High-Resolution Mapping of Tile Drainage in Agricultural Fields Using Unmanned Aerial System (UAS)-Based Radiometric Thermal and Optical Sensors

Abstract

With the growing concerns of water quality related to tile drainage in agricultural lands, developing an efficient and cost-effective method of mapping tile drainage is essential. This research aimed to establish mapping of tile drainage systems in agricultural fields using optical and radiometric thermal sensors mounted on Unmanned Aerial System (UAS). The overarching hypothesis is that in a tile-drained land, spatial distribution of soil water content is affected by tile lines, therefore, contrasting soil temperature signals exist between areas along the tile lines and between the tile lines. Designated flights were conducted to assess the effectiveness of the UAS under various conditions such as rainfall, crop cover, crop maturity and time of the day. Image correction, mosaicking, image enhancements and map production were conducted using Agisoft and ENVI image analysis software. The results showed intermediate growth stage of soybean plants and rainfall helped delineating tile lines. In-situ soil temperature measurements revealed appropriate time of the day (14:00 to 18:00 h) for thermal image detection of the tile lines. The role of soil moisture and plant cover is not resolved, thus, further refinement of the approach considering these factors is necessary to develop efficient mapping techniques of tile drainage using UAS thermal and optical sensors.

Mapping subsurface tile lines on a research farm using aerial photography, paper maps, and expert knowledge

“…(2020) found that a light rain of 13 mm 5 days prior to image acquisition was the reason for the poor detection of tile lines on thermal images. A more recent study (Tilahun & Syoum, 2021), however, found that a thermal image collected in the afternoon of a day on which 16.8 mm of rain fell in the morning showed better contrast than an image collected after 2 days of 2.3 mm rain. Additionally, Allred et al.…”

“…Indiana, with approximately 50% artificially drained cropland, is the highest in the nation (Pavelis, 1987). Accurate maps of preexisting tile lines are not only important for agronomic and environmental research but also for the maintenance and repair of current drainage systems, and for reference during the installation of new tile lines in previously tiled fields (Becker et al., 2021; Gökkaya et al., 2017; Tilahun & Syoum, 2021). In many cases, however, the locations of existing tile lines are not known exactly because maps of their locations were not made, the original maps have been lost, or the tile lines were inaccurately georeferenced.…”

“…Soil moisture, soil organic matter, soil texture, crop residue, and tillage practices, however, also affect the reflectance and, therefore, the accuracy of automated tile mapping using aerial imagery (Andrade, 2013; Freeland et al., 2019; Naz & Bowling, 2008; Naz et al., 2009). Recent studies utilized UAVs (unmanned aerial vehicles) equipped with various cameras (i.e., visible, thermal, and multispectral) for mapping subsurface tile lines (Allred et al., 2021, 2020; Becker et al., 2021; Freeland et al., 2019; Kratt et al., 2020; Tilahun & Syoum, 2021). The efficiency and success of UAV technology in mapping subsurface tile lines are impacted by the existence of linear features due to the farm operations, type of camera used, and variation in spatial and temporal properties such as water content, soil type, and vegetation (Allred et al., 2020; Naz et al., 2009).…”