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International cooperation and technology transfer
Mussio, Luigi

M. A. Brovelli(*), F. Migliaccio(**) and V. Tornatore(”)
O Politecnico di Milano, Facoltà di Ingegneria di Como [maria@ipmtf4.topo.polimi.it]
(**) Politecnico di Milano, DIIAR - Sez. Rilevamento
[federica@ipmtf4.topo.polimi.it; vin@ipmtf4.topo.polimi.it]
KEY WORDS: Geographic Information System, Data Base Management Systems, Spatial Extensions, Geoid
The following work is part of the International Geoid Service (I.Ge.S) project aiming at the use of GIS technology in
geodetic applications. The variety of the information needed for the calculation and management of the geoid suggests
the use of a DBMS-oriented storing method instead of a file-based one; this allows for a simpler and best structured way
to implement the most frequently used actions like updating and querying. The choice of the spatial database (differently
from other traditional DBMS like, for example, a business administration one) carries the peculiarity of the spatial aspect
that must be considered while planning the archive itself, in order to obtain a more efficient management system.
Particularly the relational database management systems supporting the most used GIS-engine interfaces, must have
extra features such as spatial extensions. In our presentation we will analyse this aspect referring to the construction of a
geographical information system for the geoidal undulations management.
In our presentation we will focus on the problems and
methods related to data structures, e. g. the detailed
practical description of spatial phenomena, referring to the
logical level of modelling. So, we are not interested in the
data modelling of geodetic information, i.e. the set of
conceptual tools necessary for organising our data.
To this purpose we would like only to remind that, as in
territorial information systems devoted to preprocessing
and analysing other kind of georeferenced data (e. g.
Land Information Systems -LIS- or Automated Mapping/
Facilities Management systems - AM/FM-) the information
layers we need to describe the data can be vectorial
(points, arcs or polygons layers) or raster (see Table 1).
Vector (line)
Coast lines
Vector (point)
Observed gravity anomalies
Vertical deviations
Ellipsoidal heights
(GPS measurements)
Orthometric heights (levelling
Digital terrain models
Gravity anomalies (model)
Gravity anomalies residual
terrain corrections
Geoid estimated by RTC
Geoid residual calculated via
Fast Collocation
Geoid (model)
Digital terrain models
Crustal density models
Moho depth models
Tab. 1 - Examples of vector and raster layers.
If we look, for instance, at the coastal lines and we
consider the subdivision between land and sea, we may
introduce a vectorial complex polygons layer for the
geometrical and topological description of the territory.
By the way, the majority of our data may be modelled by
means of point entities or cell layers. To the first group
belong observations of different kinds (for instance the
gravity anomalies or the geoid heights obtained by
comparison of GPS measurements and levelling) and
data interpolated in sparse points. To the second group
belong all gridded data, such as the reference geoid
computed by global collocation (e.g. the ITALGE095
geoid), the DTMs and the map of crustal density. So, with
respect to data manipulation, extraction and recovering
we have to face all the problems related with the
geographical features description and we need to
interface the GIS engine we have chosen to adopt for
geodetic purposes with an RDBMS which presents
special extensions allowing for an efficient management
of our database.
As referred in previous works (Biagi et al, 1998; Biagi et
al, 1999) the GIS we have selected in order to customize
it for geodetic purposes is the GRASS system.
This system was originally designed and developed by the
Environmental Division of the U. S. Army Construction
Engineering Research Laboratory. Since the first release
in 1985, it was distributed with source code, in such a way
that users from different sides (education and research
institutions, government organizations and private firms)
and with various interests (land planners, landscape
architects, geographers, geologists, ...) may customize
this software to settle their own questions. Furthermore,
as it was (and is) freely available, the number of users
and the types of applications in the research environment
have rapidly grown. From 1997 the GRASS development,
support and enhancement of public domain version, was
undertaken by the GRASS Research Group - Department