GPR and UAV mapping of agricultural subsurface drainage systems: A research overview

Authors: Allred, Barry

Submitted to: Fast Times: News for the Near Surface Geophysical Sciences
Publication Type: Trade Journal
Publication Acceptance Date: 9/18/2020
Publication Date: 9/30/2020
Citation: Allred, B.J. 2020. GPR and UAV mapping of agricultural subsurface drainage systems: A research overview. Fast Times: News for the Near Surface Geophysical Sciences. 24(3).

Interpretive Summary:

Technical Abstract: This article provides an overview of research conducted on the use of ground penetrating radar (GPR) and an unmanned aerial vehicle (UAV) for mapping buried drainage pipe networks in farm fields. Due to economic and environmental considerations, there exists an important need for effective, efficient, and nondestructive methods for locating buried agricultural drainage pipes. Regardless of whether the need is economic or environmental, finding drain lines with a hand-held tile probe is time-consuming, extremely tedious, and if not careful, can damage buried pipes. Using heavy trenching equipment is generally effective, but always causes considerable pipe damage requiring costly repairs. Several near surface geophysical methods (electromagnetic induction, ground penetrating radar, magnetometry, and resistivity) were tested for for subsurface drainage mapping, but success was obtained only with ground penetrating radar (GPR). However, even with integrated GPR and RTK/GNSS equipment mounted on an all-terrain vehicle, completing more than 15 ha (40 acres) of a farm field drainage mapping survey in a single day is difficult, so for larger areas, a different method is needed. Unmanned aerial vehicles (UAVs) with visible-color (VIS-C), multispectral (MS), and/or thermal infrared (TIR) cameras can provide a solution for mapping agricultural subsurface drainage systems in large farm fields. Aerial surveys using a UAV with VIS-C, MS, and TIR cameras were conducted at 29 agricultural field sites in the Midwest U.S to compare these technologies for drainage mapping. Overall results from this study show VIS-C imagery detected at least some drain lines at 48% of the sites (14 out of 29), MS imagery detected drain lines at 59% of the sites (17 out of 29), and TIR imagery detected drain lines at 69% of the sites (20 out of 29). Consequently, both GPR and UAV surveys exhibit promise for mapping agricultural subsurface drainage systems. Of the two, UAV surveys are far more efficient and provide capability for mapping drainage pipe networks in larger farm fields (>15 ha). However, the use of GPR can still be valuable for ground truth of suspected drain line locations depicted by UAV imagery.