Both maps are enlarged to the same scale to show that Númenor is in fact as big as Beleriand, a fact that is somewhat obscured by the size of the map of Númenor provided in "Unfinished Tales". The colour pattern is that used on modern maps: dark green is lowest, followed by light green through yellow, brown and, ultimately, white.
A few assumptions and interpolations were required, especially to the north of Beleriand. What distinguishes a blank spot named Lothlann from another blank spot named Ard-Galen, so that it deserves a name of its own? Altitude, I assumed: Lothlann is here in fact the bed of an ancient glacier lake that has at some point in early history issued through Maglor's Gap, carving the valley of the Gelion and giving Amon Ereb a distinct tear-like shape, when the floods sculpted it.
Altitudes and vegetation are otherwise interpolated from the texts while the submarine shelfs are based on conjecture only. There are a few more roads than on the official maps because, I assumed, they are needed to connect the places of settlement.
I have never produced LotR maps in that style, because in the same scale that would require eight sheets, with some of them looking rather empty.
I have never produced LotR maps in that style, because in the same scale that would require eight sheets, with some of them looking rather empty.