29 October 2014 Hemispherical directional reflectance factor using UAV and a hyperspectral camera, validation and crop field test
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Abstract
Small unmanned aerial vehicle (UAV) and a prototype hyperspectral imaging camera (HSI) was used to measure the hemispherical directional reflectance factor (HDRF) of a test field with known light scattering properties. The HSI acquires a burst of 24 images within two seconds and all of these images are acquired with different spectral content. By using the autopilot of the UAV, the flight can be preplanned so that the target area is optimally covered with overlapping images from multiple view angles. Structure from motion (SFM) algorithm is used to accurately determine the view angles for each image. The HDRF is calculated for each ground pixel by determining view directions from all of the images for that particular pixel. The pixel intensity values are then processed to reflectance by using a reference panel, which has been measured in laboratory with Finnish Geodetic Institute Field Goniospectrometer (FIGIFIGO). The UAV flight was performed over a test field with different gravel targets. The targets have known HDRF and this allows us to validate the UAV results. Another test was performed over a crop field to display the potential of this method for crop monitoring.
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T. Hakala, E. Honkavaara, L. Markelin, "Hemispherical directional reflectance factor using UAV and a hyperspectral camera, validation and crop field test", Proc. SPIE 9239, Remote Sensing for Agriculture, Ecosystems, and Hydrology XVI, 92390H (29 October 2014); doi: 10.1117/12.2067269; https://doi.org/10.1117/12.2067269
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