2.2. Definition of design and structural rules for the development of SIENA
The findings of the statistical description of the sample cities were translated
into design and structural rules to inform the development of the SIENA core
structure. Table 2 lists the main findings of the statistical analysis and the deduced
design and structural rules.
The main findings of the statistical description were: a) coastal cities and
inland cities significantly differ in their structure for some urban components, but
inland cities are very comparable in their structure; b) the spatial distribution of
urban components is highly depended on the distribution of the other urban
components, a trend found for all cities analysed; c) the terrain is the structural
feature that most strongly influences the spatial distribution of the other urban
components; and d) the spatial distribution of the minor road network, the land
cover and the population density indicate very intricate patterns with the other
urban components that vary also with distance from the city centre. All results of
the statistical analysis for the different urban components are presented in the
Supplement material.
On this basis, SIENA was built as an urban area situated inland with focus on i)
the relationship between the urban components, ii) the relationship with the terrain
and iii) the representation of centrality (see Table 2).
The resolution of SIENA had to be the highest possible spatial resolution to allow
for the detection of fine spatial patterns in the urban environment and at the same
time be computational feasible. Sensitivity analysis carried out for the city of
Leicester revealed that a 25 25 m resolution fulfilled these requirements (for
details of sensitivity analysis see Supplement material). This is also the spatial resolution
of the land cover data and increasing the resolution would introduce false
precision and distort interpretation of any simulated results.
2.3. The construction of SIENA
Different approaches were used to model the different urban components to
reflect the requirements set in the design and structure rules and the nature of the
data (see Fig. 3). Urban components were modelled either as line features (e.g. main
roads) or as a grid (e.g. land cover).