Abstract
The use of unmanned aerial vehicles with multiple onboard sensors has grown significantly in tasks involving terrain coverage such as environmental and civil monitoring, disaster management, and forest fire fighting. Many of these tasks require a quick and early response, which makes maximizing the land covered from the flight path a challenging objective, especially when the area to be monitored is irregular, large and includes many blind spots. Accordingly, state-of-the-art total viewshed algorithms can be of great help to analyze large areas and find new paths providing maximum visibility. This article shows how the total viewshed computation is a valuable tool for generating paths that provide maximum visibility during a flight. We introduce a new heuristic called visibility-based path planning (VPP) that offers a different solution to the path planning problem. VPP identifies the hidden areas of the target territory to generate a path that provides the highest visual coverage. Simulation results show that VPP can cover up to 98.7% of the Montes de Malaga Natural Park and 94.5% of the Sierra de las Nieves National Park, both located within the province of Malaga (Spain) and chosen as regions of interest. In addition, a real flight test confirmed the high visibility achieved using VPP. Our methodology and analysis can be easily applied to enhance monitoring in other large outdoor areas.
Highlights
T HE analysis of visibility is of paramount importance in Geographic Information System (GIS) software
Once all necessary data structures have been defined, we can present the general workflow for any path and Digital Elevation Model (DEM) to simulate the camera behaviour during flight: 1) For each waypoint in the flight path, do: a) Fill RS based on the current visibility and PL-CVS map. b) Fill angle of view (AOV) according to the set of consecutive sectors with the highest overall weight. c) For each point in the DEM, do: i) Compute the angular difference (Ad) and Euclidean distance (Ed) between the waypoint and the point
Path planning and visual coverage are still challenging problems as they depend to a large extent on the complexity and diversification of terrains
Summary
T HE analysis of visibility is of paramount importance in Geographic Information System (GIS) software. VPP shows the benefits of the total viewshed computation: we find several safe and flyable paths providing all-round visibility from the results obtained from a thorough visibility analysis that exposes the most hidden areas These results open the possibility of monitoring challenging regions of complex terrain using the onboard camera of a single UAV. As the generated path is composed of several waypoints, we provide a method to determine the direction of the onboard camera for each one, aiming to avoid overlapping visual areas of already monitored locations to increase the amount of terrain covered These images – taken throughout the flight – can be analysed in real time to alert local authorities in case of fire.
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