Systèmes d'information géographique. Dossier ... - CiteSeerX

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requirement leads us to look for the complementary nature of the information to these
different scales within the urban GIS.
The practical result of this type of approach is a large increase the demand in terms of basic
information on different scales. Since most of the tools used till now gave priority to a single
scale approach (classic cartography, quantitative analyses, etc.) thereby prohibiting an
integrating approach, the GIS, by providing the ossibility of making the information relating to
the territories cohabit with different scales, offer an enhanced capacity for processing. Is it
then suffice to make them operational in multi-scale analysis procedures ?
An example for situating the capacities of the tool with the theoretical process raises
problems of two kinds : the former deal with the multi-scale processing methodologies, the
latter the geographical data themselves and their pertinence.
The GIS and the multi-scale processing
There is in fact a significant difference between the real capacities for making geographical
data from different scales correspond in the GIS, and the scope of their joint use in terms of
analysis, the significance of combined processing of this type are still easy to criticise.
If the GIS are capable of storing layers of information corresponding to the different territorial
layers, their capacities to convert the complementary nature of the spaces tends more
towards a possibility of successive zooms than to a real possibility of combined processing.
This criticism does not address the conception of the tool itself, but rather the methodological
scope of such processing with regards to the types of information available.
From the very fact that the cartographic tradition from which GIS are taken, the scale
translates in these tools, a notion of graphic bottlenecks much more than a thematic
complementary nature.
The whole of these remarks systematically go back to the basis itself for processing and
analysis : the geographical information, proving, once again, that the true gamble in the GIS is
less their potential than the validity of the elements that they handle.
Pertinence of the geographical data
in an urban environment
Some people have talked on the subject of urban data for "imperfect formation of the data"
(Prouzet, Hernandez, 1995) by demonstrating the risks for data bases being either oversized
or undersized with respect to the problems of urban management and planning.
Nowadays there is a deep gap today between the need for the "polymorphism" 14 of the data
which would respond to the multi-scale process needed for the strategic action, and the
reality of the supply of digital data on which the weight of history weighs considerably and still
today constitutes, in a certain way, a brake to the achievement of operational methods for
taking full advantage of the possibilities opened up by the GIS.
14 Gaudemar (1992).