The map shows the recaled frequency calculated for each hectad contoured into bands of 0.1.
We have generally found that this technique produces quite compelling results that fit well with field experience. They do a good job of "filling in the gaps" that result from the rather patchy recording produced by the Recording Scheme.
However, they do not work well for rare species recorded from few hectads, or for outlying hectads from the main distribution. For example, consider the map for Sphaerophoria bankowskae.
At the time of writing, this species is known from only 3 hectads but, due to the neighbourhood weighting method employed by Frascalo, these three records get smeeared over the neighbouhoods of these hectads in a manner related to the neighbourhood weights. This gives the impression of a wider distribution which has no real basis.
Consequently, a bit of caution is needed in relation to the maps for very rare species or when assessing outlying points beyond the main distribution.