GB2060308A - Method of tracking a target - Google Patents
Method of tracking a target Download PDFInfo
- Publication number
- GB2060308A GB2060308A GB8030214A GB8030214A GB2060308A GB 2060308 A GB2060308 A GB 2060308A GB 8030214 A GB8030214 A GB 8030214A GB 8030214 A GB8030214 A GB 8030214A GB 2060308 A GB2060308 A GB 2060308A
- Authority
- GB
- United Kingdom
- Prior art keywords
- target
- image
- sensor
- stored
- identified
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S3/00—Direction-finders for determining the direction from which infrasonic, sonic, ultrasonic, or electromagnetic waves, or particle emission, not having a directional significance, are being received
- G01S3/78—Direction-finders for determining the direction from which infrasonic, sonic, ultrasonic, or electromagnetic waves, or particle emission, not having a directional significance, are being received using electromagnetic waves other than radio waves
- G01S3/782—Systems for determining direction or deviation from predetermined direction
- G01S3/785—Systems for determining direction or deviation from predetermined direction using adjustment of orientation of directivity characteristics of a detector or detector system to give a desired condition of signal derived from that detector or detector system
- G01S3/786—Systems for determining direction or deviation from predetermined direction using adjustment of orientation of directivity characteristics of a detector or detector system to give a desired condition of signal derived from that detector or detector system the desired condition being maintained automatically
- G01S3/7864—T.V. type tracking systems
- G01S3/7865—T.V. type tracking systems using correlation of the live video image with a stored image
Abstract
A method of tracking a target, especially military aircraft, passers-by or the like, of the type in which an image-generating sensor is caused to follow a target by a servo-system, is characterised in that predetermined characteristics of expected targets are stored, the sensor image is correlated with the stored target characteristics until a similarity threshold is exceeded, and the actual image of the target as identified by the correlation tracker is then stored and used to control the follow-up servo-system.
Description
SPECIFICATION
Method of tracking a target
The present invention relates to a method of tracking a target, especially military aircraft, passers-by and the like.
Tracking systems are known which comprise an image-generating sensor, a servo-system for following the sensor and a correlation tracker, preferably a cross-correlation tracker.
In German (Fed. Rep.) patent specification No.
P 28 42 684.8 there is proposed a device for recognizing and tracking a target, the device consisting of an optronic image sensor, an image evaluation logic, an automatic follower system for the image sensor and operating apparatus. The image evaluation logic operates on the correlation principle by comparing temporarily stored images of the current scene with a stored reference view of the target and supplies according to each image a filing signal to the automatic follower.This tracker device is suitable for a wide variety of tracking situations with ground targets in front of highly structured backgrounds and ensures optimum co-operation between the operator and the device by the fact that an electronic decision or learning logic provides for the actualization or selection of various target stores, which are connected to a common data bus, through information such as similarity between stored and actual target view, target speed, target masking etc. Moreover, devices are provided which make possible the inclusion of information of importance to the operator in the monitor of the apparatus.
According to the present invention there is provided a method of tracking a target by means of a tracking system comprising an imageproducing sensor, a servo system to enable sensor follow-up of a target, and a correlation tracker, the method comprising the steps of storing predetermined characteristics of a target in the correlation tracker, correlating an image produced by the sensor with the stored target characteristics until a threshold of similarity between the image and target characteristics is exceeded thereby to identify the presence of an image of the target in the sensor image, and storing the identified target image in the correlation tracker.
Said predetermined characteristics may comprise views of the target or a plurality of different shapes of the target.
Expediently, the method comprises the further step, after the step of storing the identified target image, of initiating automatic derivation and storage of instantaneous reference data concerning the target during tracking thereof by the sensor.
In one example, the method may comprise the further step, after said correlating step, of automatically correlating the image produced by the sensor with the stored target characteristics or stored identified target image until the threshold of similarity is again exceeded thereby to identify the presence of an image of another such target in the sensor image.
Expediently, the distance of the sensor from the targets providing the identified target images is calculated by reference to the distance between the target images.
In another example, the method may comprise the further step of assigning a marker to the identified target image in the sensor image. Such a marker may comprise a frame framing the target image.
