The similarity maps show the spatial stratification of the quantitative similarities that result - always according to the preselected similarity measure (RIV, WIV etc.) - between a preselected atlas point ("reference point") and the remaining N-1 measuring points of the respective atlas grid. The reference point is selected by clicking (or activating) the polygon in question, whose surface remains white subsequently. The remaining N-1 polygons are colored according to the specifications of two interval algorithms (MINMWMAX and MEDMW) and using 2, 4, 6, 8, 10 or 12 color levels taken from the solar spectrum.
Note that among the mentioned N (= 641) inquiry points of the ALF there are 638 original points and another three artificial points which we had introduced for comparison purposes: 999 standard French (at the place of Paris), 998 standard Italian (at the south-south-east corner of France), 997 standard Catalan (at the southern tip of France in the department of Pyrénées Orientales).
Note that the mentioned N (= 382) measuring points do not correspond to the entire network of the AIS with its 407 measuring points. Due to missing data only 380 measuring points could be considered. However, two artificial points were added to these, mainly for comparison purposes: 999 standard Italian (at the place of Florence), and 998 standard French (at the northern edge of the Aosta valley).
Note that among the mentioned N (= 313) inquiry points of the SED there are 312 original points and an additional artificial point which was introduced by us for comparison purposes: 999 standard English. It was inserted into the SED network at the place of London.