Overall results and key findings on the use of UAV visible-color, multispectral, and thermal infrared imagery to map agricultural drainage pipes

Authors: Allred, Barry; Martinez, Luis; FESSEHAZION, MELAKE - Volunteer; ROUSE, GREG - Ross County Soil & Water Conservation District; WILLIAMSON, TANJA - Us Geological Survey (USGS); WISHART, DEBONNE - Central State University; KOGANTI, TRIVEN - Aarhus University; FREELAND, ROBERT - University Of Tennessee; EASH, NEAL - University Of Tennessee; BATSCHELET, ADAM - Green Aerotech Usa; FEATHERINGILL, ROBERT - Farmer

Submitted to: Agricultural Water Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/16/2020
Publication Date: 2/1/2020
Publication URL: https://handle.nal.usda.gov/10113/6818609
Citation: Allred, B.J., Martinez, L.R., Fessehazion, M., Rouse, G., Williamson, T., Wishart, D., Koganti, T., Freeland, R., Eash, N., Batschelet, A., Featheringill, R. 2020. Overall results and key findings on the use of UAV visible-color, multispectral, and thermal infrared imagery to map agricultural drainage pipes. Agricultural Water Management. 232:106036. https://doi.org/10.1016/j.agwat.2020.106036.
DOI: https://doi.org/10.1016/j.agwat.2020.106036

Interpretive Summary: There are strong economic and environmental motivations for finding effective, efficient, and non-destructive methods to map agricultural subsurface drainage systems. The use of unmanned aerial vehicles (UAVs) with visible true color (VIS-TC), multispectral (MS) and thermal infrared (TIR) cameras may provide the solution to the drainage mapping problem. This technology was tested at 29 different field sites in the Midwest U.S.A (states of Indiana, Iowa, Michigan, and Ohio). The UAV VIS-TC imagery detected at least some drain lines at 52% of the sites (15 out of 29), MS imagery detected drain lines at 52% of the sites (15 out of 29), and TIR imagery detected drain lines at 69% of the sites (20 out of 29). Three key findings regarding UAV drainage pipe mapping were extracted from the overall results. (1) Although TIR generally worked best, there were sites where VIS-TC and/or MS were more effective than TIR for mapping subsurface drainage systems. Consequently, to ensure the greatest chance for successfully determining drainage pipe patterns in a field, UAV surveys need to be carried out with all three types of cameras, VIS-TC, MS, and TIR. (2) The timing of UAV surveys relative to rainfall can be very important in regard to drainage pipe detection. However, the recommendation to only conduct UAV surveys outside the growing season and two to three days after a large rainfall event, while possibly ideal, may be far too restrictive. (3) Where the origin of linear features present in UAV imagery is initially unclear, knowledge of subsurface drainage system installation and farm field operations can be utilized to distinguish linear features representing drain lines versus the linear features due to harvest, tillage, fertilizer, and/or planting efforts. Aside from these three key findings, even if this technology is not successful at a particular site for finding drainage pipes, it is still useful for the topographic information it can provide, which in and of itself is valuable to drainage contractors installing or retrofitting subsurface drainage systems or for gaining insight on surface runoff attributes. Future work will focus on five to six Ohio or Indiana farm field sites, each of which will be visited at least six to eight times over a two year period for subsurface drainage mapping with UAV VIS-TC, MS, and TIR cameras. With this approach, the range of site conditions (soil type, time of year, wetness/dryness, and surface characteristics) under which a particular type of imagery (VIS-TC, MS, or TIR) is effective at mapping drain lines will be determined. These results will then be employed to develop specific guidelines on the use of UAV VIS-TC, MS, and TIR imagery to map agricultural subsurface drainage systems.

Technical Abstract: Effective and efficient methods are needed to map agricultural subsurface drainage systems. Visible true color (VIS-TC), multispectral (MS), and thermal infrared (TIR) imagery obtained by unmanned aerial vehicles (UAVs) may provide a means for determining drainage pipe locations. Aerial surveys using a UAV with VIS-TC, MS, and TIR cameras were conducted at 29 agricultural field sites in the Midwest U.S.A. to evaluate the potential of this technology for mapping buried drainage pipes. Regarding overall results, VIS-TC imagery detected at least some drain lines at 52% of the sites (15 out of 29), MS imagery detected drain lines at 52% of the sites (15 out of 29), and TIR imagery detected drain lines at 69% of the sites (20 out of 29). Three key findings, listed as follows and emphasized in this article by site examples, can be extracted from the overall results. (1) Although TIR generally worked best, there were sites where VIS-TC and/or MS were more effective than TIR for mapping subsurface drainage systems. Consequently, to ensure the greatest chance for successfully determining drainage pipe patterns in a field, UAV surveys need to be carried out with all three types of cameras, VIS-TC, MS, and TIR. (2) Timing of UAV surveys relative to recent rainfall can sometimes have an important impact on drainage pipe detection results. (3) Linear features representing drain lines and farm field operations can be confused with one another and are oftentimes both depicted on site aerial imagery. Knowledge of subsurface drainage system installation and farm field operations can be employed to distinguish linear features representing drain lines from those representing farm field operations. The overall results and extracted key findings from this study clearly indicate that VIS-TC, MS, and TIR imagery obtained with UAVs have significant potential for use in mapping agricultural drainage pipe systems.