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

Accurate maps of subsurface tile drainage lines are needed for agronomic and environmental research studies and the maintenance of current tile drainage systems. In this study, tile lines at the Purdue University Agronomy Center for Research and Education near West Lafayette, Indiana were located using a combination of visual aerial photo interpretation, expert knowledge, and paper construction drawings. The mapping accuracy was assessed at 27 locations where tile lines were located physically using a tile probe. Tile lines were correctly predicted 89% of the time with an average spatial accuracy of ±1.23 m of the true tile locations. This approach was better than a previous tile line location map prepared using an automated remote sensing method, which had an average spatial accuracy of ±2.12 m. Core Ideas Tile lines were located based on visual aerial photo interpretation, paper maps, and expert knowledge. Photo interpretation was a useful method to map unknown tile lines and provided better results than remote sensing. Accurate location of tile lines is vital for agronomic and environmental research studies.