SURVEILLANCE METHOD FOR WIDE AREAS

Abstract: Procedure for the monitoring of large surface areas, in which procedure the area (10) to be monitored is observed by means of a monitoring unit (14) comprising a thermal camera (2) and an electromagnetic radar (3), which are rotated about a vertical shaft to scan the area to be monitored in a horizontal plane, and a processing device (13) for the processing of the data provided by the thermal camera and the radar. In the procedure, the surface area (10) to be monitored is divided into surface elements (12) as a function of the angle of rotation of the vertical shaft and the scanning distance, and monitoring criteria are defined for the surface elements; movements in the surface area to be monitored are observed by means of the electromagnetic radar (3); objects (1) differing from their surroundings in respect of temperature are searched by means of the thermal camera (2); and the location of the object, i.e. the surface element corresponding to the object, is determined and the object is identified by means of either the radar or the thermal camera, depending on the conditions and the distance of observation.

Description: SURVEILLANCE METHOD FOR WIDE AREAS The present invention relates to a procedure for monitoring large surface areas, which has been de¬ veloped especially for the monitoring of outdoor areas to detect the presence of people, but which can just as well be used in large indoor spaces and for other types of area supervision. The procedure of the invention can be applied to the supervision of various storage areas, supervi- sion of working sites, frontier supervision, passage control in industrial areas, supervision of military areas, airports, etc. In the various applications mentioned above and in corresponding applications where supervision is needed, the monitoring equipment mainly consists of video cameras and various optical, mechanical or elec¬ trical switches, sensors or alarm systems designed to detect movements or other effects produced by an ob¬ ject moving in the area watched over. However, prior-art solutions have significant drawbacks. Weather and illumination conditions render the video camera inapplicable for effective monitoring of outdoor areas. The various switches, sensors and alarm devices used serve relatively local needs and are therefore required in large quantities when a large area is to be monitored. Thus, building and es¬ pecially maintaining a monitoring system is expensive. Moreover, different individual alarm switches are of¬ ten relatively easy to evade or to make inoperative. The object of the present invention is to eliminate the above-mentioned drawbacks. A specific object of the invention is to produce a new procedure which allows a maximal land and/or water area to be monitored and supervised in a simple and centralized manner from a single observation point. As for the features characteristic of the in¬ vention, reference is made to the claims. In the procedure of the invention for the monitoring of large surface areas, the area to be su- pevised is monitored substantially by means of a moni¬ toring unit located at one point and comprising both a thermal camera and an electromagnetic radar, which are rotated about a vertical axis to scan the area in a horizontal plane. Moreover, the monitoring unit com¬ prises a suitable processing device for the processing of the data supplied by the thermal camera and radar and for performing the functions required by the data obtained, such as issuing an alarm. According to the invention, the area to be monitored is divided into surface elements as a function of the angle of rota¬ tion of the vertical shaft and the scanning distance, and monitoring criteria are defined for each surface element. These actions are performed in the memory and files of the processing device. The monitoring crite¬ ria may be the same for the entire area to be moni¬ tored, in which case they need not be defined sepa- rately for different surface elements. The criteria may also be different for each surface element or for larger groups of surface elements. In the procedure of the invention, movements in the surface area to be monitored are observed by means of an electromagnetic radar and, by means of a thermal camera, objects dif¬ fering from their surroundings in respect of tempera¬ ture are searched and discriminated. In addition, de¬ pending on the circumstances and the distance of ob¬ servation, either the radar or the thermal camera is used to define the location of the object, i.e. the surface element within which the object has been de¬ tected, and to identify the object detected. The thermal camera and the radar are prefera¬ bly rotated about a vertical shaft simultaneously, or the thermal camera and the radar are connected to¬ gether so that they will scan the same sector of the area at the same time. Thus, the information obtained from each can be immediately compared with that ob¬ tained from the other device and, if necessary, an alarm can be issued immediately. It is also possible to turn the thermal cam- era and the radar about the vertical shaft independ¬ ently of each other, in which case both can be used continuously or the scanning is performed by only one of the devices and only if the information obtained contains something suspicious, the area in question is checked by the other device as well. In the procedure of the invention, the entire area to be monitored, which may be a circle or a large sector of a circle, such as a semicircle, is prefera¬ bly divided into sectors opening from the monitoring unit in all directions over the surface area to be monitored, and these sectors are additionally divided into surface elements in the direction of the scanning distance. In the procedure of the invention, in addi- tion to horizontal rotational scanning, the radar preferably scans in the direction of distance with the selected