Surface Diver uses the hydrophobicity scale introduced by Rose et al.:
To map hydrophobicity onto the surface of a molecule, using the above table, each atom of a certain residue is assigned a similar hydrophobicity index, which is equal to the hydrophobicity of the residue that contains this atom.
Hydrophobicity at a particular point of the surface of the molecule is computed as:
where HBa,aa is the hydrophobicity index of a given atom (residue) and ga is a Gaussian function centered on atom a