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Orthorectification of helicopter-borne high resolution experimental burn observation from infra red handheld imagers

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Ronan Paugam, Martin J. Wooster, William E. Mell, Mélanie C. Rochoux, Jean Baptiste Filippi, Gernot Rücker, Olaf Frauenberger, Eckehard Lorenz, Wilfrid Schroeder, Bruce Main, Navashni Govender

Original languageEnglish
Article number4913
JournalREMOTE SENSING
Volume13
Issue number23
DOIs
Published1 Dec 2021

Bibliographical note

Funding Information: Funding: This work has received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie, grant H2020-MSCA-IF-2019-892463. Parts of this work were also supported by the NERC, grant NE/M017729/1 made by the UK’s Natural Environment Research Council. The KNP14 Fieldwork campaign was also supported by the Ministry of Economy of Bavaria (Az. 20-08-3410.2-05-2012) and a START grant (www.start.org, last access date: 24 November 2021). Funding Information: This work has received funding from the European Union?s Horizon 2020 research and innovation program under the Marie Sk?odowska-Curie, grant H2020-MSCA-IF-2019-892463. Parts of this work were also supported by the NERC, grant NE/M017729/1 made by the UK?s Natural Environment Research Council. The KNP14 Fieldwork campaign was also supported by the Ministry of Economy of Bavaria (Az. 20-08-3410.2-05-2012) and a START grant (www.start.org, last access date: 24 November 2021).The authors would like to dedicate this paper to the memory of our co-author Eckehard Lorenz, principal investigator of the FireBird mission, who sadly passed away before the manuscript could be completed. The authors would also like to thank Anja Hoffman, the South African National Parks (SANParks) and the fire team from Kruger National Park for the organization of the experimental burns as well as the various staff and students of the Department of Geography, King?s College London, and other visitors, who graciously assisted with the different aspects of the fieldwork. Thanks also to the Biblioth?que Francois Mitterrand in Paris for opening its door to academics forced to pause. Publisher Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

King's Authors

Abstract

To pursue the development and validation of coupled fire-atmosphere models, the wildland fire modeling community needs validation data sets with scenarios where fire-induced winds influence fire front behavior, and with high temporal and spatial resolution. Helicopter-borne infrared thermal cameras have the potential to monitor landscape-scale wildland fires at a high resolution during experimental burns. To extract valuable information from those observations, three-step image processing is required: (a) Orthorectification to warp raw images on a fixed coordinate system grid, (b) segmentation to delineate the fire front location out of the orthorectified images, and (c) computation of fire behavior metrics such as the rate of spread from the time-evolving fire front location. This work is dedicated to the first orthorectification step, and presents a series of algorithms that are designed to process handheld helicopter-borne thermal images collected during savannah experimental burns. The novelty in the approach lies on its recursive design, which does not require the presence of fixed ground control points, hence relaxing the constraint on field of view coverage and helping the acquisition of high-frequency observations. For four burns ranging from four to eight hectares, long-wave and mid infra red images were collected at 1 and 3 Hz, respectively, and orthorectified at a high spatial resolution (<1 m) with an absolute accuracy estimated to be lower than 4 m. Subsequent computation of fire radiative power is discussed with comparison to concurrent space-borne measurements.

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