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nonetheless a same phenomenon can fall under different categories depending on the
point of view adopted.
Brogaard [BRO 98] for her part uses granularity as a filter to distinguish between
two types of fields, one refers to a complete continuity while other refers to objects
at a certain level of scale. She illustrates this latter case with the example of
population densities. A density field is extrapolated from regions sufficiently thin for
the density to be either 0 or 1, depending on whether an individual is present or not
on these portions of space. Thus, the existence of this field is subject to the existence
of individuals who serve as the basis for the measurement of the density, and which
are “material objects”. She opposes this type of field to the one where the subject of
interest is the salt concentration of a lake: there is only one portion of space where
this concentration has a meaning, that of the lake, and the lake as well as the
distribution of the salt in the lake are of a field kind. Brogaard proposes
consequently to distinguish two types of geographic fields: - the fields that depend
on the objects located in this field (“object fields”), the example being that of the
population density; - the fields that depend on fields (“continuity fields”), the
example being that of the salt concentration.
In general, we can also distinguish two types of objects: -
fixed
objects, whether
they are clearly distinguishable from their environment (a tree or a building) or
whether they are part of it (example of the hill above, or even of a river); -
mobile
objects, which move in space (for example, pedestrians, automobiles and ships),
space playing then the role of support. Here again, going from an object type to the
other can be a question of observation granularity. The spatial envelope of a
demonstration, for example, may, therefore, be captured as a fixed object from an
aerial photo, and this envelope can have fixed contours while the demonstrators,
mobile objects, move in all directions.
1.1.4.
An example of empirical objects' construction: the case of cities
Here, we propose to illustrate the different stages that are associated with the
passage from the conceptualization of objects to their concrete construction (this
passage corresponds to the operationalization), mobilizing observables in the
framework of databases. The “city” is a good example, and it even constitutes a
quasi-iconic case in geography, of a built object
8
[BRE 13]. The passage from the
conceptual object to the empirical object is not generally done directly and needs
giving account of the construction process.
8 This example is drawn from multiple experiments led by Anne Bretagnolle: ANR Harmoni-
cities http://www.parisgeo.cnrs.fr/spip.php?article38&lang=en) and ESPON DB program -
urban data (http://www.espon.eu/main/Menu_ToolsandMaps/ESPON2013Database/).
