Agricultural drainage tile surveying using an unmanned aircraft vehicle paired with real-time kinematic positioning: A case study

Authors: FREELAND, ROBERT - University Of Tennessee; Allred, Barry; EASH, NEIL - University Of Tennessee; Martinez, Luis; WISHART, DEBONNE - Central State University

Submitted to: Computers and Electronics in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/15/2019
Publication Date: 8/29/2019
Publication URL: https://handle.nal.usda.gov/10113/6837735
Citation: Freeland, R., Allred, B.J., Eash, N., Martinez, L.R., Wishart, D. 2019. Agricultural drainage tile surveying using an unmanned aircraft vehicle paired with real-time kinematic positioning: A case study. Computers and Electronics in Agriculture. 165:104946. https://doi.org/10.1016/j.compag.2019.104946.
DOI: https://doi.org/10.1016/j.compag.2019.104946

Interpretive Summary: Properly functioning subsurface drainage tile systems play essential roles in lowering the water table, making land more cultivable, and determining the quality of surface water in regions. The use of heavy trenching machinery for locating drainage tiles is expensive and could damage existing drainage infrastructure. The ability to locate, excavate, and replace damaged or malfunctioning drainage tiles with accuracy and precision is vital to drainage contractors and farmers. Alternative detection methods are limited by their ability to rapidly cover vast areas of tiled farmland in a short period. This study evaluated an unmanned aircraft system (UAS) integrated with Real Time Kinematic (RTK) Global Positioning System (GPS) technology for its effectiveness in mapping subsurface drainage tiles with precision after photogrammetric processing of the data. The results of the investigation demonstrate standard GPS-based orthorectification lacks geodetic accuracy for the relocation of buried, narrow subsurface drainage tiles in the field. However, an RTK/GPS equipped UAS provides a practical method for precisely and accurately locating buried, narrow tile lines in the field compared to implementing just a standard UAS. In this case study, the UAS integrated RTK technology delivered accurate, low-cost topographical surveys closest to LiDAR accuracy and precision for drainage contractors and farmers. Furthermore, the technology assists in diagnosing drainage effectiveness and detecting functioning legacy (older) drainage tile segments. Besides being cost-effective and time-effective, the use of georeferenced remote sensing technology such as a UAS integrated with RTK/GPS for mapping artificial subsurface drainage tile systems is a significant advancement in precision agriculture.

Technical Abstract: A 2012 agricultural census reported that approximately 218,000 U.S. farms have artificial subsurface drainage tile systems installed on over 19.7 million hectares of cropland. The installation and maintenance of these drainage systems present a significant expense to landowners. Tile probes and heavy machinery excavation are the primary means for locating drain lines. Aerial photography offers promise as a less costly alternative. In the aerial imagery of tiled cropland, ground-surface distortions periodically appear directly atop functioning drain lines. These visible linear segments of drain laterals and mains occur because of variations in surface moisture, temperature, and crop vigor. An unmanned aerial vehicle (UAV) equipped with visible, multispectral (including near infrared (NIR), or thermal infrared (TIR) imaging can detect these distortions at opportune flight times. However, typical UAV-acquired images use standard global positioning systems (GPS) technology, and its low resolution makes it difficult to subsequently pinpoint the exact physical location of the drains within the field. Conventional GPS-referenced photos supply insufficient accuracy and precision for physically locating the narrow drain lines. This study evaluated the effectiveness of unmanned aircraft systems (UASs) that have integrated Real Time Kinematic (RTK) technology for mapping subsurface drainage networks. This surveying technology increases the vertical and horizontal precision and accuracy of aerial surveys as it projects aerial imagery onto a geodetic coordinate system. Results demonstrate that using an RTK-equipped UAS provides a practical method of physically locating buried narrow tile lines precisely in the field. An additional benefit of the UAS integrated RTK technology is the delivery of accurate, low-cost topographical surveys to drainage contractors and farmers. The technique further assists in diagnosing drainage effectiveness and providing correctional accuracy for those GPS-referenced thermal surveys not supporting RTK.