The similarity maps show the spatial stratification of the quantitative similarities that result - always according to the preselected similarity measure (RIV, WIV[1] 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 (= 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.