The most important attribute in each dataset is type of object
which classified objects into several classes depended either by
their width, structure or significance. Roads, as example, are
classified in classes based on their importance and
transportability such as motorway, state road, pathway, fair
weather track, etc. This attribute allowing us to represent object
in adequate form. Other attributes are not matter of importance
for representation and are removed due to faster processing and
saving of space.
Very important content of each map are human made objects as
instance: buildings, ruined buildings, churches, airports, etc.
Those objects are not present in GKB25. Due to lack of
generalization was impossible to use existing datasets as:
cadastral of buildings or database of house numbers. For our
project all human made objects were vectorized from the
National topographic map at scale 1: 25,000 and they don't
have any attributes.
A geometry of all datasets in the GKB25 has only 2D
coordinates and because of that they are not suitable for direct
3D presentation. The only dataset which contain height
information are contours with height as attribute. All previously
existed DEMs of Slovenia were not suitable for 3D presentation
of GKB25 datasets, due to position incompatibility or
insufficient resolution, so it was decided that a new, so called
cartographic DEM from contour dataset will be produce. To
achieve that it was necessary to convert contours into 3D
coordinate system, later triangulate contours into triangle
irregular network - TIN with inferred breaklines and then
interpolate it in DEM. TIN was also improved by
implementation of height spots that were additionally
vectorized, geomorphologic valued and attributed and finally
added into GKB25 as new data layer. Final product of this
enhancement is a cartographic DEM with resolution of 10
meters - KDMR10 which is used as elevation basis for 3D
presentation of all other datasets.
3. PRINCIPLES OF SYMBOLICAL 3D
VISUALIZATION
A computer technology development and a wide range of
computer tools have brought many changes in theoretical
fundaments of cartography. Visualization techniques and
possibilities for communication between user and computers
give an opportunity to design new landscape representations.
They would enable users better terrain interpretation resulted in
more efficient and complete spatial data capturing
corresponding to the traditional two-dimensional paper or
screen maps. The main advantage of the computer technology is
direct terrain representation possibility in comparison to so far
existing ones, like contour lines, elevation tints, hill-shading and
others. A three-dimensional cartographic model can be
visualized as a three-dimensional or two-dimensional
presentation, so called 3D map. Principles for traditional 2D
maps design have been developed for decades and make strong
base for every map produced, while such principles for 3D
maps do not exist. An attempt for defining 3D maps’
cartographic design principles is one of the key research fields
in Slovenia, performed by the Geodetic Institute of Slovenia and
by the Chair of Cartography, Photogrammetry and Remote
Sensing at Faculty of Civil and Geodetic Engineering in
Ljubljana.
Two major map tasks are recognition of contents (metric and
semantic) and communication between the cartographer and the
user. In analogous cartographic technology there were no
differences between the cartographic model and the map itself.
Such cartographic model offers users direct recognition of
contents and it presents a direct communication medium
between the cartographer and the user. The cartographic model
is fixed (static) and the user can perform only some limited
changes in it. In computer technology the cartographic model is
a digitally written record of spatial data and it is not possible to
use it directly either for recognition or for communication
purposes. But, the user can influence the model by changing its
properties and make it applicable in the following ways:
visualization with various symbol sets, selection of elements
and objects which will be visualized, spatial transformations,
scale generalization, adding new data, including new users
oriented functions, format changing and more. Besides, these
computer made cartographic models offer many new additional
possibilities of use: simulations of moving in real time,
simulations of placing new objects on landscape, dynamic
phenomena analyses, etc. Digital cartographic models can
contain many more data than the analogous ones. Additional
data as specification tables, attributes, topological relations,
pictures, movies and sound can be added to individual objects
and elements. Data can be more heterogeneous; all the data
needed have the same accuracy, complexity, detail or depth.
There is no theoretical limitation of the size of the area
presented in model, but there are some practical limitations such
as amount of digital data. Main changes in contemporary
computer maps regarding traditional analogue maps are as
follows. The user can select any view directions instead of
mostly vertical, ground plan views. Possible options are:
vertical and almost vertical views, used for ground plan maps,
design should be as similar to the contemporary 2D maps as
possible; parallel to horizontal plane (profiles) and inclined,
orthogonal or perspective. Changed medium (monitor, paper
print) results in limited resolution, different colors, limited
format of image and different multimedia possibilities (1mage,
sound...). Users can interactively affect on the presentations
and last but not least, model should allow dynamic
presentations (animations) and presentations, depending on time
(Petrovié 2001).
International Cartographic Association defined a map as a
symbolized image of geographical reality, representing selected
features or characteristics, resulting from the creative effort of
its author's execution of choices, and is designed for use when
spatial relationships are of primary relevance (ICA, 1999).
According this definition a map not limited with medium, not
limited with type of perception (visual, audio, tactile) and also
not limited with view direction. Three-dimensional landscape
presentation can be called “a map” only if satisfies some
requirements, that worth for traditional “2D” maps, as follows:
- every presented object is defined with its geographical
position in selected coordinate system and this
position have to be accessible to the user,
- objects and phenomenon are projected from Earth
surface to the selected (usually plane) coordinate
system according exact cartographic projections, that
assured deformations in regulation sizes,
- cartographic symbols as “an alphabet” of the map
archive the communication and the information
transfer between cartographer and user and
- cartographic generalization principles define the level
of map detail.
Three-dimensional (3D) map is therefore cartographic
landscape presentation in perspective view, where topographic
objects and phenomenon are presented by cartographic symbols,
explained in a legend. Authors usually neglect those
requii
mathe
lands
objec
users
obser
Desig
needs
can 1
conte
and p
The
funda
space
mesh
They
distin
simile
we W
functi
Some
from
impor
differ
perspe
preser
resolu
are fa
maps
geome
(Rojc,
object
landsc
users.
struct
second
and u
visual
fractal
rock a
secon
coveri
consis
Additi
fact it
object
vertice
descri;
speaki
memo
The a
huge €
visuali
Every
two
cartog
maps
Bertin
bright
(Bertir
(point,
3D ob
the t
Geom:
man-ır