Velocity Angle - Xylem SonTek FlowTracker2 User Manual

i). If the number of spikes is a greater percentage of the total number of points
than specified by the Spike Threshold, a warning is given.
• This may indicate interference from an underwater obstacle, a highly
• At the first alert, repeat the measurement (perhaps after moving probe
• If the problem persists, evaluate the measurement environment – a large
ii). The Spike Threshold is checked with the completion of a point velocity
measurement and measurement section (see
• User is notified of any stations that exceed the above criteria.
• If desired, user can go back and delete suspect stations and repeat the
g) The Velocity Spike Filter is checked at the end of each point velocity
measurement and if
Threshold, then give the High % Spikes warning.
h) The velocity spike filter check is re-run (Discharge mode and General mode
measurement) to ensure the warnings are set with the most current data.
f) This criterion can be adjusted or disabled under
6.1.5

Velocity Angle

The Velocity Angle quality control parameter is applied to each point velocity
measurement in Discharge mode.
a) For an ideal discharge measurement site, flow should be perpendicular to the tag
line used to define the cross section.
b) A good measurement site will typically show some flow variations, but with all
angles less than about 20°.
c) The ability of the FlowTracker2 to measure the 2D flow eliminates the need to
estimate the flow direction with each measurement, as is required for most 1D
current meters. This reduces a potential source for error in velocity
measurements.
Velocity d) Velocity angle is defined as the direction of flow relative to the X direction, and is
Angle calculated as atan(Vy/Vx).
Method
i). The FlowTracker's X-axis is always held perpendicular to the tag line.
FlowTracker2 User's Manual (January 2019)
turbulent environment, or highly aerated water.
location).
number of spikes may be unavoidable, but may not overly impact the
quality of velocity data.
measurements.
the number of velocity spikes is larger than allowed by the Spike
SonTek – a Xylem brand
Timing of Warning
Quality Control
91
Messages).
Settings.