Illicit sand quarry in riverbeds will become a menace to the worldwide environment and will lead to changes in the river morphology, physical habitation and ecosystem. The excavation of sand in the riverbed is essential because it helps to maintain the river path and avoid flood inundation during the rainy season. But the excess sand removal only creates a negative impact to the surrounding environment. Hence, effective monitoring and scientific audit method are required to identify the illicit sand quarry. The assessment of excess sand excavated area and volume is a major task for the Economic and Revenue Sector Audit (E&RSA) officials. Also, the volume calculation of sand quarry is a tedious and time-consuming process when using a traditional survey instrument like total station. Integration of unmanned aerial vehicle (UAV) remote sensing (R/S) technology with modern survey instrument like differential global positioning system (DGPS) will reduce the survey time, cost and manpower. In this study, the UAV-based aerial survey and DGPS observation were done in Economic and Revenue Sector Audit (E&RSA), a specified sand quarry site. The acquired UAV aerial images and DGPS points were subsequently used to generate orthomosaic map, digital terrain model (DTM), digital surface model (DSM) and 3D mesh. The UAV-derived outputs have been compared with lease map and revenue records. All the findings related to violations in approved lease boundary, volume and depth were reported to E&RSA to estimate the revenue loss to the government.

中文翻译：

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无人机遥感技术在采砂场体积审计和环境影响评估中的应用：以印度泰米尔纳德邦库达洛尔区 Neyvasal 采砂场为例

河床中的非法采砂将成为对全球环境的威胁，并将导致河流形态、自然栖息地和生态系统的变化。在河床挖沙是必不可少的，因为它有助于维护河道，避免雨季洪水淹没。但多余的沙子去除只会对周围环境造成负面影响。因此，需要有效的监测和科学的审计方法来识别非法采石场。评估多余的沙子开挖面积和体积是经济和收入部门审计 (E&RSA) 官员的一项主要任务。此外，使用全站仪等传统测量仪器时，采石场的体积计算是一个繁琐且耗时的过程。将无人机 (UAV) 遥感 (R/S) 技术与差分全球定位系统 (DGPS) 等现代测量仪器相结合，将减少测量时间、成本和人力。在本研究中，基于无人机的航测和 DGPS 观测是在指定采砂场的经济和收入部门审计 (E&RSA) 中完成的。随后使用获得的无人机航拍图像和 DGPS 点生成正射镶嵌图、数字地形模型 (DTM)、数字表面模型 (DSM) 和 3D 网格。无人机衍生的输出已与租赁地图和收入记录进行了比较。所有与批准的租赁边界、体积和深度违规相关的调查结果都报告给了 E&RSA，以估计政府的收入损失。