262
J. Populus et al.
phytoplankton and hydrodynamic model simulations, etc... Cross analysis of these
layers should provide adequate advice for the better use of both environment and space.
Material and Methods
THE GIS PLATFORM
ArcView was selected as the GIS platform for the project, whereas Autocad was
selected for the digitization of cadastre maps. During data implementation, the formats
.dwg and .dxf were successively used, then transformed into Arcinfo coverages and
ArcView
The shapefile is an ESRI proprietary format that, unlike a
coverage, does not store the topology, which makes it a lot easier to manipulate. When
the topology is needed, it is computed locally. Tabular data remain unchanged from the
coverage format. Raster data may be imported into ArcView and stored either as a
or as an image. Grids, which keep pixel values inside a table, can be
manipulated using the ArcView extension
through various
functions : slopes, isolines, enhancement, area summarizing etc...
SCRIPT DEVELOPMENT
When clean data sets are ready for use in an ArcView project, it is desirable for the
end-user to perform his spatial analyses using only resident functions. The software
offers a number of standard facilities, plus a wealth of scripts that only need to be
copied from the library and run for specific purposes. For instance, to make the union
of several identical shape files, a specific script has to be invoked, are not available in
the interface toolkit. When the script has been loaded, if recurrent use is needed, it may
easily be either iconised in the ArcView interface or made resident in the project.
However, as little code as possible was written in the course of the project.
THE REFERENTIAL
In coastal zone mapping the Mercator projection system is the current one used for the
purposes of navigation. Inland, the French IGN (Institut Géographique National) uses
the Lambert conformal conical projection. Considering this, and also its links with
other data sources and its potential users, the latter land-based reference was more
appropriate than a maritime one. The Lambert projection was also adopted by the local
services of the Ministry of Transport in charge of dredging and harbour maintenance,
in particular for depth surveys.
THE INTERPOLATIONS
Interpolation is required when values of a given variable are needed at locations
without measurements. This is the case here for the output of depth soundings surveys,
where point samples have to be made into either a grid file or isolines. It may also
J. Populus et al.
phytoplankton and hydrodynamic model simulations, etc... Cross analysis of these
layers should provide adequate advice for the better use of both environment and space.
Material and Methods
THE GIS PLATFORM
ArcView was selected as the GIS platform for the project, whereas Autocad was
selected for the digitization of cadastre maps. During data implementation, the formats
.dwg and .dxf were successively used, then transformed into Arcinfo coverages and
ArcView
The shapefile is an ESRI proprietary format that, unlike a
coverage, does not store the topology, which makes it a lot easier to manipulate. When
the topology is needed, it is computed locally. Tabular data remain unchanged from the
coverage format. Raster data may be imported into ArcView and stored either as a
or as an image. Grids, which keep pixel values inside a table, can be
manipulated using the ArcView extension
through various
functions : slopes, isolines, enhancement, area summarizing etc...
SCRIPT DEVELOPMENT
When clean data sets are ready for use in an ArcView project, it is desirable for the
end-user to perform his spatial analyses using only resident functions. The software
offers a number of standard facilities, plus a wealth of scripts that only need to be
copied from the library and run for specific purposes. For instance, to make the union
of several identical shape files, a specific script has to be invoked, are not available in
the interface toolkit. When the script has been loaded, if recurrent use is needed, it may
easily be either iconised in the ArcView interface or made resident in the project.
However, as little code as possible was written in the course of the project.
THE REFERENTIAL
In coastal zone mapping the Mercator projection system is the current one used for the
purposes of navigation. Inland, the French IGN (Institut Géographique National) uses
the Lambert conformal conical projection. Considering this, and also its links with
other data sources and its potential users, the latter land-based reference was more
appropriate than a maritime one. The Lambert projection was also adopted by the local
services of the Ministry of Transport in charge of dredging and harbour maintenance,
in particular for depth surveys.
THE INTERPOLATIONS
Interpolation is required when values of a given variable are needed at locations
without measurements. This is the case here for the output of depth soundings surveys,
where point samples have to be made into either a grid file or isolines. It may also