Renumeralisation is a method to construct new maps by modifying well known true or untrue projections.
If the image co-ordinates of the initial map projection are given by
x = x (u,v) and y = y (u,v) , (1)
so the renumeralisation (transformation) takes place by suitable functions
u = u (s,t) and v = v (s,t) , (2)
which (inserted in the image co-ordinates above (1)) will deliver the new projection co-ordinates.
If the so constructed map projection is supposed to have certain »differential-geometrical characteristics« - i.g. area-fidelity or conformality -, these characteristics cause certain »side conditions« for the functions (2).