Geoscience Reference
In-Depth Information
framework, and here we are recalling it to distinguish between two points of view on
geographical space:
-the “discrete” or “object-oriented” point of view is more easily
conceptualizable because it is well-anchored in common language [GAL 03]:
individual beings, buildings and roads are objects of common sense, relatively easy
to identify in the sense that they are “distinguishable” from their environment and
associated with an identity. Once built, objects of the “fiat” type, such as cities or
countries, share these properties and can be conceptualized by an object approach, of
the atomistic type. The totality of these objects exists independently from their
attributes, and they retain their identity when manipulated;
- the “continuous” or “field-oriented” point of view is often the work of
geoscience or environmental science specialists. As a matter of fact, such approach
is appropriate for geographic information that is presented in continuous form, for
example, about land use or temperature. Space can then be conceptualized as a set of
localizations to which attributes are attached (“a spatial field is a mapping of spatial
locations to values”, [GAL 04]). The nature of the information associated with
localizations can be of any kind, qualitative (land use) as well as quantitative (for
example, temperature and hydrometry degree). The most important thing is that the
field
perspective refers to a coverage of the space.
The adoption of one of these two points of view rather than the other depends
either on the
a priori
position of the researcher or on his choice in front of a specific
objective in which he considers one of the approaches more appropriate than the
other. Most of the spatial phenomena can effectively be conceptualized from either
an “object” or a “field” perspective: thus, a vegetation cover can be apprehended as
consisting of objects, such as prairies or woods at the landscape scale, or of trees and
shrubs at a finer scale or as a continuous field covering a given space [PEU 88,
PEU 98]. Another example is forest fire that can be formalized as an object moving
in space, or as a continuous field of fire intensity. The two perspectives are
associated with different conceptions of space. In one case, the object is
autonomous, it has its own attributes and space is a support, a referential frame in
which the objects are positioned: “imposed upon” underlying fields according to
Galton ([GAL 03]). The objects become to some extent the inhabitants of a space
that would be otherwise empty. In the other case, the field forms a “plenum”, where
each localization is attached to a property: we are then faced with what Couclelis
[COU 92] called a “continuous fabric”. In practice, it is possible to extract objects
from a “field-based” approach: the objects are carved out from the properties
attached to localizations. These objects can then be characterized in turn by the
appropriate attributes. Thus, Plewe [PLE 98] gives the example of the hill. It may be
represented as a field of altitudes and is not delimited by a sharp border in nature;
there is a gradation. On the other hand, if we want to represent it as an object, one is
led to determine an altitude threshold and then delimit the hill with a clear and sharp
