Due to economic and environmental considerations, there exists a need for effective, efficient, and nondestructive methods for locating buried agricultural drainage pipes. Previous research indicates that thermal infrared (TIR) imagery obtained with an unmanned aerial vehicle (UAV) has potential for mapping agricultural subsurface drainage systems, thereby warranting further investigation to determine the best time of day to conduct these UAV TIR surveys. Accordingly, a set of sunrise to sunset UAV TIR surveys were carried out at four different farm field sites in Ohio, U.S.A. Late morning through late afternoon UAV TIR surveys were generally found to work well for determining drainage system patterns. During late morning through late afternoon, the apparent radiant temperature of the soil surface over the drain lines was higher than between the drain lines (i.e., emitted TIR radiation from the soil surface over a drain line was greater than between the drain lines). Conversely, near sunrise or sunset, the UAV surveys often showed the apparent radiant temperature of the soil surface over the drain lines to be lower than between the drain lines (i.e., less emitted TIR radiation over the drain lines than between drain lines). Some excellent UAV TIR drainage mapping results were obtained near sunrise/sunset due to TIR drain line responses that were more easily distinguished from those of farm field operations. However, difficulties were occasionally encountered processing this sunrise/sunset TIR imagery, likely due to the impact on image quality from high relative humidity during these times of the day. Consequently, strictly on a consistency of success basis alone, late morning through late afternoon are the best times for locating drainage pipes with UAV TIR surveys; however, in certain cases, UAV TIR surveys at sunrise/sunset can provide exceptional drainage pattern recognition. These results provide valuable guidance for those considering UAV TIR drainage mapping surveys.

由于经济和环境方面的考虑，需要有效、高效和无损的方法来定位埋地农业排水管。先前的研究表明，无人机 (UAV) 获得的热红外 (TIR) 图像具有绘制农业地下排水系统图的潜力，因此需要进一步调查以确定进行这些无人机 TIR 调查的最佳时间。因此，在美国俄亥俄州的四个不同农田地点进行了一组日出到日落 UAV TIR 调查。通常发现上午晚些时候到下午晚些时候 UAV TIR 调查对于确定排水系统模式非常有效。从上午晚些时候到下午晚些时候，排水管线上方土壤表面的表观辐射温度高于排水管线之间的温度（即，从排水管线上方的土壤表面发射的 TIR 辐射高于排水管线之间的辐射温度）。相反，在接近日出或日落时，UAV 勘测通常显示排水管线上方土壤表面的表观辐射温度低于排水管线之间（即，排水管线上发射的 TIR 辐射少于排水管线之间的 TIR 辐射）。由于 TIR 排水线响应更容易与农田作业区分开来，因此在日出/日落附近获得了一些出色的无人机 TIR 排水图结果。然而，在处理此日出/日落 TIR 图像时偶尔会遇到困难，可能是由于一天中这些时间的高相对湿度对图像质量的影响。因此，严格按照成功的一致性，上午晚些时候到下午晚些时候是使用无人机 TIR 勘测定位排水管道的最佳时间；然而，在某些情况下，日出/日落时的无人机 TIR 勘测可以提供出色的排水模式识别。这些结果为那些考虑无人机 TIR 排水测绘调查的人提供了宝贵的指导。