tide prediction – especially since the vessel
was going to be at sea for two weeks – but
fortunately I was able to persuade the skipper to drop me off as we passed the outer
pier in Scarborough harbour.
The business started to expand in the early
2000s, allowing me to hire a business administrator and a programmer with an MSc in
astronomy. In 2003 we decided to concentrate on the specialist area of harmonic tidal
analysis. This is like a first cousin of Fourier
analysis, and it enables you to work out the
transfer function between the tidal potential
and the instantaneous tidal height. It also
provides highly accurate figures for mean
sea level. So far, our systems for tidal harmonic analysis have been used in more than
30 hydrographic offices for tidal prediction
and by numerous hydrographic surveyors to
determine sea level. Given the threat of climate change and its associated predicted rise
in sea level, systems like ours are a useful tool
for examining recent trends. The good news
is that even with our advanced analysis software, any rise in sea level is almost entirely
masked by noise on the tide gauge data from
storms and surges – so far.
Real-world physics
In this industry, it is not unusual to find physicists (many with their own businesses) working amongst hydrographers, mariners and
oceanographers. Hydrographic topics like
map projections, navigation and data analysis figure high on the list of requirements,
and all use very similar mathematical skills
to those required in physics.
For example, the physics problems associated with tidal prediction are actually quite
similar to those of infrared spectroscopy.
Both techniques deal with issues like resolution, line width and modulation – it is just
a matter of changing the frequency band
from infrared spectral lines at about 1013 Hz
to tidal “spectral lines”, or constituents, of
about 10–7 Hz. The strongest tidal constituent
comes from the semidiurnal (twice-daily)
tide and has a frequency of 2 × 10–5 Hz. In
long-duration datasets of tidal height, in
contrast, significant tidal components can be
resolved down to events that occur about
once every 18 years, or 10–9 Hz – a frequency
in line with theoretical models based on the
known orbital parameters of the Sun–Moon–
Earth system.
Just as in the field of non-linear optics, non-linear effects generate additional frequency
components, producing for example the phenomenon of standing tides that are found on
parts of the UK’s south coast. In this field,
at least, Reverend Brother Egbert’s phrase
about all physics being oscillatory is pretty
much spot-on.
On a day-to-day basis, my job as head of a
small-marine software firm involves some
programming and some sales work, as well
as speaking to mariners, port hydrographers
and representatives from the oil and fishing
industries. Recently I have also presented a
few papers at hydrographic and oceanography conferences, but I am not obliged to
churn out publications to meet some bureaucratic university target, and am unfettered
by internal politics. Instead, I have the freedom to use the skills I gained as a physicist to
benefit clients in the wider world, where I
have found there is a great need for the practical application of physics and which can be
outstandingly rewarding.
Stephen Taylor is managing director of Geomatix Ltd,
e-mail set@geomatix.net, Web www.geomatix.net
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