High-resolution imaging of hydrothermal heat flux using optical and thermal Structure-from-Motion photogrammetry

Journal of Volcanology and Geothermal Research
By: , and 

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Abstract

Quantifying hydrothermal heat flux at meter-scale resolution over N0.25 km2 is required to bridge in-situ heat flux and satellite-based measurements. We advance a methodology that blends ground-based daytime optical and nighttime thermal infrared (TIR) imagery using Structure-from-Motion photogrammetry to map radiant hydrothermal heat flux over these scales at sites with low signal-to-noise ratios that would otherwise be difficult to characterize using, for example, unmanned aerial systems. The improved method uses a computerized telescopic mount to relocate and align daytime optical acquisitions with nighttime TIR imagery, thereby enabling TIR acquisition from multiple camera orientations positioned throughout a study area. This facilitates mapping of thermal features at sites of varying size and complexity and helps to ameliorate topographic occlusion effects and geometric distortions that can bias radiant hydrothermal heat flux estimates derived from the resulting orthorectified thermal maps. We assessed detection thresholds of this method at three sites across central California, which range in size, topography, and heat flux conditions. We found that blending of optical and thermal acquisitions successfully detected anomalous heat flux, even in cases where temperatures were only slightly greater than background. This approach might be applied to a variety of volcanic and hydrothermal systems to quantify the spatial distribution of heat flux, and how this may relate to factors such as the distribution of ground fractures and lava flow rheology.
Publication type Article
Publication Subtype Journal Article
Title High-resolution imaging of hydrothermal heat flux using optical and thermal Structure-from-Motion photogrammetry
Series title Journal of Volcanology and Geothermal Research
DOI 10.1016/j.jvolgeores.2020.106818
Volume 393
Year Published 2020
Language English
Publisher Elsevier
Contributing office(s) Volcano Science Center
Description 106818
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