Data Visualisation & A Question

2.0] Data Visualisation:

Data visualised includes resources such as global topography/bathymetry (eg. GEBCOETOPO1); volumetric ocean models; sea ice data; krill observation datasets; deep sea ocean trawl video; CTD profiles (conductivity/temperature/depth); sub-surface buoys; sonar information; long-range remote sensing data; voyage track data; marine life track data; electron microscopy data.

The sheer amount of data available via Australian and international scientific programmes is overwhelming: it is a truly remarkable intellectual and observational achievement of humanity. When you begin to dig deeper into available resources you begin to realise what a credit it is to the public nature of science that thousands and thousand of individuals all over the world have given of their time, not only professionally, but personally as well, to share their hard-won and vastly complex knowledge about the world that we live in. This is also a function of the time we live in, when information can be made globally accessible via the internet and when download speeds enable the transaction of huge datasets, many of which are measured in terabytes and, in the near future, in petabytes and exabytes. Needless to say very fast networked supercomputers with large amounts of RAM and high-end GPUs are also crucial to this developing area.

In this project I can barely scratch the surface of what is possible – so this presents an initial problem – where to start? Having given this substantial thought I decided upon a deceptively simple question:

3.0] “What is the shape of the sea?”

It has become apparent to me that we have a deeply terrestrial view of the world – ordered by a whole series of anthropocentric conventions – and that in looking at and attempting to understand the sea – much of this apparatus must be discarded. It is similar to the feeling of looking at a world-map upside down: the familiar landmarks, the topology, are estranged and made unfamiliar – we lose our bearings. The paradox then, in order to  “find” the sea as a globally encompassing body of water, is precisely to explore this ‘seeing the aspect‘ as an advantage.

When we look at global topographic and bathymetric models of the Earth, what we see is the surface of Earth – the rock surface, the geology: not the fluid world. The dataset is constructed from millions of point readings of the elevation of that surface in relation to ‘nominal sea level’ – itself determined in relation to the Earth geoid(WGS84 and other models) that mathematically describe the complex shape of our planet. This is a very complex area that I can only gloss here – as a non-expert – so I encourage you to read the links for clarification.

Remarkably, in my research into this question, I have found no images at all of what the sea would look like if we simply saw it as a self-contained volume – the largest biosphere on the planet, in which most of the world’s life exists, in an entirely different volumetric and physical way to which we perceive and interact with tjavascript:;he world. So I posed this question to Paul Bourke at the WASP: how would it be possible to construct a volume representation of the global ocean? Isn’t it a matter of ‘simply’ subtracting the GEBCO topography/bathymetry from the WGS84 geoid? The answer is, principally, yes, but as Paul figured out, the solution is more complex than it seems – and involved writing some software that could accurately calculate the intersection of “mean sea level” with global coastlines as well as retaining the bathymetric structure of the ocean floor – at many resolutions. This has led to the development of a new dataset derived from GEBCO that creates an accurate high-resolution polygonal mesh of the global ocean. In itself this is not, strictly speaking, volumetric (we will cover this later on in detail), as the the model derived is a polygonal closed solid that represents the surficial shape of the ocean – however, it is a remarkable object and gives us a unique view of the world’s global oceans.

See Paul’s notes upon deriving the model:

Important note: the depth exaggeration is a factor of 200 – the ocean, like the atmosphere, is a thin veil across the surface of the earth, despite its prodigious depths. If it was not exaggerated we would barely see it in this model.

Here’s a short first-attempt quicktime movie visualising this polygonal volume, as if the global ocean was frozen at a point in time and cast in blue glass:

This link will take to to my website where you can view the movie:

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