Estimating Precision of Moving Boat ADCP Discharge Measurement

Hening Huang - Teledyne RD Instruments , 22 August, 2008

The precision of moving boat ADCP discharge measurement is measured in terms of relative expanded uncertainty (REU) and relative maximum residual (RMR). The relation between RMR and REU is established by analyzing field data from 18 sets of moving boat ADCP discharge measurements. The relation reveals that the current RMR criterion of 5% for four transect discharge measurement is equivalent to a REU criterion of 8.7% for the single discharge measurement.

Two models for predicting the moving boat ADCP discharge measurement precision are presented: one for REU and the other for RMR. The models indicate that the parameters affecting ADCP discharge measurement precision fall into three categories: ADCP system performance parameters such as single ping standard deviation and ping rate, channel hydraulic condition parameters such as mean velocity, channel width and depth, and field operational parameters such as boat speed. The models are validated using the field data from the tests in an irrigation canal in Imperial Irrigation District in California, USA. Either the RMR model or the REU model can be used to guide moving boat ADCP measurements for quality assurance and quality control (QA/QC).