surface element resolution. In this case, the echo from each surface element is subjected to an FFT transformation, thus distinguishing moving objects from stationary ones and determinining the velocity and distance of a moving object. Different parts of the area to be monitored may have different supervision criteria, e.g. such that for some parts an alarm is issued upon any move- ment, in other parts movement is always allowed and in yet other parts movement is only allowed at certain times. In this way, surface elements having the same supervision criteria can be combined into a surface element group which is treated as a coherent whole in regard of alarms. In the procedure of the invention, an object in the area to be monitored can be detected on the ba- sis of its movement by means of the radar and on the basis of a temperature deviating from the surroundings by means of the thermal camera. After the object has been detected in one of these ways, the sector in which the object is located, i.e. the sector just ob¬ served will also be known automatically. Thus, the ex¬ act location of the object can be established on the basis of the sector and the distance data given by the radar. It is also possible to determine the surface element corresponding to the object by means of the thermal camera on the basis of the observation angle. In an embodiment of the invention, when the location of an object, i.e. its direction and distance from the point of observation, is known, the size and shape of the object can be established by means of a thermal camera and this information can be processed by a suitable image processing technique to identify the object itself, i.e. e.g. whether the object is a human being, a group of people or a larger or a smaller animal. In this way, for instance small ani¬ mals, such as hares and foxes, can be removed from the alarm list and an alarm is only issued upon detection of people and large animals, such as elks and bears. As even the best thermal cameras only have a resolution that is sufficient for identifying an ob¬ ject at a distance of max. 500 m in favourable condi¬ tions, an embodiment of the invention uses the radar for object identification, in which case the system has been taught what the radar measurement response e.g. for a human being should be at different dis¬ tances, i.e. what the radar cross-section of possible different objects is like. Thus, the detected object can be identified from the radar signal response on the basis of the distance data. The identification process can additionally be assisted by using the ob¬ ject velocity obtained by radar. Radar equipment can also be used for object identification at shorter dis- tances in bad conditions, e.g. in rainy weather. In this case, the thermal camera is only used to distin¬ guish warm living objects from other objects. The radar used in the procedure of the inven- tion generally works in the same way in all weather conditions, whereas the thermal camera is signifi¬ cantly affected by the weather. For this reason, the procedure of the invention preferably comprises the measurement of temperature both in shade and in a shadefree place in the area to be monitored and also the measurement of the amount of thermal radiation from the sun in a shadefree place e.g. by means of a solar cell, and the information thus obtained can be used to control the equipment. Similarly, atmospheric humidity can be measured to detect possible rainy con¬ ditions and to adjust the thermal camera. These meas¬ ured data are preferably also utilized in making the decision as to whether the radar or the thermal camera is to be used for object identification. In addition, the procedure of the invention may also include the measurement of wind direction and force to provide information that enables the system to recognize various movements detected by the radar that should not lead to an alarm. Such movements may include e.g. the sway of trees and plants in general and the movements of boats anchored at a quay. The procedure of the invention has signifi¬ cant advantages as compared with prior art. The proce¬ dure of the invention does not require any sensor or alarm system built over the entire area to be moni¬ tored, but instead a single apparatus erected in a suitable place is sufficient. The procedure of the in¬ vention allows selective supervision of the entire area to be monitored, in other words, as the objects detected can be identified and their exact location is known, alarms can be issued only about desired objects in desired areas at desired times. Moreover, the pro- cedure of the invention allows very large areas to be supervised as a unity, because with modern technology and radar equipment and thermal cameras available, the procedure can be applied to monitor areas exceeding 1000 m in radius, which means that the entire surface area to be monitored may be over 3 km 2 . In addition, the area to be monitored can be divided into sectors with an angle e.g. below one degree and the sectors can be further divided in the radial direction into surface elements at 30-m intervals, which means that the location of an object can be accurately determined even at the extreme limits of the area to be moni¬ tored. In the following, the invention is described in detail by referring to the attached drawings, in which Fig. 1 is a diagram representing the equip¬ ment used in the procedure of the invention, and Fig. 2 illustrates the use of the equipment in Fig. 1 for the monitoring of a surface area. The equipment shown in Fig. 1 comprises a monitoring unit 14 placed on top of a column or other suitable structure or building of sufficient height. The monitoring unit comprises a thermal camera 2 and an electromagnetic radar 3. By means of a servo-system 4, these can turned horizontally and, if necessary, vertically as well. The radar and the thermal camera together with the servo-system are