The Vane Room (so-called because the main wind-vane of the Palace stood above it), was on the first floor at the intersection of the Matted Gallery and the Privy Gallery (L&M Companion), which would put it above apartments 20 and 26 on the 1680 Ground Plan of Whitehall. http://www.londonancestor.com/maps/whitehall-pa...
The overlays that highlight 17th century London features are approximate and derived from:
Open location in Google Maps: 51.504061, -0.125001
Chart showing the number of references in each month of the diary’s entries.