[EMAIL_ADDRESS] (A.M.); sven.gotovac@fbesb. certain the subject was recently located. In that case, this point is called the Last Known Position (LKP) [2]. The next step in planning is defining the area around the IPP that will be observed [5; 6]. This area is usually defined using statistical data gathered from several search and rescue missions and stored in a unified database--the International Search and Rescue Incident Database (ISRID). Based on the type of person that has been lost, summary statistics are available for the Euclidean distance from IPP, the track offset, the dispersion angle, find location, scenario, mobility and survivability [7]. An area definition based on Euclidean distance from the IPP (the so-called \"Ring\" approach) is not the only way to define the starting area that will be investigated [5], but it is probably the simplest, and therefore the most commonly used, approach (Figure 1). It is worth noticing that estimation of LKP can be based on a mobile phone positioning approach [8; 9; 10]. A mobile phone's position can be derived from the measurement of its signals. The most important measurements are propagation time, angle of arrival and carrier phase. Each measurement defines a locus on which the mobile phone must lie. The point at which the loci from multiple measurements intersect defines the position. Use of a passive positioning method to locate 4G mobile phones in post-disaster scenarios by capturing the random access preamble was proposed in [11]. Furthermore, a smartphone can be equipped with an application that, without a signal, emits a Wi-Fi signal which, in turn, acts as a distress beacon over a distance of several kilometers [12]. However, all approaches based on the positioning of a mobile phone signal have some limitations. First, network signals should be available at the search area, which is quite often a problem in non-urban areas (or an application should be pre-installed, such as in [12]). The second problem is related to the fact that a lost person should have a mobile phone with still working batteries (and searchers should know that phone number). The third problem might be the time needed for getting permissions to use data of the network provider to reconstruct the last known approximate location of the mobile phone. Therefore, the most likely scenario is a visual search of the terrain by rescuers or drones. Around the IPP, segments with similar types of terrain are defined and each is divided into areas that can be searched by some assigned resources (searchers, dogs, drones, etc.). As already stated, the GIS software is the basis for visualizing these areas and can also be used for situational awareness and basic incident management tasks [13]. The available online maps used in GIS may be quite old and sometimes misleading. Changes can be significant when comparing maps taken during different times of the year. Moreover, there is always the possibility that some new roads, houses or other infrastructures have been built. These facts affect the planning and search priorities. To  
Figure 1: Example of a standard search and rescue (SAR) scenario based on Euclidean distance from the initial planning point (IPP). provide the best possible input for the planners and search teams, up-to-date information about the terrain is of essential importance. This is the first reason for introducing and proposing an approach that will incorporate aerial images of the area of interest taken at the time of the mission. Another reason is that these images (if taken with sufficient resolution) can be used for the automatic detection of humans [14; 15]. In [16], a fixed-wing unmanned aerial vehicle (UAV) with a DLR Modular Airborne Camera System (MACS) and Wi-Fi-based 10 Mbit/s data downlink was tested for real-time mapping. The authors reported a typical operation of the overall system at a height of 200 m above the ground and at a speed of 80 km/h with a frame rate of 2 Hz. For data downlink, a civil Wi-Fi-based radio link with pointing antennas on both sides was used.