Tidal prediction.

johnalison

johnalison

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For me it's just a matter of looking at the tables or getting it from the plotter but I had no idea how complicated it is in reality. I found this video fascinating, at least the first half which deals with tides. We hear about Babbage and his justifiable reputation but I had not heard of Kelvin's essay into this field.
 
johnalison said:
For me it's just a matter of looking at the tables or getting it from the plotter but I had no idea how complicated it is in reality. I found this video fascinating, at least the first half which deals with tides. We hear about Babbage and his justifiable reputation but I had not heard of Kelvin's essay into this field.
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This is fun, too: MONIAC - Wikipedia
 
johnalison said:
For me it's just a matter of looking at the tables or getting it from the plotter but I had no idea how complicated it is in reality. I found this video fascinating, at least the first half which deals with tides. We hear about Babbage and his justifiable reputation but I had not heard of Kelvin's essay into this field.
Click to expand...
It's interesting to read of Fourier analysis being at the outer limits of mathematical inquiry. These days it's routine, and widely used in all sorts of areas - I've used it in several different types of image analysis and signal processing, for example, and analysis of a simple time series like tide-gauge data is not quite trivial, but it's something I'd expect an A-level maths student to do. It happens that there are extremely efficient algorithms for doing Fourier analysis in a digital computer; the Cooley-Tukey algorithm is the basis of them. My pinnacle of achievement in that area was a 3d Fourier transform (and it's inverse) computed using a pipeline of transputers - which rather dates me!
 
AntarcticPilot said:
It's interesting to read of Fourier analysis being at the outer limits of mathematical inquiry. These days it's routine, and widely used in all sorts of areas - I've used it in several different types of image analysis and signal processing, for example, and analysis of a simple time series like tide-gauge data is not quite trivial, but it's something I'd expect an A-level maths student to do. It happens that there are extremely efficient algorithms for doing Fourier analysis in a digital computer; the Cooley-Tukey algorithm is the basis of them. My pinnacle of achievement in that area was a 3d Fourier transform (and it's inverse) computed using a pipeline of transputers - which rather dates me!
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Er - yes.
 
By no way uniquely, my personal computing experience began with log tables at school, slide rules (effectively, mechanical log tables), Brunsviga and Ohdner mechanical, hand operated adding machines, at university, electro-mechanical adding machines in my early working life. Then, it was computers comparable to ENIAC in terms of power, English Electric KDF9 (capable of running four programs simultaneously!) IBM mainframes in the 1970s.

To follow pilot balloons to measure upper level winds, our observers used theodolites and a slide rules with two cursors. One was for elevation angle and one for azimuth. A good observer could follow the balloon and calculate winds at the same time as high as it could be seen, up to 10 or more kilometres. I could do one or the other but never both simultaneously.

Back to Kelvin. Astronomical tidal calculations can be adrift due to wind and pressure as was highlighted by the 1953 east coast tidal surge. Although most dramatic around N Sea coasts, the effects are general. Results of tidal/weather predictions are available at Surge model forecast | National Tidal and Sea Level Facility. These models combine the accurately derived Fourier analysis data with far less precise weather model,oitpiut.
 
davidej said:
In my day, Fourier Analysis was definitely Uni level maths, not school.
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The principle was taught at A-level in the syllabus I did - Joint Matriculation Board of the Northern Universities, 1969 and 1970. It might have been Further Maths rather than Maths, but definitely A-level. As I didn't do maths at University, beyond a first a first-year "Maths for Scientists" course that mostly passed me by, it had to be A-level for me!
 
My maths didn't get further than 'Additional Maths' at O-level, which included some calculus. With four other A-levels to tackle I did no more maths and regretted it somewhat, since my lack of knowledge excludes me from understanding fully a lot of science.
 
I thought I had a reasonable layman's understanding of tides up until I read Jonathon White's book, "Tides".
Beatifully written an an eye-opener as to how little, in reality, I did know.
 
I understand the basics, - the moon and sun pulling the water around, but also understand that it's waaaaaaay more complicated than that, with harmonics and other complexities that go well above my mathematical pay grade, which I have to confess is only a little over minimum wage. I've long forgotten what calculus I knew and most of my trigonometry.
 
AntarcticPilot said:
The principle was taught at A-level in the syllabus I did - Joint Matriculation Board of the Northern Universities, 1969 and 1970. It might have been Further Maths rather than Maths, but definitely A-level. As I didn't do maths at University, beyond a first a first-year "Maths for Scientists" course that mostly passed me by, it had to be A-level for me!
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I don’t remember it being HSC/ A Level in 19t0/51.
 
AntarcticPilot said:
...computed using a pipeline of transputers - which rather dates me!
Click to expand...

I had several of those and their interface chips left over in my late brother's work room. I presume he picked them up when he cleared Salford University's audio engineering dept. after it closed. I can't even begin to fathom what it would take to gather the information needed to implement a system with those, but it didn't stop them going for £400+ on eBay.
 
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