationary structures in the image that
are
necessary for monitoring, such as buildings and ground facilities or docks,
including the entire flying field or taxiway or the ent(re harbor.
is Llepending on the respective representation of the target region, however,
image data originating from different scanning plans can also be layered
beneath
the radar image. The above-defined optical images are particularfy well-suited
fvr
a central, perspective view, for example from an aircraft cockpit or ship's
bridge.
Aerial recordings or maps of the selected target region may also be suitable
for a
Zo plan view.
The stored, preferably also color, optical images can then be sublayered
as the background far the radar imaga$, which are adapted in their dimension's
to
the optical images, in predetermined time intervals. ~epending on the viewing
angle, the optical images may also need to be altered in terms of size and
zs viewing angle.
Upon the availability of a combination image comprising a radar iimage and
an optical image superposed over it, or an optical image layered beneath the
3

Nov-02-2000 12:01 From-BERESKIN & PARK CA 02322378 2000-08016 T-653 P.006/013
F-Z34
radar image as the t~aGkground, the persons monitoring ttte selected target
region detected by the radar, such as fixed, immobile targets, for example
puildings flr other stationary Structures or the like, cars mare easily
interpWt
paints, surfaces, edges or the like that are clearly visible in the radar
image.
In addition, with the meihpd of the invention, persons monitoring the
selected target region cannot only immediately and easily identify the
respective
points appearing in the radaf image, such as the aforementioned edges of
u~ildings, etc., with respect to their position, but they can also idsrltify
the
position precisely and reliably, thereby unambiguously associai~ng it with
Bach
l0 fixed, immobile target.
an advantageous modificatiAn of the method of the invention lies in storing
color optical images in the data-processing system, thus keeping them ready
for
retrieval. if color optical images that are subEayered as the pacicground for
the
radar images, which - as already mentioned - are adapted in their dimensions
as
stipulated py the system, and can only be displayed in black and white, this
further improves the interpretation pf the obtained combination images and an
allocation an4 identification of prominent points, such as edges, transitions,
etc.,
that are clearly distingmshed in the radar image.
According to a further advantageous embodiment of the method of the
z o invention, all of the back-scattered points of stationary elements or
targets in a
scene that are likewise present in the optical image Gan ne gated out of each
radar image preferably having an optical, continuous, color image that is
layered

Nw-02-2000 12:01 From-BERESKIN ~ PARR CA 02322378 2000-O8~o16 T-653 P.001/013
F-734
beneath it as the bacfcground- 1n the prpcess, only the back-scattered points
of
targets that are not present in the optical, image are retained in the
sublayered
optical image and dearly emphasized.
In this way, it is also possible, for example, to detect items and objects
that were not present in the generation of the optical images, and therefore
must
be presented clearly antt with emphasis to pilots, captains, navigators arid,
possibly, the persons performing the monnorWg.
In a particularly advantageous manner, combination imagES created
according to the invention can ae used not only far correctly interpreting
mobile
1 o targets, from small vehicles, transport vehicles, luggage carriers,
launches, small
ships. excursion boats and the like, up tA large vehicles, such as aircraft,
strips.
etc., but also for precisely identifying the position or region where the
moaile
objects are located.
According to an advantageous mabification of the method of the invention,
the back-scattering of Such mobile tatgets can fas emphasized in the
sublayareb,
preferapiy cc~Eor opncal image in that all back~5catterad points of stationary
elements, targets or the like in a scene are gated out of the individual radar
images.
Moreover, in accorpartce with a further embodiment of the invention, all
2 o targets, both fixs~i ana mobile, that have peen detected by the radar
system - but
are not, however, present in the optical image - can be dnplayep W such a way
that a color is allocated to the targets that remain after all stationary
targets of a
5

Nw-02-2000 12.02 From-BERESKIN & PARR CA 02322378 2000-O8~o16 T-653 P.008/013
F-734
scene have been gated out, and are not pres4nt in the opkical image. !n an
aavantageous modification of the invention, tree detected mobile targets can
be
allocated a different color from the targets appearing to be
°parfced,° and thus
s~ationary
Furthermore, -parked" and mobile targets that are not present in different
sections of the optiaa! image, but have been detected by the radar system, can
also ber displayed in different colors by sector.
According to a further advantageous modification of the methpd Qf the
invention, only oris specific section, preferably the central portion, of the
selectea
1 o target region of the radar images superposed over the optical images is
displayed with the highest-resolution mode. In contrast, the edge regions are
only displayed with a rower-resolution mode, wn~ch simplifies ant reputes the
outlay far data processWg.
If the selected target region is, far example, a runway of an airport, the
15 secnvn containing the runway, which gerterarly corresponds to the central
portion
of the selsctea target region, can be displayed with the highest-resolt~tiAn
mode
in the radar images superposed over the optical images of the runway. With
respect to me strips of lard an either side of the runway, however, a display
with
a considerably rower-resotuti4n mode is generally sufficient.
2 o To save storage and ~mp~rtational capacity, an advantageoNs
modification of the invention involves displaying the optical images at a
considerably lower rspetit~on rate than that of the images generates ay the
6

Nw-02-2000 12:02 From-BERESKIN ~ PARR CA 02322378 2000-08016 T-653 P.009/013 F-
734
platform-oorne radar system. Conseceative optical images ha~ln9 a relatively-
law
repetition rate tan also be interpolatep with respect to the respectively
previous
~ma9e.
According to the invention, the images that have been obtained and
processed by the platform-borne monitoring system are displayed at a
rEpetition
rate in the order of magnitude of about 10 to lOfJ Hz. pue to the siugsishness
of
the human eye, at a repetition rate between 50 arid 100 H2, pilots, navigators
and possibly the persons performing the monitoring patceive the display on the
monitor of the radar system as a uniform, continuous sdrias of radar images.
z o The method of the invention therefore creates numerous options for
considerably facilitating and improvirtg the intetpretation of a radar image,
Plot
only in terms of mapile objects, but objects or targets that are only present
temporarily ("parked"), and for identifying such oi~jects or targets faster,
more
accurately and more reliadly.