Are you assuming the four corner points are on the surface of the cone?

Yes. They are point on the surface of the cone.

can you assume the xy are in the same unit and are proportional to the z?

I need the x and y in the same units as the grid. Whilst the z values I have are proportional to the units of the grid, the ratio is unknown. However, once the x & y have been determined in any units including the same units as the z components I have, the ratio between them and the grid will become known through pythagoras or other means, so conversion will be trivial.

The most promising stuff I've turned up is trilinear coordinates, but I'm unsure how to apply them, or even if they are applicable.

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In reply to Re^2: OT:Math problem: Grids and conical sections. by BrowserUk
in thread OT:Math problem: Grids and conical sections. by BrowserUk

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