Aerial surveys have always significantly contributed to the accurate mapping of certain geographical phenomena. Remote sensing opened up new perspectives in nature monitoring with state-of-the-art technical solutions using modern onboard recording equipment. We developed the technical background and the methodology that supports detailed and cost-effective monitoring of a network of natural areas, thereby detecting temporal changes in the spatial pattern of land cover, species, biodiversity, and other natural features. In this article, we share our experiences of the technical background, geometric accuracy and results of comparisons with selected Copernicus Land Monitoring products and an Ecosystem Map based on the testing of our methodology at 25 sites in Hungary. We combined a high-spatial-resolution aerial remote sensing service with field studies to support an efficient nature conservation monitoring network at 25 permanent sites. By analyzing annually (or more frequently) orthophotos taken with a range of 0.5–5 cm spatial resolution and 3D surface models of aerial surveys, it is possible to map the upper canopy of vegetation species. Furthermore, it allows us to accurately follow the changes in the dynamics at the forest edge and upper canopy, or the changes in species’ dominance in meadows. Additionally, spatial data obtained from aerial surveys and field studies can expand the knowledge base of the High-Resolution Aerial Monitoring Network (HRAMN) and support conservation and restoration management. A well-conducted high-resolution survey can reveal the impacts of land interventions and habitat regeneration. By building the HRAMN network, nature conservation could have an up-to-date database that could prompt legal processes, establish protection designation procedures and make environmental habitat management more cost-effective. Landscape protection could also utilize the services of HRAMN in planning and risk reduction interventions through more reliable inputs to environmental models.

The procedure is practically an optimization method, during which it is assumed that the gamma dose values detected at different points above the area come from the background radiation and from a single source found in the area. Accordingly, the procedure searches within the area for a geographical coordinate for which the distance law for the spatial propagation of radiation will be true. In order to validate the procedure, we performed measurements in a test area in such a way that all parameters of the source, including its location, were well defined. However, these data were not taken into account during the processing, i.e., the search procedure did not have these data. We can estimate the radiation position without a positional parameter. The exact coordinate and the intensity of the radiating sample were only used when checking the results. We have also applied the method to the raw data of our experiments carried out in the past if we used one source for them. The results confirmed our assumptions. The method is suitable for determining the starting parameters of more complex processes that can even detect multiple sources, but assuming one source, it has proven to be a reliable analytical method on its own.

High altitude aerial surveys have the potential to improve disturbance-free data collection in wildlife research, but previously, bird species were not recognizable in high-altitude orthophotos. This method of aerial surveying is effective and can be repeated frequently due to its low cost; it also has the additional advantage of being able to monitor the status of protected areas. In the case of waterbirds, due to the low vegetation coverage, aerial remote sensing is an exceptionally effective technique for surveying populations and detecting nests. Aerial surveys made at low altitudes can cause serious stress for birds. The method we developed and employed is unlikely to be detected by either ground-based or nesting birds but is far more reliable compared to the low-resolution imaging methods and to the evaluation of non-georeferenced photo series. The modern sensors and photogrammetric procedures enable the use of the present method worldwide; furthermore, the large-scale ortho image-derived information has become obtainable more frequently. Direct georeferencing makes the field geodetic survey unnecessary. Orthophotos with a 0.7 cm spatial resolution allow us to reliably identify even the individuals of smaller species, and by the use of oblique images, they can be tracked from two or four different directions.

