Xylem SonTek FlowTracker2 - Discharge Uncertainty Calculation

SonTek – a Xylem brand
FlowTracker2 User’s Manual (January 2019)
79
Station Type
Velocity Method
Correction Factor
0.2 / 0.8
1
0.2 / 0.6 / 0.8
1
Enter Velocity
1
Ice
None
User defined
0.5
0.88
0.6
0.92
0.2 / 0.8
1
0.2 / 0.6 / 0.8
1
Enter Velocity
1
c) The CF can consist of any value between -1.00 and 1.00, except 0.0.
d) The CF can be entered for any station and the mean station velocity will be
multiplied by the CF.
Discharge Uncertainty Calculation 5.1.4
Discharge Uncertainty Calculation is performed on every discharge measurement to
determine the overall measurement uncertainty.
a) The uncertainty calculation methods implemented in FlowTracker2 is based on
the Interpolated Variance Estimator (IVE) and ISO methods,
i). The Interpolated Variance Estimator (IVE) uncertainty calculation method
uses a method developed by researchers at the U.S. Geological Survey. The
IVE uncertainty calculation is the default method as it provides the most
reliable indicator of measurement quality,
ii). The ISO method is based on the international standard. It provides users with
the results of a published, standard technique; however, in some cases this
calculation may not provide a reliable indicator of data quality.
The uncertainty analysis implemented for determining the overall discharge uncertainty
are based on the following literature,
• ISO 748 – 2007, Hydrometry - Measurement of liquid flow in open channels using
current meters or floats,
• Cohn, T., Kiang, J., and Mason, R., Jr. (2013). ”Estimating Discharge Measurement
Uncertainty Using the Interpolated Variance.
b) The application of uncertainty calculation methods to discharge calculation
methods are defined,
i). The uncertainty calculation methods implemented are only applicable to the
“Mid-Section” and “Mean-Section” discharge calculation methods.
ii). The Japanese method does not incorporate discharge uncertainty calculations
and a method “None” is assigned.