Geoscience Reference
In-Depth Information
- The questions about
the dynamics of spatial entities
themselves: these entities
then have a “meaning”, and a rather “object” oriented approach is then involved.
The analysis will focus on the evolution of these objects: the point will be to look for
similarities between these evolutions, as well as identifying types, and assessing
potential gaps between the changes of the various objects. It will be possible to
focus
a posteriori
on the spatial configuration of these evolutions: How are the
demographic trajectories of cities spatialized? Is there a regionalization of
the municipalities' poverty evolution? Where are the parcels that have resisted the
urbanization front?
Here again, it is interesting to draw a parallel with the points of view discussed
in Chapter 1. Galton [GAL 04] for example introduced two possible decompositions
for the spatio-temporal “field”. It can be seen as a sequence of temporal crosscuts
(
snapshots
), or as a juxtaposition of temporal trajectories of spatial entities
(Figure 3.3). Parallel to this distinction of an epistemological nature, the statistical
data will be laid out differently and/or different analyses will be mobilized
depending on the objective pursued.
Figure 3.3.
Spatial evolution: two points of view
Moreover, in an evolution analysis, whether it is about a spatial organization or
spatial entities, the issue of the reference arises: in relation to what is change being
observed? Any diachronic study is faced with this question, whose answer is often
not unique and depends on the point of view adopted to define the referential frame.
Let us take the example of a system whose elements are described by a single
variable, such as the cities of a region described by their resident populations at
the different censuses since 1800. The description of their absolute evolution, which
is through the number of inhabitants, or relative, in relation to the urban system that
they are part of, gives two different images of the urban growth (Figure 3.4). Let us
take the example of the Rhone valley urban system (France):