connected via a ca¬ ble 6 to a processing device 13 for the control of the whole monitoring system and the processing of the data obtained. In the embodiment illustrated by Fig. 1, the thermal camera 2 and the radar 3 are so directed that the beam 9 of the thermal camera and the radar beam 8 are directed in the same direction, i.e. they scan the same area simultaneously. Moreover, connected to the processing device 13 is a solar cell 20, a thermometer 21 in a shadefree place, a thermometer 22 in a shady place, a hygrometer 23 and a wind gauge 24, which make it possible to take the weather conditions prevailing in the area 10 to be monitored and their effects on the operation of the radar and thermal camera into account. The procedure of the invention is used in ac¬ cordance with Fig. 2 e.g. as follows. The radius of a circular area to be monitored may be over 1000 m. At the centre of the area there is a monitoring unit 14, which comprises both a thermal camera 2 and an elec¬ tromagnetic radar 3, mounted on a structure 5 of suf¬ ficient height. The entire area to be monitored has been divided into sectors 11, the sector width corre¬ sponding to the widths of the beams 9 and 8 of the thermal camera 2 and radar 3. The magnitude of the sector angle is preferably 0.5 - 1°. The radar used may be any radar device based on electromagnetic radiation having a range sufficient for the area in question. As compared with ultrasonic or laser beam radar equipment, a radar based on elec¬ tromagnetic radiation has the advantage of being con¬ siderably less sensitive e.g. to rain and fog. As to its operating principle, the radar may be either a doppler radar device, in which case it detects move- ments occurring within the beam, or it may be based on normal distance measurement, in which case the radar measures the distance to the objects within the beam, or a combination of these. The area under the radar beam, i.e. the sec- tor 11, is divided longitudinally into surface ele¬ ments 12 of a suitable size, so the radar scans the area under the beam in the direction of distance. If the radar used only reacts to moving objects, it will not produce any disturbing ground return. Each echo returned from a surface element is subjected to an FFT transformation. In this way, only moving objects can be picked out and the velocity of these objects can be determined. As the surface element being observed is thus known, the distance, i.e. the location of the ob¬ ject can also be determined. In this way, an object moving in the area to be monitored can be detected and located. After an object has been detected by the ra¬ dar and its location or the corresponding surface ele¬ ment is known, the thermal camera can be used to exam¬ ine the shape of the thermal image radiated by the ob- ject, if the conditions are good enough and the dis¬ tance is not too long. As the exact distance of the object is known, the size of the object can also be determined from the image detected by the thermal cam¬ era. After the size and shape of the object have been perceived by the thermal camera, the object can be sufficiently identified by the image processing system of the processing unit 13 to provide information as to whether an alarm or other measures are necessary. Es¬ pecially in frontier supervision, image processing and the ability to distinguish large warm animals such as elks, reindeer, bears and wolves from human beings renders the procedure extremely functional and usable. If the distance of an object as measured us¬ ing the best technology available at present is e.g. over 500 metres, and even at shorter distances in rainy or foggy weather, identifying an object by means of a thermal camera is impossible. Therefore, this system has been taught to recognize objects from the radar response as well. In other words, the system knows what sort of a radar response is produced by a human being or a corresponding object at different distances from the radar, so the radar can also be used for object identification. Thus, the basic principle of the apparatus and procedure of the invention is to use both a radar device 3 and a thermal camera 2 to scan the area to be monitored. The radar is used to detect movements in the area to be monitored. The image provided by the thermal camera is continuously examined to detect spots that differ in temperature from the surrounding area. When either a movement or a temperature change is detected, this will cause closer examination of the situation. An eventual alarm is issued after the ob¬ ject has been examined more closely by radar or ther¬ mal camera, depending on the conditions and observa¬ tion distance, and after the object has been located and identified as accurately as possible and if the supervision criteria for the area of observation re¬ quire an alarm. It is also possible to perform several monitoring scanning cycles before activating an alarm. In this way, the presence of a suspicious object can be verified and the amount of false alarms reduced. The thermal camera can also be turned in a desired di¬ rection to follow an object or to verify a radar ob¬ servation. Another way to use the procedure of the in- vention in surveillance is by only registering all in¬ formation obtained, without giving any alarms. Thus, for instance the supervision of an area to be closely monitored and the prevention of intrusions can be achieved by placing a monitoring unit as provided by the invention at the border of the area under surveil¬ lance, so that the apparatus will monitor the area in a semi-circular surveillance sector and give an alarm when necessary while the other semicircular sector monitors and registers actions occurring in the neigh- bourhood. This makes it possible to register abnormal actions even in the vicinity of the area under sur¬ veillance, thus significantly contributing towards preventing illicit activities in the area under sur¬ veillance.

