RIV (Relative Identity Value): Measures the percentage of pairwise (qualitative) matchings of the elements (types, taxates) of two measuring point profiles.
Basic assumption: equal weighting of all compared linguistic types ("taxates").
WIV (Weighted Identity Value): Measures the percentage of pairwise (qualitative) matchings of the elements (types, taxates) of two measuring point profiles.
Basic assumption: variable weighting of all compared linguistic types ("taxates") as a function of the size of the respective geographic areas. The pairwise match of taxates with small areas is considered to be numerically more important in the final result than the pairwise matchings of taxates with larger areas, which from a geolinguistic point of view could be regarded as "banal" or "less significant". In the formula of the WIV - more precisely: WIV(x) - there is a freely selectable divisor x (between 1 [= maximum weighting] and infinite [= minimum weighting]) to control the weighting. Here one can see results based on maximal weighting (ponderation).
Note on isogloss and beam maps: The cartographic message of the two types of visualization is complementary: while on isogloss maps the different polygon sides visualize distances (d), on beam maps the triangle sides are used to visualize similarities (s). The relationship between s and d is governed by the following formula: s + d = 1 (or 100). The result is: RIV + RDV (Relative Distance Value) = 100. The same applies to the WIV.