Thermal imaging systems are most commonly associated with the detection of heat leakage from buildings, inspection of defects on technical installations or building protection against the unwanted entry of undesirable persons. Interestingly, these thermo-vision systems have been recently and rapidly used in agriculture and game management as well. The purpose of this usage lies mainly in the effort to locate and count game. And it does not concern just the purpose of game hunting. On the contrary, the thermal systems address a commonly debated issue, e.g. the protection of baby animals in the fields during harvest and a control of the number of pieces of rare game in game preserves.
Introduction to the issue
Every year thousands of deer fawns, in particular, die under mowers and combine harvesters. A deer typically represents the group of game that hides their young from predators on cultivated pastures of agricultural land for the first two months. Up to 96% of the young are born in the period from May to June, and therefore remain lying in the fields until the harvest time, which comes in July and August. Due to their natural instincts, the young remain clung to the ground in the event of imminent danger and thus make it harder for farmers driving agricultural machinery to detect them. Unfortunately, up to 25% of fawns are killed in this way. What is more, their deaths are not the only problem that is connected to this disaster. In case the dead animal bodies are inadvertently brought into the silage, dangerous botulinum toxin is produced by proliferating bacteria, which causes serious health risks for farmed animals that are fed on the silage. Thus, further losses occur in addition to the death of the game.
Since the beginning of agricultural industrialisation, gamekeepers and farmers have been trying to address and tackle this issue. There have been plenty of methods used and tested for detecting the baby animals. Regrettably, neither the visual inspection of the fields by gamekeepers followed by transferring the found fawns to safety, nor the acoustic jammers have the desired result. Firstly, it is very difficult to find the animal which lies so close to the ground. Secondly, its coat colour provides great camouflage since it is so identical to the ripening grain, making the animal hard to see in the field. Moreover, fawns tend to return to the field after being carried away; some of them were found even in the close vicinity of scarring devices.
Animal camouflage works only in the visible spectrum of radiation. Infrared radiation, i.e. heat, which the young emit, can give them away even in grain fields. Because the skin and subcutaneous tissue of a fawn is very thin, it does not insulate the animal well, and therefore it is considerably warmer in comparison with the surroundings. That is why thermal cameras are ideal for detecting them. The commercially available manual thermal imagers, however, are not fully satisfactory as a large area of the field is impossible to cover from the field’s edge. Besides, if a person in a combine harvester, for example, holds the camera, there is no guarantee that the fawn hiding in the thick grass or grain will be detected from this particular distance and angle. The thermal radiation of the animal may not penetrate through the grass either. In addition to this, the fawn can be located by the thermal imaging camera up to a distance of several metres and the reaction time of man or machine does not guarantee that the fawn will be saved.
Use of thermal imagers in search for game in fields
The solution to this problem is the use of thermal imaging systems that can scan the field quickly and easily from a great height, since the thermal imagers are attached to helicopters or drones. Such a device can map the desired site in a very short period of time; an area of one hectare can be mapped, according to the user’s experience, in less than 10 minutes. The thermal imaging camera is designed for recognition of corresponding partial regions of the acquired thermographic images, and with it, the acquired images can be assembled into an overall image by overlapping the corresponding partial regions and displayed. The acquisition of the images preferably takes place during the swivelling of the thermal imaging camera over the solid angle region of the desired overall image. The ideal viewing distance is considered to be 30 metres, and a viewing angle of 34 degrees (view perpendicular to the surface of the field). In this case, the view of the fawn is not covered with vegetation and thermal radiation is therefore not absorbed. Consequently, the thermal imager provides a clear image of the animal. Unfortunately, as with most thermal diagnostic applications, lightning conditions, especially direct sunlight, may affect the search results. However, it is still possible to use the system even in summer days on the condition that the sun is not shining directly down on the surface which is being monitored. Workswell WIRIS is the ideal medium for such a control. The Workswell WIRIS system is a lightweight, compact system that combines a camera for visible spectrum, thermal camera, and a control unit that allows the user to check a large area of a field or meadow during a very short time. In flight it allows the possibility to watch live images from the two cameras, capture a fully radiometric video or sequence of images of the entire flight. Records can then be analysed via the Workswell CorePlayer software with advanced measurement functions. The user can also easily and swiftly create desired protocols.
The Workswell WIRIS system allows the possibility to remotely switch modes and by doing so define alarm states, i.e. objects (in this case game) of temperature exceeding the expected limit. These identified objects are highlighted by a selected contrasting colour in thermogram where the brighter colours indicate warmer temperatures and may therefore be identified quickly. The high sensitivity of the system is also achieved by manually setting the range of temperatures in order to ensure a clear identification of such hot objects. Each colour of the chosen palette represents the same temperature and does not automatically change when the temperature of the surface which is being monitored changes, as is the case of more simple systems. The GPS locator is another essential part of the system which monitors the location of game in a field. In addition to all temperature data and information on camera settings, the Workswell WIRIS system also stores the GPS coordinates to the thermogram. This allows the user ease of orientation. During harvest, the user can quickly and easily find the baby animal and carry it to safety or simply avoid it.
Farmers, gamekeepers and environmentalists have been trying to tackle a serious issue, i.e. the death of animals (such as fawns) due to the industrialisation of the harvest and the inability to detect animals in the fields. Fortunately, this problem can be solved from the air by using the camera control system. A classic camera which detects the visible spectrum serves, in this case, only as auxiliary orientation means. The real help and measurement means here is the thermal imaging system that detects thermal radiation of the animal. Consequently, the situation in the field can be easily monitored and detected straight from the air thanks to the thermal imaging system being attached to a drone and controlled by several switches of a standard RC controller. It is also connected with a GPS locator. Remotely, it is possible to view and store fully radiometric data. Even though this system cannot save all the young game, it can save the great majority of them and thus avoid the undesirable consequences of this ecological problem.