Claims: CLAIMS 1. Procedure for the monitoring of large sur¬ face areas, in which procedure the area (10) to be monitored is observed by means of a monitoring unit (14) comprising a thermal camera (2) and an electro¬ magnetic radar (3) , which are rotated about a vertical shaft to scan the area to be monitored in a horizontal plane, and a processing device (13) for the processing of the data provided by the thermal camera and the ra- dar, c h a r a c t e r i z ed in that - the surface area (10) to be monitored is divided into surface elements (12) as a function of the angle of rotation of the vertical shaft and the scanning distance, and monitoring criteria are defined for the surface elements, - movements in the surface area to be moni¬ tored are observed by means of the electromagnetic ra¬ dar (3), - objects (1) differing from their surround- ings in respect of temperature are searched by means of the thermal camera (2), - the location of the object, i.e. the sur¬ face element corresponding to the object, is deter¬ mined and the object is identified by means of either the radar or the thermal camera, depending on the con¬ ditions and the distance of observation. 2. Procedure as defined in claim 1, c h a r ¬ a c t e r i z e d in that the thermal camera (2) and the radar (3) are turned about the vertical shaft simulta- neously, scanning the same area. 3. Procedure as defined in claim 1, c h a r ¬ a c t e r i z e d in that the thermal camera (2) and the radar (3) are turned about the vertical shaft inde¬ pendently of each other. 4. Procedure as defined in claim 1, c ha r ¬ a ct e r i z e d in that the area (10) to be monitored is divided into sectors (11) opening from the monitor- ing unit (14) in all directions and these sectors are divided into surface elements (12) in the direction of the scanning distance. 5. Procedure as defined in claim 4, c ha r - act e r i z e d in that, in addition to horizontal ro¬ tational scanning, the radar (3) is also used to scan in the direction of distance with a selected surface element resolution and that the echo from each surface element is subjected to an FFT transformation, thus distinguishing moving objects from stationary ones and determinining their distance, i.e. the surface element concerned, and their velocity. 6. Procedure as defined in any one of claims 1 - 5, ch a r a c t e r i z ed in that surface elements having the same supervision criteria are combined into a surface element group. 7. Procedure as defined in claim 1, ch a r ¬ a c t e r i z e d in that an object (1) is detected by radar (3) on the basis of movement. 8. Procedure as defined in claim 1, c h a r ¬ a ct e r i z e d in that an object (1) is detected by thermal camera (2) on the basis of temperature differ¬ ence. 9. Procedure as defined in claim 1, cha r - a c t e r i z e d in that the location of the object is determined on the basis of a known direction of obser¬ vation, such as the sector being monitored, and the distance data given by the radar. 10. Procedure as defined in claim 1, ch a r - a c t e r i z e d in that the location of the object is determined by thermal camera on the basis of the angle of observation of the object. 11. Procedure as defined in claim 1, c h a r ¬ a ct e r i z e d in that the object is identified on the basis of a known distance and the size and shape of the object as obtained by the thermal camera. 12. Procedure as defined in claim 1, c a - a c t e r i z e d in that the object is identified on the basis of a known distance and the radar measure¬ ment response or the radar cross-section of the ob¬ ject. 13. Procedure as defined in claim 12, c h a r a c t e r i z e d in that the velocity of the ob¬ ject is used as auxiliary data in object identifica¬ tion. 14. Procedure as defined in any one of claims 1-13, c ha r a c t e r i z ed in that, to adapt the op¬ eration of the equipment to the prevailing conditions, the procedure comprises the measurement of temperature in shade and in a shadefree place and the measurement of the amount of thermal radiation from the sun in a shadefree place. 15. Procedure as defined in any one of claims 1-13, c ha r a c t e r i z ed in that, to adapt the op¬ eration of the equipment to the prevailing conditions, the procedure comprises the measurement of atmospheric humidity. 16. Procedure as defined in any one of claims 1-13, c ha r a c t e r i z e d in that the direction and force of the wind are measured to distinguish move¬ ments caused by the wind as detected by the radar from other movements in the area being monitored.

Inventors: KORJA JARI, RAUTANEN JOUKO, KORJA, JARI, RAUTANEN, JOUKO
Applicants: KORJA JARI, RAUTANEN JOUKO, KORJA, JARI, RAUTANEN, JOUKO
Application year: 1997
Main classification: G01S13
IPC codes: G01S13