. Analysis of the emission variability maps in the two Italian
domains
Emission variability maps are here discussed as a whole,
without looking in details around measurement sites. To achieve
the most suitable maps for the interpretation of emission
variability, the “natural breaks” classification of mapped values
(Jenks, 1967), available in GIS environment, was applied. The
analysis of the frequency histograms of the raster datasets, highlighted
non-uniform distributions of emission variability values,
with high frequency of low values, degrading rapidly at higher
values of the plot. Therefore, the natural breaks classification was
chosen in order to use more classes where there is higher occurrence
of values, for better representing the emission variability.
Indeed, the natural breaks classification method is a data clustering
method designed to determine the best arrangement of values into
different classes. Break points are identified by picking the class
breaks that best group similar values and maximize the differences
between classes. The features are divided into classes whose
boundaries are set where there are relatively big jumps in the data
values. The method seeks to reduce the variance within classes and
maximize the variance between classes.