Practical methods for aerial image acquisition and reflectance conversion using consumer cameras

Authors: Yang, Chenghai; Fritz, Bradley - Brad; Suh, Charles

Submitted to: European Conference on Precision Agriculture Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 2/20/2023
Publication Date: 6/30/2023
Citation: Yang, C., Fritz, B.K., Suh, C.P. 2023. Practical methods for aerial image acquisition and reflectance conversion using consumer cameras. European Conference on Precision Agriculture Proceedings. pp. 1027-1034. https://doi.org/10.3920/978-90-8686-947-3_129.
DOI: https://doi.org/10.3920/978-90-8686-947-3_129

Interpretive Summary: Consumer-grade cameras have become a viable alternative to more expensive scientific cameras in precision agriculture. This study developed practical methods for determining optimal camera settings and for converting raw digital images to calibrated reflectance data. Two Nikon D7100 and two Nikon D850 cameras with visible and near-infrared sensitivity were mounted on an unmanned and a manned aircraft, respectively, for image acquisition. Camera settings such as exposure time, aperture and ISO were optimized based on flight parameters and image histograms. Regression analysis showed that the exponential model with vertical translation accurately described the relationship between reflectance and raw image data for both visible and near-infrared images. The results from this study provide practical guidance for appropriate configurations of consumer-grade cameras and accurate reflectance conversion for both research and commercial applications in precision agriculture and other applications.

Technical Abstract: Consumer-grade cameras have become a viable alternative to more expensive scientific cameras in precision agriculture. This study developed practical methods for determining optimal camera settings and for converting image digital numbers (DNs) to reflectance. Two Nikon D7100 and two Nikon D850 cameras with visible and near-infrared sensitivity were mounted on an unmanned and a manned aircraft, respectively, for image acquisition. Camera settings such as exposure time, aperture and ISO were optimized based on flight parameters and image histograms. Regression analysis with multiple nonlinear models showed that the exponential model with vertical translation accurately described the relationship between reflectance and DNs based on seven calibration tarps. These results provide practical guidance for appropriate consumer camera configuration and accurate reflectance conversion.