Explaining sentinel 2-based dNBR and RdNBR variability with reference data from the bird’s eye (UAS) perspective
Characterizing the spatial variability of the severity of wildfires is important to assess ecological and economic consequences and to coordinate mitigation strategies. Vegetation indices such as the differenced Normalized Burn Ratio (dNBR) have become a standard tool to assess burn or fire severity across larger areas and are being used operationally. Despite the frequent application of dNBR-like vegetation indices, it is not yet fully understood which variables exactly drive the variability in dNBR observed by multispectral satellites. One reason for this is the lack of high quality prefire information about vegetation structure and composition. Consequently, the influence of prefire vegetation composition and other potentially influential variables such as cast shadows has hardly been examined. Here, we use very high resolution Unmanned Aerial System (UAS) orthoimages collected briefly before and after the large wildfires in Central Chile in the fire season 2016/2017 to derive variables related to the pre- and postfire landscape composition and structure. The variables are used as predictors in Generalized Additive Models (GAM) to explain the spatial variability in dNBR and RdNBR pixel values as observed by Sentinel-2. Our models explain more than 80% and 75% of the variability in dNBR and RdNBR values, respectively, using a sparse set of five predictors. The results suggest that in our study area the largest fraction of variability in Sentinel-2 based dNBR and RdNBR values can be explained by variables related to the fraction of consumed canopy cover while the vegetation composition before the fire does not have a large influence on dNBR and RdNBR. Our results further suggest that cast-shadows of snags and standing dead trees with remaining crown structure have a notable influence on the dNBR signal which may have been underestimated so far. We conclude that spatially continuous, very high spatial resolution data from UAS can be a valuable data source for an improved understanding of the exact meaning of common vegetation index products, operationally used for monitoring the environment.
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Elsevier
2021-11-23T21:51:34Z
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Subjects: | UAS, dNBR variability, Wildfire, Sentinel-2, RdNBR, Shadows, |
Online Access: | https://repositorio.uchile.cl/handle/2250/182843 https://bibliotecadigital.infor.cl/handle/20.500.12220/32588 |
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dig-infor-cl-20.500.12220-325882023-06-20T14:43:16Z Explaining sentinel 2-based dNBR and RdNBR variability with reference data from the bird’s eye (UAS) perspective Fassnacht, Fabian Ewald Schmidt-Riese, Ephraim Kattenborn, Teja Hernández Palma, Héctor Jaime UAS dNBR variability Wildfire Sentinel-2 RdNBR Shadows Characterizing the spatial variability of the severity of wildfires is important to assess ecological and economic consequences and to coordinate mitigation strategies. Vegetation indices such as the differenced Normalized Burn Ratio (dNBR) have become a standard tool to assess burn or fire severity across larger areas and are being used operationally. Despite the frequent application of dNBR-like vegetation indices, it is not yet fully understood which variables exactly drive the variability in dNBR observed by multispectral satellites. One reason for this is the lack of high quality prefire information about vegetation structure and composition. Consequently, the influence of prefire vegetation composition and other potentially influential variables such as cast shadows has hardly been examined. Here, we use very high resolution Unmanned Aerial System (UAS) orthoimages collected briefly before and after the large wildfires in Central Chile in the fire season 2016/2017 to derive variables related to the pre- and postfire landscape composition and structure. The variables are used as predictors in Generalized Additive Models (GAM) to explain the spatial variability in dNBR and RdNBR pixel values as observed by Sentinel-2. Our models explain more than 80% and 75% of the variability in dNBR and RdNBR values, respectively, using a sparse set of five predictors. The results suggest that in our study area the largest fraction of variability in Sentinel-2 based dNBR and RdNBR values can be explained by variables related to the fraction of consumed canopy cover while the vegetation composition before the fire does not have a large influence on dNBR and RdNBR. Our results further suggest that cast-shadows of snags and standing dead trees with remaining crown structure have a notable influence on the dNBR signal which may have been underestimated so far. We conclude that spatially continuous, very high spatial resolution data from UAS can be a valuable data source for an improved understanding of the exact meaning of common vegetation index products, operationally used for monitoring the environment. 2021-11-23T21:51:34Z 2023-06-20T14:43:16Z 2021-11-23T21:51:34Z 2023-06-20T14:43:16Z 2021-11-23T21:51:34Z 2021 Artículo de revista International Journal of Applied Earth Observations and Geoinformation 95 (2021) 102262 10.1016/j.jag.2020.102262 https://repositorio.uchile.cl/handle/2250/182843 https://bibliotecadigital.infor.cl/handle/20.500.12220/32588 en http://creativecommons.org/licenses/by-nc-nd/3.0/us/ Attribution-NonCommercial-NoDerivs 3.0 United States Elsevier International Journal of Applied Earth Observations and Geoinformation |
