The close-search project: uav-based search operations using thermal imaging and egnos-sol navigation
This paper introduces and describes the goals, concept and overall approach of the European 7th Framework Programme's project named CLOSE-SEARCH, which stands for 'Accurate and safe EGNOS-SoL Navigation for UAV-based low-cost SAR operations'. The goal of CLOSE-SEARCH is to integrate in a helicopter-type Unmanned Aerial Vehicle (UAV), a thermal imaging sensor and a multi-sensor navigation system (based on the use of a Barometric Altimeter (BA), a Magnetometer (MAGN), a Redundant Inertial Navigation System (RINS) and an SBAS-enabled GNSS receiver) with an Autonomous Integrity Monitoring (AIM) capability, to support the search component of Search-And-Rescue (SAR) operations in remote, difficult-to-access areas and/or in time critical situations. The proposed integration will result in a Hardware and Software prototype that will demonstrate an end-to-end functionality, that is to fly in patterns over a region of interest (possibly inaccessible) during day or night and also under adverse weather conditions,and locate there disaster survivors or lost people through the detection of the body heat In other words, CLOSE-SEARCH strives to be a low-cost and robust system that searches for distressed people in situations where only an approximate knowledge of their whereabouts is available. Finally, it is also the goal of CLOSE-SEARCH to demonstrate the added value of a future multi-constellation augmented GNSS configuration (Galileo/GPS-EGNOS or Galileo/GPS-SoL). Two key target attributes of the proposed concept are first the overall low-cost in the context of SAR (so it can be massively implemented and integrated into existing SAR operation chains) and second the ultra-safe navigation. The latter concept is of the utmost importance when dealing with autonomous platforms, as in this case, enhanced system robustness against undesired failures is needed. In addition, nowadays the employment of UAVs is closely observed by the public as well as the state-authorities and therefore an accident might be socially harmful. Although we are aware that ultra-safe navigation is just a part if the problem -safety must be ensured at several levels (redundant communication links, duplicated mechanical components, etc. ) our primary focus is the navigational aspect. The ultra-safe concept is twofold: firstly, it embodies the necessary -though not sufficient, as already mentioned- condition of integrating a manifold of navigation sensors in a way that the precision, accuracy and reliability can be estimated. Secondly, the estimates of precision, accuracy and reliability shall meet some [rather demanding] criteria. Thus, the proposed prototype requires the integration of EGNOS and [future] Galileo/GPS SoL services, 3D geospatial databases (Digital Surface Model, DSM), RINS/GNSS close-coupling algorithms, as well as UAS, communications and remote-sensing technologies to achieve this goal. It also requires a mechanism to measure and manage the achieved reliability by this multi-sensor approach which is the so-called Autonomous Integrity Monitoring (AIM). This paper will identify the technical challenges of the proposed approach, from navigating with a BA/MAGN/RINS/GPS-EGNOS-based integrated system to the interpretation of thermal images for person identification. Moreover, the AIM approach will be described together with the proposed integrity requirements. Finally, this paper will show some results obtained in the project during the first test campaign performed on November, 25th 2010. On that day, a prototype was flown in three different missions to assess its high-level performance and to observe some fundamental mission parameters as the optimal flying height and flying speed to enable body recognition. The second test campaign is scheduled for early September, 2011. Hence, this paper will also describe the proposed tests and some preliminary results.