></code> can only be applied by
separately considering a harmonic analysis of the “u” and “v”
(e.g. east/west and north/south) velocity components. A more common
approach for such bivariate time series, using the classical fitting
method of least squares, is to combine the horizontal velocity
components into a single complex velocity, e.g.</p>
<p><math display="block" xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>U</mi><mo stretchy="false" form="prefix">(</mo><mi>t</mi><mo stretch