Abstract
Abstract. This paper will introduce the goals, concept and results of the project named CLOSE-SEARCH, which stands for ’Accurate and safe EGNOS-SoL Navigation for UAV-based low-cost Search-And-Rescue (SAR) operations’. The main goal is to integrate a medium-size, helicopter-type Unmanned Aerial Vehicle (UAV), a thermal imaging sensor and an EGNOS-based multi-sensor navigation system, including an Autonomous Integrity Monitoring (AIM) capability, to support search operations in difficult-to-access areas and/or night operations. The focus of the paper is three-fold. Firstly, the operational and technical challenges of the proposed approach are discussed, such as ultra-safe multi-sensor navigation system, the use of combined thermal and optical vision (infrared plus visible) for person recognition and Beyond-Line-Of-Sight communications among others. Secondly, the implementation of the integrity concept for UAV platforms is discussed herein through the AIM approach. Based on the potential of the geodetic quality analysis and on the use of the European EGNOS system as a navigation performance starting point, AIM approaches integrity from the precision standpoint; that is, the derivation of Horizontal and Vertical Protection Levels (HPLs, VPLs) from a realistic precision estimation of the position parameters is performed and compared to predefined Alert Limits (ALs). Finally, some results from the project test campaigns are described to report on particular project achievements. Together with actual Search-and-Rescue teams, the system was operated in realistic, user-chosen test scenarios. In this context, and specially focusing on the EGNOS-based UAV navigation, the AIM capability and also the RGB/thermal imaging subsystem, a summary of the results is presented.
Highlights
The use of Unmanned Aerial Vehicles (UAVs) —more in general, Unmanned Aerial Systems (UASs)— for SAR operations is not new and has been traditionally fed by developments made in other fields
Real-Time Kinematic (RTK) navigation is characterized by providing centimeter-level accuracy: the existing navigation subsystem was used as a reference for the validation of the EGNOS-based navigation subsystem, which was a genuine project development
This subsystem provides a direct link between the UA and the CS and its quality of service depends of Signal-to-Noise Ratio (SNR), which worsens with distance or obstacles
Summary
The use of Unmanned Aerial Vehicles (UAVs) —more in general, Unmanned Aerial Systems (UASs)— for SAR operations is not new and has been traditionally fed by developments made in other fields. As a example of that, we recall the UAVs used in the Iraq and Afghanistan wars were deployed to find people trapped in New Orleans buildings devastated by Hurricane Katrinas flood waters Those platforms were equipped with thermal imaging systems to detect the body heat of storm survivors. Thinking on the general SAR context, when a small plane crashes in a remote area, or a fishing boat is lost at sea, or a hurricane devastates a region, or a person gets lost while he/she was hiking, SAR teams must scan vast areas in search for victims evidence or wreckage For this purpose, UAVs equipped with thermal or other sensors can be programmed to fly predefined search patterns at low altitudes —30 m to 150 m—, transmitting realtime imagery back to a ground station via a data link. In figure 2, the UAV and the GCS are presented on its final CLOSE-SEARCH version during the final test campaign in March 2012
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