Map of the stained glass windows
The CVMA numbering scheme
The following summary of the Corpus Vitrearum Medii Aevi (CVMA) numbering scheme is by Sarah Brown of the University of York:
The east window (liturgical east) is always number one and then windows are numbered east to west on north and south sides, radiating away from the east window, so that the first window in the north aisle, i.e., at ground-floor level, is n2 (or n, if using Roman numerals) and the first in the south aisle is s2. Upper case S and N are used to indicate windows at clerestory level. For the very small number of British buildings with a glazed triforium, i.e., middle storey, nt2, st2, etc. are used. In other words, the east window is always the unique fixed point and, given a window number, one should be able to locate the window even without a ground plan. In the event that one has an ancillary building attached to a church, it is usual practice to apply the same principles, but to a discretely numbered plan for that structure.
Successive panels within a light are numbered from the bottom upwards, and successive lights within a window are lettered from left to right. Thus, for example, the third panel of the second light of window n4 would be n4 3b.