CIPA 2003 XIX th International Symposium, 30 September - 04 October, 2003, Antalya, Turkey
performances and the user interface and to make it suitable for
a productive context.
The main developments of the software that concern the
adaptation of the program to the quality of the data that have
to be processed, the development of a routine set to help in the
production, the adoption of optimised solutions to automate the
process and the setting up of the user interface in Windows are
here described.
2. GENERATION OF A DDEM FROM A 3D MAP
It is by now known [Boccardo et al., 2001] that two series of
initial data are necessary to produce a true digital orthophoto:
maps, whenever they already exist. It should be considered that
this cartography is increasingly available in most of the towns,
both as a cartographic base for urban planning and as a
geometric base for local GIS. A 3D digital cartography
describes the territory and buildings in planimetry and heights
and therefore contains all the information that is necessary to
generate the corresponding DDEM:
• the natural ground surface is described through spot
heights and contour lines;
• artificial objects are represented through vertices known
in the 3 co-ordinates (roads, bridges, and railways are
described by polylines whose vertices are known in XYZ);
• a set of digital images with known internal and external
orientation parameters (obtained through bundle block
adjustment or through direct methods based on GPS/INS
integrated sensors) so as to guarantee the most complete
photographic coverage of the territory as possible;
• the correct description of the surfaces that can be
obtained, alternatively, through a traditional DEM,
complete with break-lines, a digital surface model (DSM)
composed of surface geometric primitives or a dense DEM
(DDEM):
• buildings are described as distinct volumes of equal
height, on whose inside a spot height (“centroid”) is
associated. In this way, buildings can resemble to solid
shapes (whose base is the boundary of the building)
extruded out of the terrain up to the height of the
associated centroid.
An example of 3D cartographic elements is given in figure 1
[Spalla, 2002]
Figure 2. Some of the user interface windows
2.1. The GeneDDEM software
Figure 1. An example of 3D digital cartography
This latter is often the easiest and cheapest solution to operate.
It in fact does not require heavy restitution or editing
operations, it does not use sophisticated software based on the
management of complex relational and logical databases, and it
can easily be acquired using modem instruments (laser
scanners) or, in a cheaper way, using interpolation from 3D
The GENEDDEM software, which has been developed in
Visual FORTRAN language, uses the information that derives
from a digital map to generate a dense DEM of the territory.
The input data that are necessary are those that are found (or
that have to be integrated) in a 3D digital map in DXF format,
with the description of the geometry (in which all the areas are
described by closed 3D polylines) and a list of the codes
inherent to spot heights, contour lines, various types of
