Accuracy Requirements for Surveys

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Accurate surveys are crucial in dam engineering to gather precise and reliable data about the dam and its surrounding areas. As such, the accuracy requirements for these surveys are stringent, as even small errors in measurements can have significant implications for dam design, analysis, and safety. The following are some of the commonly used accuracy requirements for surveys related to dams:

1. Geodetic Control: Geodetic control is the establishment of accurate reference points on the Earth's surface in a survey, as they serve as a basis for all survey measurements and provide a reliable framework for data integration. The accuracy requirement for geodetic control points is typically in the range of a few millimeters to centimeters.

2. Topographic Surveys: Topographic surveys involve mapping the dam site, reservoir area, and the surrounding landscape. These surveys provide information about the existing ground surface, elevations, contours, and features such as roads, structures, and water bodies- features that directly impact the dam. These measurements should be accurate to within a few centimeters to decimeters.

3. Bathymetric Surveys: Bathymetric surveys are conducted to measure the underwater topography of a dam and the depth of the surrounding water. Accurate bathymetric data is essential for determining storage capacity, sedimentation rates, and understanding the hydraulic conditions. Depending on the specific objectives and water depths, the accuracy requirement for bathymetric surveys can range from a few centimeters to decimeters.

4. Construction Surveys: Construction surveys are performed during the construction phase to ensure that the dam is built according to design specifications. The required accuracy requirements for these surveys is typically much higher, ranging from a few millimeters to centimeters.

5. Deformation Monitoring: Continuous monitoring of dam deformations is crucial to assess a dam’s structural behavior and performance over time. Instruments such as GPS, total stations, inclinometers, and settlement gauges, are employed for deformation monitoring. These measurements must be accurate to millimeters or centimeters.

6. Lidar and Remote Sensing: Lidar (Light Detection and Ranging) and remote sensing technologies have been used with increasing frequency in recent years. Lidar systems provide point cloud data, while remote sensing includes satellite imagery and aerial photographs. The accuracy requirement for these surveys often falls from a few centimeters to decimeters.

Overall, accuracy requirements in a survey may vary depending on the specific dam project, regulatory guidelines, and the intended use of the survey data. Accuracy in dam surveys can only be achieved by regular quality control checks, calibration of instruments, and adherence to industry standards and best practices.

Best Practices Resources

Control and Topographic Surveying (EM 1110-1-1005), USACE