Early-Stage Deforestation Detection in the Tropics With L-band SAR

Abstract

Polarimetric characteristics of early-stage deforestation areas were examined with L-band synthetic aperture radar (SAR) to develop a forest early warning system. Time series of PALSAR-2/ScanSAR data and Landsat data were used to examine the differences in detection timing of deforestation in the most active deforestation sites in Peru and Brazil. The γ 0 H H value increased by 0.8 dB on average for areas undergoing early-stages of deforestation, in which felled trees were left on the ground. The detection timing was almost the same as that of using the optical sensor. On the other hand, the γ 0 H V value does not show significant γ 0 change at this early-stage of deforestation. The γ 0 H V value started to decrease 1-1.5 months after the deforestation was detected by Landsat. The γ 0 H V value decreased by 1.5-1.6 dB, 4-5 months after the deforestation. To understand the radar backscattering mechanism at the early-stage deforestation sites, field experiments were carried out 2-16 days after the PALSAR-2/fullypolarimetric observations. The early-stage deforestation sites revealed 1.1-2.5 dB and 2.9-4.0 dB increases for σ 0 H H and σ 0 su rface , respectively. This can be explained by the direct (single bounce) scattering from felled trees left on the ground. The sites in which felled trees were removed and the surfaces were flattened showed 5.2-5.3 dB and 5.3-5.5 dB decreases for σ 0 H V and σ 0 vo lu m e , respectively. This can be explained by the lower sensitivity of the HV polarization to both the branches remaining on the ground and the surface roughness, along with its increased sensitivity to the forest biomass. We conclude that an increase in L-band γ 0 H H is a good indicator for detecting early-stage deforestation sites, where felled trees are left on the ground, while γ 0 H V may be useful for detecting later-stage deforestation sites.

Estado da Arte do Sensoriamento Remoto por Radar: Fundamentos, Sensores, Processamento de Imagens e Aplicações

“…Isso ocorre porque os detritos de madeira (troncos e galhos) que ficam no solo aumentam os processos de retroespalhamento do radar para valores superiores aos encontrados nas florestas primárias circundantes (ALMEIDA-FILHO et al, 2005). Pesquisa conduzida por Watanabe et al (2018)…”

Temporal Decorrelation of C-Band Backscatter Coefficient in Mediterranean Burned Areas

“…One should notice that temporal decorrelation was observed not only over fire-disturbed areas and C-band data. Similar effects were observed for L-band data over areas affected by logging [37]. Therefore, a better understanding of the temporal decorrelation effects and its sources is needed to improve SAR-based burned area mapping algorithms.…”

Environmental Violation Fines Growth in the Northern Region of Santa Catarina State, Brazil

“…This position reinforce the importance of having a monitoring system based on remote sensing images. Such initiatives are already implemented in other Brazilian biomes (Nicolle & Leroy 2017;Watanabe et al, 2018;Warren-Thomas et al, 2018;Reiche et al, 2018;Bouvet et al, 2018;Silva et al, 2018;Grecchi et al, 2017;Carvalho et al, 2017). Thus, based on the scores presented in Figure 3, it could be demonstrated that the categories related to Fauna, Pollution and Others had a number of environmental violations smaller than Flora.…”