Abstract
This study explores the potential of Synthetic Aperture Radar (SAR) to aid Unmanned Aerial Vehicle (UAV) navigation when Inertial Navigation System (INS) measurements are not accurate enough to eliminate drifts from a planned trajectory. This problem can affect medium-altitude long-endurance (MALE) UAV class, which permits heavy and wide payloads (as required by SAR) and flights for thousands of kilometres accumulating large drifts. The basic idea is to infer position and attitude of an aerial platform by inspecting both amplitude and phase of SAR images acquired onboard. For the amplitude-based approach, the system navigation corrections are obtained by matching the actual coordinates of ground landmarks with those automatically extracted from the SAR image. When the use of SAR amplitude is unfeasible, the phase content can be exploited through SAR interferometry by using a reference Digital Terrain Model (DTM). A feasibility analysis was carried out to derive system requirements by exploring both radiometric and geometric parameters of the acquisition setting. We showed that MALE UAV, specific commercial navigation sensors and SAR systems, typical landmark position accuracy and classes, and available DTMs lead to estimate UAV coordinates with errors bounded within ±12 m, thus making feasible the proposed SAR-based backup system.
Highlights
This study is devoted to explore the potentials of synthetic aperture radar (SAR) and InterferometricSAR (InSAR) to aid unmanned aerial vehicle (UAV) navigation
Requirements in Table 3 can be fulfilled by commercial systems, e.g., Pico-SAR radar produced by Selex-ES [22]; medium-altitude long-endurance (MALE) UAV [10] such as Predator B, Global Hawk and Gray Eagle, which carry a Pico-SAR radar; navigation grade class inertial measurement unit (IMU) such as LN-100G IMU [20]; any radar altimeter (RALT)
This problem can affect in particular the MALE UAV class during a long endurance flight
Summary
SAR (InSAR) to aid unmanned aerial vehicle (UAV) navigation. The feasible use of a UAV for a certain application relies on the accuracy and robustness of the navigation system. The navigation of a UAV is controlled by the inertial navigation system (INS), which exploits different sensors such as inertial measurement unit (IMU), radar altimeter (RALT) and global positioning system (GPS) receiver. These sensors allow the UAV to measure the status vectors of the aircraft (position, velocity, acceleration, Euler attitude angle and rates) needed to infer the actual trajectory with enhanced accuracy. The INS defines the commands needed to change the status vectors in order to guide the aircraft along the mission reference trajectory, or can be used to provide geo-referenced products acquired onboard for ground control point free applications [1]
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