Effectiveness of Sentinel-2 in Multi-Temporal Post-Fire Monitoring When Compared with UAV Imagery

Luís Pádua,Telmo Adão,Emanuel Peres,Nathalie Guimarães,Joaquim J Sousa,António Sousa

doi:10.3390/ijgi9040225

Abstract

Unmanned aerial vehicles (UAVs) have become popular in recent years and are now used in a wide variety of applications. This is the logical result of certain technological developments that occurred over the last two decades, allowing UAVs to be equipped with different types of sensors that can provide high-resolution data at relatively low prices. However, despite the success and extraordinary results achieved by the use of UAVs, traditional remote sensing platforms such as satellites continue to develop as well. Nowadays, satellites use sophisticated sensors providing data with increasingly improving spatial, temporal and radiometric resolutions. This is the case for the Sentinel-2 observation mission from the Copernicus Programme, which systematically acquires optical imagery at high spatial resolutions, with a revisiting period of five days. It therefore makes sense to think that, in some applications, satellite data may be used instead of UAV data, with all the associated benefits (extended coverage without the need to visit the area). In this study, Sentinel-2 time series data performances were evaluated in comparison with high-resolution UAV-based data, in an area affected by a fire, in 2017. Given the 10-m resolution of Sentinel-2 images, different spatial resolutions of the UAV-based data (0.25, 5 and 10 m) were used and compared to determine their similarities. The achieved results demonstrate the effectiveness of satellite data for post-fire monitoring, even at a local scale, as more cost-effective than UAV data. The Sentinel-2 results present a similar behavior to the UAV-based data for assessing burned areas.

Highlights

In recent years, forest fires have received increasing attention due to their effects on climate change and ecosystems
The normalized difference vegetation index (NDVI) from the Sentinel-2 Multispectral Instrument (MSI) data was compared with Unmanned aerial vehicles (UAVs)-based high-resolution data at different spatial resolutions (0.25, 5 and 10 m) to access their similarities
The results demonstrated the effectiveness of satellite data for post-fire monitoring, even at a local scale

Summary

Introduction

Forest fires (i.e., large and destructive fires that spread over a forest or area of woodland) have received increasing attention due to their effects on climate change and ecosystems. Vary in scale and impacts and are inherent to terrestrial ecosystems [1]. Do fires over forests affect the country, but the combination of environmental factors and human settlement may cause harm to people or damage property or the environment [4]. Several factors contribute to the country being so severely affected: the Mediterranean climate, which benefits fuel accumulation and dryness along with the existence of flammable vegetation types; high ignition density; poor fire-suppression capabilities; and institutional instability [5]. In the Portuguese case, this awareness is increasing, especially in the north and in the center of the country [6]

Results

Discussion

Conclusion