This animation is actually a couple of different approaches combined to give a very brief introduction to the operation of robotic gliders, before showing an example glider mission between Scotland and Iceland.   I’ve wanted to depict a more realistic glider flight for a while; the problem being that in order to show the nature of water structure you have to exaggerate the bathymetry by ~50 times.  This has the effect of compressing the glider’s horizontal motion to a series of very tight zigzags.

Here, I created a few pseudo profiles using real observations but with artificially set waypoints, which allowed a more realistic flight profile to be shown.

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Simulation of glider flight in Paraview

Accordingly, a glider simulation needs a glider.  Unfortunately I haven’t become sufficiently advanced in Paraview to import mesh shapes, so the glider shown here is a carefully constructed mish-mash of basic shapes available in Paraview: cones, cylinders and cuboids.  Its trajectory is supplied in vector form along with the data from a Matlab script, again adjusted for the exaggerated z axis.  The effect works quite well though there’s something funny going on with the shadow rendering on the cylinder – its light source is coming from somewhere different altogether!  A translucent textured sea surface was added to give a sense of depth.

For the true glider dataset, a spherical coordinate system was employed as a Scotland-Iceland transect covers a good deal of ground, and the taper towards the North pole is substantial.  The only way i’ve found to reliably do this is pre-processing in Matlab.  With some head-scatching and basic trigonometry, it’s possible to translate (lon,lat,depth) data into positions on a sphere in (x,y,z) space.  The convention I used was to set the Earth’s centre at (0,0,0), north in the z direction with a nominal diameter of 1.  Anything greater than 1 is above the sea surface, anything less than 1 is below.

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Scotland-Iceland glider transect set on exaggerated spherical bathymetry

The bathymetry and consequently the depth space occupied by the glider is exaggerated by 50.  Everything is normalised to the Earth’s new diameter of 1.  There is a very faint textured sphere representing the ‘sea surface’ in this animation too, but if I increase the opacity above ‘barely visible’ it distracts from the glider track.

 

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