Which imaginary resolution do you gain with extrapolating? I think you wrote that there is no physical border because of your floating point space but im not sure. Actually you should reach 3" :p
There's no hard limit. At the moment it's clamped to tile level with 2cm resolution (less than an inch) in horizontal direction. However, while the fractal can be used to generate infinite detail, it will be infinitely similar detail. We would need to provide specialized fractal algorithms for each kind of detail; algorithm for rocks level has to differ from the algorithm generating erosion patterns for mountains or insect level detail.
So where is each data point? I'm assuming they make a grid and have 4 for each 3" square (curved/distorted to make the shape of the earth, at least when the points are applied to the engine).
Input data come indeed as a longitude-latitude aligned grid, but these have to be remapped and compressed before they can be used by the engine.
