I’ve done the math on how much storage would be required to store the entire planet, in 3D, in one centimetre cubes. Reaching 1km in height, to allow for the tallest buildings and basements, and giving each pixel 64 bits to describe it, would equal a massive amount of data.

All of Google’s data centres combined currently hold 10 million terabytes. MapMerge would require 400 million times more than that, if every pixel was to hold unique information.

Even if only urban areas were mapped (1% of the planet), and only to a height of 5 metres, we would still need 6500 times Google’s current storage capacity.

So the answer will be something akin to level mapping in 3D video games.