Expediently, the method comprises the further steps of controlling the sensor to coarsely capture the target in the sensor image and automatically centering the sensor on the target by reference to the difference between successive target images obtained by correlating the sensor image with said predetermined target characteristics and subsequently with the coarsely captured target image.
The method may further comprise the preliminary step of determining the target characteristics to be stored by scanning a section of the sensor image to select a target image therein having predetermined minimum characteristics with respect to degree of contrast and distinctiveness of form. The step of determining may additionally comprise calculating reference values from the image sensor and a target characteristics store for use as a maximum correlation function for target image contrast and form.
Expediently, the method also comprises the steps of tracking movement of the selected target image in the sensor image and, on the target image reaching an edge of the sensor image, repeating said determining step by scanning said section of the sensor image to select a further such target image therein.
The method may comprise the further step of continuously varying the size of the sensor image by means of a zoom lens to correlate the size of the identified target image with stored target characteristics relating to size. Alternatively, when said predetermined characteristics comprise at least one view of the target, the size of the stored target view may be continuously varied by means of an electronic magnification lens to correlate the size of the stored target view with that of the identified target image. If, however, said predetermined characteristics comprise a view of the target in a plurality of different sizes, the size of the identified target image can be correlated with a correspondingly sized stored view of the target.
In yet another example of the method, where size correlation is involved, the method may comprise the further steps of calculating the distance of the sensor from the target as a function of the correlation of the size of the identified target image with the stored target size characteristic, and superimposing, on an observation image produced by an associated wide field observation camera, reference means identifying target position in the observation image and target range based on the distance measurement. The observation camera can then be controlled in dependence on the reference means to automatically centre on the identified target position, and/or can be controlled to provide a magnified image of the region comprising the identified target position.
A method exemplifying the present invention makes possible an automatic target recognition, with the additional possibilities of automatic target marking and an automatic searching for further targets after a search and/or tracking operation of a first target has been carried out.
The invention will now be discussed in more detail with reference to the following Examples: 1. Target tracking in the surveillance of important equipment for protection of the equipment, for example, against sabotage, wherein, for example, a passer-by may be automatically recognized and subsequently automatically tracked; 2. Target tracking in the case of threat from several like targets, for example, flights of military aircraft; 3. Target tracking in quantitative detection of an aircraft flight path; and 4. Target tracking in surveiliance of two interesting regions in the field of view of a thermal image camera or television camera.
In Example 1, a target tracking system operating by a method exemplifying the invention is used as an object protection installation. At the commissioning of such an object protection installation, properties of a passer-by serving as target, such as for example the image of the passer-by or the typical upper body of a human being, can be stored by means of a PROM in the target memory of a correlation tracker. It is also possible, by reading off from tapes, to write into the target memory a quite specific image of a person. If the correlation tracker is then brought into the waiting state, i.e. the correlation tracker and object protection installation are brought into operation, then by means of a maximum monitoring the correlation function is observed to see whether a structure possessing sufficient agreement with the stored image appears in the instantaneous sensor image.If this is the case, the correlation tracker automatically converts to storing the actual (current) image of the target in the target memory of the correlation tracker. After this image has been stored in the target memory, an automatic learning target tracking operation can then be initiated. This will advantageously be the case in the majority of monitoring installations.
With an object protection installation of this type, it is also possible, after the recognition and assignment of a current image of a first target, to search for further target images and track them.
A target tracking system exemplifying the method of this invention can be used particularly advantageously to detect, in accordance with
Example 2, a threat from a number of military aircraft. In this case, the correlation tracker is so extended by redundant design with multiple search window logic and a plurality of target
memories or by a multiple equipping of identical
individual trackers, that the target tracking system subsequent to the capturing and fixing onto a target, for example a military aircraft, can capture,
mark and track further targets independently of the first tracker operation.Since it can be assumed, for flights of military aircraft, that all the targets appear the same at approximately the same distance, it is also possible, after one target has been recognized, to automatically search for, capture and track further targets possessing the original view of the first target, by means of the obtained properties of the target or by means of the obtained target view, a so-called anticipation image.
