Measuring a water vortex
like this one presents significant
difficulty, for a number of reasons,
chief amongst which is
obviously the pronounced ripple. The
errors worsen as the
vortex narrows. Nevertheless - with some
good will - we may
see a general conformityto a NULL path curve, and
to a
straight subNULL path curve.
Measurement here is even more problematic, as the ripple
is really a large wobble, which we may see from the severe
displacement of the axis, and there are many lesser ripples,
so we fit to the whole widths - the diameters - which combines
and averages the two profiles, to reduce the impact of all
these spuria.
The result is quite a good fit to path curves—in which the ripples
nevertheless remain quite visible.