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UAS dNBR variability Wildfire Sentinel-2 RdNBR Shadows UAS dNBR variability Wildfire Sentinel-2 RdNBR Shadows |
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UAS dNBR variability Wildfire Sentinel-2 RdNBR Shadows UAS dNBR variability Wildfire Sentinel-2 RdNBR Shadows Fassnacht, Fabian Ewald Schmidt-Riese, Ephraim Kattenborn, Teja Hernández Palma, Héctor Jaime Explaining sentinel 2-based dNBR and RdNBR variability with reference data from the bird’s eye (UAS) perspective |
description |
Characterizing the spatial variability of the severity of wildfires is important to assess ecological and economic consequences and to coordinate mitigation strategies. Vegetation indices such as the differenced Normalized Burn Ratio (dNBR) have become a standard tool to assess burn or fire severity across larger areas and are being used operationally. Despite the frequent application of dNBR-like vegetation indices, it is not yet fully understood which variables exactly drive the variability in dNBR observed by multispectral satellites. One reason for this is the lack of high quality prefire information about vegetation structure and composition. Consequently, the influence of prefire vegetation composition and other potentially influential variables such as cast shadows has hardly been examined. Here, we use very high resolution Unmanned Aerial System (UAS) orthoimages collected briefly before and after the large wildfires in Central Chile in the fire season 2016/2017 to derive variables related to the pre- and postfire landscape composition and structure. The variables are used as predictors in Generalized Additive Models (GAM) to explain the spatial variability in dNBR and RdNBR pixel values as observed by Sentinel-2. Our models explain more than 80% and 75% of the variability in dNBR and RdNBR values, respectively, using a sparse set of five predictors. The results suggest that in our study area the largest fraction of variability in Sentinel-2 based dNBR and RdNBR values can be explained by variables related to the fraction of consumed canopy cover while the vegetation composition before the fire does not have a large influence on dNBR and RdNBR.
Our results further suggest that cast-shadows of snags and standing dead trees with remaining crown structure have a notable influence on the dNBR signal which may have been underestimated so far. We conclude that spatially continuous, very high spatial resolution data from UAS can be a valuable data source for an improved understanding of the exact meaning of common vegetation index products, operationally used for monitoring the environment. |
format |
Artículo de revista |
topic_facet |
UAS dNBR variability Wildfire Sentinel-2 RdNBR Shadows |
author |
Fassnacht, Fabian Ewald Schmidt-Riese, Ephraim Kattenborn, Teja Hernández Palma, Héctor Jaime |
author_facet |
Fassnacht, Fabian Ewald Schmidt-Riese, Ephraim Kattenborn, Teja Hernández Palma, Héctor Jaime |
author_sort |
Fassnacht, Fabian Ewald |
title |
Explaining sentinel 2-based dNBR and RdNBR variability with reference data from the bird’s eye (UAS) perspective |
title_short |
Explaining sentinel 2-based dNBR and RdNBR variability with reference data from the bird’s eye (UAS) perspective |
title_full |
Explaining sentinel 2-based dNBR and RdNBR variability with reference data from the bird’s eye (UAS) perspective |
title_fullStr |
Explaining sentinel 2-based dNBR and RdNBR variability with reference data from the bird’s eye (UAS) perspective |
title_full_unstemmed |
Explaining sentinel 2-based dNBR and RdNBR variability with reference data from the bird’s eye (UAS) perspective |
title_sort |
explaining sentinel 2-based dnbr and rdnbr variability with reference data from the bird’s eye (uas) perspective |
publisher |
Elsevier |
publishDate |
2021-11-23T21:51:34Z |
url |
https://repositorio.uchile.cl/handle/2250/182843 https://bibliotecadigital.infor.cl/handle/20.500.12220/32588 |
work_keys_str_mv |
AT fassnachtfabianewald explainingsentinel2baseddnbrandrdnbrvariabilitywithreferencedatafromthebirdseyeuasperspective AT schmidtrieseephraim explainingsentinel2baseddnbrandrdnbrvariabilitywithreferencedatafromthebirdseyeuasperspective AT kattenbornteja explainingsentinel2baseddnbrandrdnbrvariabilitywithreferencedatafromthebirdseyeuasperspective AT hernandezpalmahectorjaime explainingsentinel2baseddnbrandrdnbrvariabilitywithreferencedatafromthebirdseyeuasperspective |
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