In this connection, it is especially advantageous that the method exemplifying the present invention makes it possible to automatically centre a manually coarsely captured target by correlation with the predetermined properties of the target, preferably a view of the target, and subsequent correlation with the manually coarsely captured target image. In the switched-in image of the target and in the anticipation image of the target, the correlation tracker finds the target object in the sensor image, the calculated target filings being distinguished by a filing difference vector in theX-direction and Y-direction. By subtraction of the filings successively established by the two target images, the filing difference vector can be calculated and utilized for automatic centering.The automatic centering renders unnecessary a time-consuming, accurate fixing onto the target by the operator. It is sufficient to coarsely assign a target to the target tracking system, for example, by manual operation or by radar assignment. The correlation tracker then searches for the target in a larger search area with the assistance of the predetermined characteristics of the target or by means of a target view - that is the anticipation image and accepts the target into the target memory when an agreement threshold is exceeded.
In Example 3, which relates to a quantitative determination of flight paths of flying objects, provision is made to house a target tracking system operating according to the said Example, together with a television camera constituting the image-generating sensor, on board an aircraft. It is then possible to automatically fix the correlation tracker on ground structures at the upper edge of the image and to record the passage of a marking window through the image or to utilize it for controlling image processing operation. Whenever the tracked ground structure strikes the lower or a side edge of the image, the correlation tracker can automatically guide the marking window back to the upper image edge or capture, store and track another ground structure situated at the upper image edge.
In this connection there is the problem that structures which can be tracked by means of pattern recognition, i.e. which possess a certain contrast and do not consist, for example as does the horizon, only of an edge that is difficult to follow, must be stored in the target memory. To solve this problem it is provided that, before the final input and storage of the ground structure into the target memory of the correlation tracker, the upper region of the image is searched with the assistance of the correlation tracker and a search strategy.The correlation tracker does not go over into normal operation, i.e. does not hold a specific structure and store it in its target memory, until a contrast value that can be obtained from the target memory with the assistance of the correlation tracker has reached a specific minimum value and the maximum of the correlation function is sufficiently high and is sufficiently limited horizontally and vertically. By the measured values ascertained in this manner for contrast and form of the maximum of the correlation function, storage data for the targets, the properties and target views of which are unknown, can thus be ascertained.
In Example 4, the target tracking system is employed for use in distance measurement between two targets and the image sensor. For this purpose, two windows and two target memories are available to the correlation tracker.
When the tracker is switched onto two target structures, a structure is assigned to each window and the distance between the two windows and thus the target structure is monitored. As an example of a distance measurement, the measurement of the distance between a ship equipped with a target tracking system and a drilling rig may be considered. On the drilling rig, two high-contrast marking points are mounted at a predetermined distance apart and, as the ship approaches the drilling rig. are tracked by the correlation tracker. As the ship approaches the drilling rig, the operation becomes simplified, as only one marking point has to be assigned to the correlation tracker and the correlation tracker itself automatically searches, recognizes and tracks the second marking point, as in Example 2.
By a method exemplifying the invention, a problem is also solved which occurs particularly in
Example 1, i.e. the monitoring of important equipment. In the recognizing of a person by an object protection installation in the aforedescribed manner, a problem lies in the unknown distance and thus in the size of the person in the sensor image. Before the correlation is carried out, either the size of the sensor image or the view of the person in the target memory must be changed in such a way that a similarity can be established between the two images. Examples of three possible solutions are: 1. In front of the image sensor, for example in front of a television camera, a zoom lens is disposed which continuously varies the sensor image in its size for rapid and reliable recognition of the target.
2. The image in the target memory of the correlation tracker is continuously varied in its size by means of an electronic magnifying lens, in that this image is read out with varying degrees of coarseness.
3. Differently sized views of a target are input into
and stored in the target memory of the correlation
tracker and are made available for carrying out a
correlation operation.
In these three examples, there is also the
possibility of being able to derive the distance
information from the recognized target size. In an
observation monitor, a mark at the location of a
target object can be recorded on the overall view
of the object to be protected and thus, in spite of the large field of view of a television camera, the
target object can be made visible. An automatic swinging of the camera onto the marked position
of the target object is possible, as also is a change
of focal length of the field lens and thus an
enlarged representation of the object.