Abstract. Aim. Accurate knowledge of the extent and local distribution of pollution plays a key role in many areas of life.Method. Although there are many well-known and generally-accepted methods for obtaining the intended data, these methods do not give a satisfactory result in cases when it is necessary to determine the exact parameters of pollution quickly and in a relatively small area (e.g. an industrial zone of several square kilometers, a residential area, etc.) and to determine changes in these parameters as expressed numerically. Small UAVs (multicopter with fixed or rotating wing) were equipped with sensitive detectors for gamma rays and polluting gases, including the assignation of flight data coordinates to the measured data. Such informational groupings provide the opportunity to determine the distribution of radiation or air polluting gases. Using this method, it is possible to identify and localise illegally-stored or illegally-released gamma ray emitting materials, continuously monitor pollution caused by chemical disasters and determine the spatial distribution of pollution.Results. The article presents systems based on practical experiments, which, in the case of using a gamma detector, allow the localisation of objects using low radiation doses along with a high-quality map of gamma radiation in a specific area; and, in the case of gas sensors, the visualisation of the spatial distribution of a polluting gas. The method is used primarily in the field to detect gamma emitters with low activity or to analyse the emission of industrial facilities with the emission of pollutants.Conclusion. The combination of spatial coordinates with remote sensing data comprises an effective meas-urement method. The developed system is generally applicable for mobile platforms equipped with sensors. The systems are designed to provide fast, efficient and reliable measurements that can be used for both detection and control. The type of pollutants to be measured depends on the sensors used. The experiments also indicate that, when replacing the used sensors, it may be necessary to change the processing of the measured data in accordance with the characteristics of the particular sensor; however, in general, data processing and visualisation of the results can be carried out in practice.

Several dose distribution maps were obtained using a gamma radiation detector mounted to a drone. Based on the results and experience of the experiments, the shortcomings of the system and the possibilities for further development were identified. The primary goal of the development was to create a more compact, easy-to-carry, and easy-to-install system with increased sensitivity, which was achieved by several different methods and their combinations. During the discrete measurement procedure, the aim was to decrease the detection threshold, +0.005 to +0.007 μS/h measured above the background radiation. The increase in sensitivity was based on the characteristic energy spectrum of radiative materials. We took advantage of the fact that the radiating samples do not evenly increase the amount of gamma radiation over the entire energy spectrum. During the processing of the measurement data, we performed a comparison with the background radiation in the vicinity of the energy peaks characteristic of the sample and its decay products. This provides a better signal-to-noise ratio, thus enabling a more sensitive detection procedure. An important feature of our method is that in the traditional intensity curve displayed as a function of flight time only noise is visible, therefore one cannot directly conclude the presence of the sample. However, our method is clearly able to identify the location of the searched source at a height of 8 m with a continuous flight speed of 2 m/s using a 500 μS/h activity sample (as measured at a distance of 0.1 m from the sample). The increase in sensitivity allows either a higher scanning height (approximately +1 to 2 m) or, in the case of the same aircraft at the same altitude, a larger area from one take-off. Of course, the scan height or scan speed can increase significantly if the activity of the source being sought is high. In our experiments, we used a natural uranium mineral (Autunite) with activity far below that of artificially produced isotopes. In the series of our experiments, we also covered the detection of several sources, which modeled the possibility of mapping scattered active sources. The main advantages of the system developed and presented by us over the survey procedures used in practice is that a large area can be mobilized easily, without the risk of a human operator in the field, and the survey of a large area can be carried out at a low cost. The purpose of the system is to detect the presence of the source and to localize it to such an extent that the localization can then be easily refined by manual or other ground procedures. As we do not aim for positioning accuracy by centimeter, standard GPS localization is sufficient for the measurements. During the measurements, the geographical coordinates are interpreted in the GWS’84 system. The coordinates of the latitude and longitude circles are also shown in this system in the figures presented.

The power supply of quadcopters is provided for by a battery. Flight time depends on total weight and on battery capacity. The most widespread one is the lithium polymer (LiPo) battery. Its advantage is that it has a high electricity transmission ability and a very good mass-capacity ratio. In case of a critical capacity level it is important for the quadcopter to land as soon as possible. Landing speed however is limited. The so-called vortex wave state (vortex ring state) appears at landing. The vortex ring state was first observed at helicopters. The reason for the phenomenon is that at descent the air flow speed arriving from below at a vertical descent approximates the speed of the air currents generated by the rotors. In this moment, the air flowing through the rotors creates a closed vortex wave and a low-pressure spot is created. In this case, the perfomance of the rotors drops, the quadrocopter might become instable and uncontrollable. This phenomenon can be avoided by limiting descent speed. In the article, I tested how to increase descent speed to be able to land safely as fast as possible, using the least possible energy.