Identification and correction of water velocity measurement errors associated with ultrasonic Doppler flow monitoring
Ultrasonic Doppler flow monitoring (UDFM) is used to measure water flow in pipes and channels. However, a lack of scattering particles and signal noise can cause velocity errors, particularly for smaller discharges and surface water (‘clean’) flows. A postprocessing methodology is presented that identifies and corrects these errors, maximising the value of existing data. Test criteria are used to identify errors. The error correction procedure defines depth–velocity relationships from cleaned ‘training data’ representing the range of flow conditions (including backed up) and uses these relationships to replace erroneous velocities automatically. UDFM velocity errors have been successfully identified and corrected in example applications. Routine use allows early identification of changes in instrument or site behaviour. The methodology is practical, consistent and updateable. This is a significant advancement over previous methods for correcting velocity errors, improving the applicability of UDFM.