Claims (20)
1. A method of tracking a target by means of a tracking system comprising an image-producing sensor, a servo system to enable sensor follow-up of a target, and a correlation tracker, the method comprising the steps of storing predetermined characteristics of a target in the correlation tracker, correlating an image produced by the sensor with the stored target characteristics until a threshold of similarity between the image and target characteristics is exceeded thereby to identify the presence of an image of the target in the sensor image, and storing the identified target image in the correlation tracker.
2. A method as claimed in claim 1 , wherein said predetermined characteristics comprise views of the target.
3. A method as claimed in either claim 1 or claim 2, comprising the further step, after the step of storing the identified target image, of initiating automatic derivation and storage of instantaneous reference data concerning the target during tracking thereof by the sensor.
4. A method as claimed in any one of the preceding claims, comprising the further step, after said correlating step, of automatically correlating the image produced by the sensor with the stored target characteristics until the threshold of similarity is again exceeded thereby to identify the presence of an image of another such target in the sensor image.
5. A method as claimed in any one of claims 1 to 3, comprising the further step after said correlating step of automatically correlating the image produced by the sensor with the stored identified target image until the threshold of similarity is again exceeded thereby to identify the presence of an iamge of another such target in the sensor image.
6. A method as claimed in any one of the preceding claims, comprising the further step of applying a marker to the identified target image in the sensor image.
7. A method as claimed in claim 6, wherein the marker comprises a frame framing the target image.
8. A method as claimed in any one of the preceding claims, comprising the further steps of controlling the sensor to coarsely capture the target in the sensor image and automatically centering the sensor on the target by reference to the difference between successive target images obtained by correlating the sensor image with said predetermined target characteristics and subsequently with the coarsely captured target image.
9. A method as claimed in claim 1, comprising the preliminary step of determining the target characteristics to be stored by scanning a section of the sensor image to select a target image therein having predetermined minimum characteristics with respect to degree of contrast and distinctiveness of form.
10. A method as claimed in claim 9, wherein the step of determining further comprises calculating reference values from the image sensor and a target characteristics store for use as a maximum correlation function for target image contrast and form.
11. A method as claimed in either claim 9 or claim 10, comprising the steps of tracking movement of the selected target image in the sensor image and, on the target image reaching an edge of the sensor image, repeating said determining step by scanning said section of the sensor image to select a further such target image therein.
12. A method as claimed in either claim 4 or claim 5, comprising the further step of calculating the distance of the sensor from the targets providing the identified target images by reference to the distance between the target images.
13. A method as claimed in claim 1, comprising the further step of continuously varying the size of the sensor image by means of a zoom lens to correlate the size of the identified target image with stored target characteristics relating to size.
14. A method as claimed in claim 1, wherein said predetermined characteristics comprise at least one view of the target and the method comprises the further step of continuously varying the size of the stored target view by means of an electronic magnification lens to correlate the size of the stored target view with that of the identified target image.
1 5. A method as claimed in claim 1 , wherein said predetermined characteristics comprise a view of the target in a plurality of different sizes and the method comprises the further step of correlating the size of the identified target image with a correspondingly sized stored view of the target.
16. A method as claimed in any one of the preceding claims, wherein said predetermined characteristics comprise a plurality of different shapes of the target.
17. A method as claimed in any one of claims 13 to 1 5, comprising the further steps of calculating the distance of the sensor from the target as a function of the correlation of the size of the identified target image with the stored target size characteristics, and superimposing, on an observation image produced by an associated wide field observation camera, reference means identifying target position in the observation image and target range based on the distance measurement.
18. A method as claimed in claim 17, comprising the further step of controlling the observation camera in dependence on the reference means to automatically centre on the identified target position.
19. A method as claimed in claim 17 or 18, comprising the further step of controlling the observation camera to provide a magnified image of the region comprising the identified target position.
