  Kevin Lynch proposed a theory of the image of the city identifying five
elements that make the city legible or imageable. The resulting mental map of
the city was conventionally derived through some qualitative processes, relying
on interactions with city residents to ask them to recall city elements from
their minds. This paper proposes a process by which the image of the city can
be quantitatively derived automatically using computer technology and
geospatial databases of the city. This method is substantially based on and
inspired by Christopher Alexander's living structure and Nikos Salingaros'
structural order, as a city with the living structure or structural order tends
to be legible and imageable. With the increasing availability of geographic
information of urban environments at very fine scales or resolutions (for
example, trajectories data about human activities), the proposal or solution
described in this paper is particularly timely and relevant for urban studies
and architectural design.
  Keywords: Mental maps, head/tail division rule, legibility, imageability,
power law, scaling, and hierarchy.
