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Research Project: Aerial Application Technology for Sustainable Crop Production

Location: Aerial Application Technology Research

Title: A case study of comparing radiometrically calibrated reflectance of an image mosaic from unmanned aerial system with that of a single image from manned aircraft over a same area

Author
item SHI, YEYIN - University Of Nebraska
item THOMASSON, JOHN - Texas A&M University
item Yang, Chenghai
item COPE, DALE - Texas A&M University
item SIM, CHAO - Texas A&M University

Submitted to: Proceedings of SPIE
Publication Type: Proceedings
Publication Acceptance Date: 7/10/2017
Publication Date: 7/17/2017
Citation: Shi, Y., Thomasson, J., Yang, C., Cope, D., Sim, C. 2017. A case study of comparing radiometrically calibrated reflectance of an image mosaic from unmanned aerial system with that of a single image from manned aircraft over a same area. Proceedings of SPIE. Vol. 10218, 102180B-1.

Interpretive Summary: One of the major differences between conventional manned aircraft and low-altitude unmanned aerial system (UAS)-based remote sensing platforms is that the latter has much smaller image footprint. To cover the same area on the ground, it requires the UAS-based platform to take many highly-overlapped images over a long time period to produce a good mosaic, while the manned aircraft platform only needs one or a few image shots. In this study, comparisons of the difference in calibrated image reflectance values between the UAS mosaicked image and the manned aircraft-based single image for an agricultural field were made. Correlation analysis showed that the image values between the two images were significantly correlated, though discrepancies were found in average reflectance values between the two images. The results of this study should serve as a starting point for a series of follow-up studies to understand the environmental influence on UAS data and investigate the solutions to minimize such influence to ensure data quality.

Technical Abstract: Although conventional high-altitude airborne remote sensing and low-altitude unmanned aerial system (UAS) based remote sensing share many commonalities, one of the major differences between the two remote sensing platforms is that the latter has much smaller image footprint. To cover the same area on the ground, it requires the low-altitude UAS-based platform to take many highly-overlapped images to produce a good mosaic, instead of just one or a few image shots as by the high-altitude aerial platform. Such a UAS flight usually takes 10 to 30 minutes or even longer to complete; environmental lighting change during this time span cannot be ignored especially when spectral variations of various parts of a field are of interests. In this case study, we compared the visible reflectance of two aerial images – one generated from a mosaicked UAS image and the other from a single image taken by a manned aircraft – over the same agricultural field to quantitatively evaluate the spectral variations caused by the two different data acquisition strategies. Specifically, we developed our customized ground calibration points (GCPs) and an associated radiometric calibration method for UAS data processing based on camera’s sensitivity characteristics and developed a basic comparison method for radiometrically calibrated data from the two aerial platforms based on regions of interests. We see this study as a starting point for a series of following studies to understand the environmental influence on UAS data and investigate the solutions to minimize such influence to ensure data quality.