20. A method of tracking a target by means of a tracking system, the method being substantially as hereinbefore described with reference to any one
Examples 1 to 4.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19792939656 DE2939656C2 (en) | 1979-09-29 | 1979-09-29 | Method of pursuing goals |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB2060308A true GB2060308A (en) | 1981-04-29 |
| GB2060308B GB2060308B (en) | 1983-08-03 |
Family
ID=6082316
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8030214A Expired GB2060308B (en) | 1979-09-29 | 1980-09-18 | Method of tracking a target |
Country Status (3)
| Country | Link |
|---|---|
| DE (1) | DE2939656C2 (en) |
| FR (1) | FR2467410A1 (en) |
| GB (1) | GB2060308B (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0139292A2 (en) * | 1983-10-17 | 1985-05-02 | Hitachi, Ltd. | Navigation apparatus for mobile system |
| EP0190742A2 (en) * | 1985-02-08 | 1986-08-13 | Hitachi, Ltd. | Guidance system for a mobile robot |
| EP0528077A1 (en) * | 1991-08-20 | 1993-02-24 | Selbourne Limited | Airborne radar system with a camera for tracking low flying objects |
| CN111723616A (en) * | 2019-03-20 | 2020-09-29 | 杭州海康威视系统技术有限公司 | Method and device for measuring personnel relevance |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3241896A1 (en) * | 1982-11-12 | 1984-05-17 | Licentia Patent-Verwaltungs-Gmbh, 6000 Frankfurt | Method for improving the image processing in optronic missile detection devices |
| DE3415685A1 (en) * | 1984-04-27 | 1985-11-07 | Licentia Patent-Verwaltungs-Gmbh, 6000 Frankfurt | METHOD FOR DETECTING SCENE CHANGES IN FILMS AND VIDEO RECORDINGS AND FOR MONITORING OBJECTS BY VIDEO CAMERAS |
| CN107463108B (en) * | 2017-04-20 | 2020-03-24 | 中国科学院国家天文台 | Simulation system and method of space telescope related tracker |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| SE351302B (en) * | 1970-02-11 | 1972-11-20 | S Ahlbom | |
| GB1568058A (en) * | 1975-11-21 | 1980-05-21 | Emi Ltd | Tracking and/or huidance systems |
| SE411400B (en) * | 1977-11-02 | 1979-12-17 | Saab Scania Ab | FOR FOLLOWING AN OBJECT INTENDED CORRELATION FOLLOWER |
| DE2842684C2 (en) * | 1978-09-30 | 1982-12-30 | Licentia Patent-Verwaltungs-Gmbh, 6000 Frankfurt | Device for recognizing and tracking a target |
-
1979
- 1979-09-29 DE DE19792939656 patent/DE2939656C2/en not_active Expired
-
1980
- 1980-09-18 GB GB8030214A patent/GB2060308B/en not_active Expired
- 1980-09-25 FR FR8020605A patent/FR2467410A1/en not_active Withdrawn
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0139292A2 (en) * | 1983-10-17 | 1985-05-02 | Hitachi, Ltd. | Navigation apparatus for mobile system |
| EP0139292B1 (en) * | 1983-10-17 | 1991-01-23 | Hitachi, Ltd. | Navigation apparatus for mobile system |
| EP0190742A2 (en) * | 1985-02-08 | 1986-08-13 | Hitachi, Ltd. | Guidance system for a mobile robot |
| EP0190742A3 (en) * | 1985-02-08 | 1987-10-28 | Hitachi, Ltd. | Method for guiding a mobile object and guidance system |
| EP0528077A1 (en) * | 1991-08-20 | 1993-02-24 | Selbourne Limited | Airborne radar system with a camera for tracking low flying objects |
| CN111723616A (en) * | 2019-03-20 | 2020-09-29 | 杭州海康威视系统技术有限公司 | Method and device for measuring personnel relevance |
| CN111723616B (en) * | 2019-03-20 | 2023-06-02 | 杭州海康威视系统技术有限公司 | Personnel correlation measurement method and device |
Also Published As
| Publication number | Publication date |
|---|---|
| DE2939656A1 (en) | 1981-04-02 |
| FR2467410A1 (en) | 1981-04-17 |
| DE2939656C2 (en) | 1983-03-10 |
| GB2060308B (en) | 1983-08-03 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |