Note: Descriptions are shown in the official language in which they were submitted.
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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.
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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
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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
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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
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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
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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
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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.
