Using Unmanned Aerial Vehicles in Postfire Vegetation Survey Campaigns through Large and Heterogeneous Areas: Opportunities and Challenges

TLDR

The study assessed the feasibility of using drones to capture ultra‑high‑resolution multispectral orthomosaics for monitoring large, heterogeneous post‑fire vegetation. An octocopter equipped with a Parrot SEQUOIA multispectral camera surveyed a 3000‑ha megafire perimeter, and the resulting raw imagery, orthomosaic, and processing requirements were evaluated and compared to high‑resolution WorldView‑2 satellite data. The drone orthomosaic revealed banding noise and GPS synchrony problems but achieved sub‑30‑cm XY and sub‑55‑cm Z accuracy, offering richer spatial detail than WorldView‑2 and proving a viable tool for assessing post‑fire vegetation regeneration.

Abstract

This study evaluated the opportunities and challenges of using drones to obtain multispectral orthomosaics at ultra-high resolution that could be useful for monitoring large and heterogeneous burned areas. We conducted a survey using an octocopter equipped with a Parrot SEQUOIA multispectral camera in a 3000 ha framework located within the perimeter of a megafire in Spain. We assessed the quality of both the camera raw imagery and the multispectral orthomosaic obtained, as well as the required processing capability. Additionally, we compared the spatial information provided by the drone orthomosaic at ultra-high spatial resolution with another image provided by the WorldView-2 satellite at high spatial resolution. The drone raw imagery presented some anomalies, such as horizontal banding noise and non-homogeneous radiometry. Camera locations showed a lack of synchrony of the single frequency GPS receiver. The georeferencing process based on ground control points achieved an error lower than 30 cm in X-Y and lower than 55 cm in Z. The drone orthomosaic provided more information in terms of spatial variability in heterogeneous burned areas in comparison with the WorldView-2 satellite imagery. The drone orthomosaic could constitute a viable alternative for the evaluation of post-fire vegetation regeneration in large and heterogeneous burned areas.