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A NEW PERSPECTIVE FOR THE VISUALIZATION OF CARTOGRAPHIC DATA
V. Tsioukas!, K. Papadopoulos®, M. Daniil', E. Daniil^
"The Aristotle University of Thessaloniki, Greece, Dept. of Cadastre, Photogrammetry and Cartography,
National Center for Maps and Cartographic Heritage, Greece
Email : tsioukas @egnatia.ee.auth.gr, kostas @maplibrary.gr
Commission V, Working Group V/6
KEY WORDS: 3D Map, visualization
ABSTRACT:
In a conventional map cartographic data are considered two-dimensional information that are used for navigational, educational and
many other reasons. A conventional map is usually printed on
paper in some certain and unchangeable scale. However a modern
map is created using digital techniques and after it has been processed in a computer, it is printed on paper. Digital equipment
provides many more opportunities to visualize information that is embedded on a map.
The most important aspect that is presented in this paper is the use of the depth information (third dimension) that is usually drop out
and is not visible on a conventional map. The visualization techni
adopted to produce an innovative type of data: 3D map.
1. INTRODUCTION
Cartographic data, namely the maps have been used for various
reasons during the years of their use. Their main usage was for
navigational reasons especially for travellers. However the
maps are not only constructed as a tool for navigation through
the seas and the land. A map plays also the role of an
information bank that demonstrates the features (thematic
information) of a region on the earth using toponyms and
specific symbols, showing the exact location (X, Y and in some
cases Z coordinates) of these features on it.
Generally speaking, a map is considered to be a 2D information
base that is produced from the orthogonal projection of the
main features of the 3D object space on paper using a specific
scale. These are also the main characteristics that appear when
creating a map:
e The rejection of the depth information of the 3D
world on the map
e The creation of a product that represents information
(with various importance levels) on the map in some
unique ant non alterable scale
Many maps allow the presentation of 3D information of the
mapped region using either contour lines or an image
background containing variations of colours. This depth
information (through contour lines or using coloured variations
of the background image of the map) is not a standard feature
that appears on a typical map. It has been very difficult to
embed 3D information on paper. On the other hand, the contour
lines do not provide an easy way to extract the 3D information
of the mapped objects. That's why new techniques must be
introduced to provide an easy way to demonstrate all the
valuable information of a map using a real 3D product.
2. COMBINATION OF CARTOGRAPHIC DATA WITH
IMAGE DATA
With the advent of the digital era almost 10096 of the maps are
created using the computers’ technology. Photogrammetry
plays a very important role in this procedure, since it supplies
the georeferenced digital images that are finally digitised and
they provide the map of a region of the earth’s surface.
ques that are used to present photogrammetric products have been
Typical photogrammetric products are the Digital Elevation
Model (DEM) of the imaged objects and the digital orthophoto,
which present the object space in the same way as a map. The
post processing of the digital orthophoto can certainly lead to
the creation of a map using CAD Software applications. For
example, the orthophoto (raster information) can be digitised
and supply the vector information i.e. road, rivers, etc and many
other geophysical features of a map.
Raster and vector information of a map can be combined using
advanced image processing software applications such as
CorelDraw and Adobe Illustrator. In this way a digital map of a
region of Mt. Athos in Greece has been created as it is
illustrated in fig.1.
The fussed image of the raster and vector data can be used to
drape the object’s model that has been created from the DTM
derived from the digitization of the contour lines of a map.
This technique has been used quite a lot lately and has given
some very good visualization products of photogrammetric data
and has also given virtual reality models (VRML) of the imaged
object.
Instead of using the ortho image for the draping of the model,
its combination with the vector image has been used. This way
it has been accomplished to place in their exact location the
whole set of cartographic data (i.e. roads, rivers, etc) since they
are placed on a surface that is an actual 3D model of the real
object and not on a just plane surface. An innovative kind of a
map is created that we call a 3D map.
3. VIDEO CREATION
Additionally to the created 3D map that is only available
through a CAD-CAM software application a video file that
presents a virtual fly-over on the maps data can be created.
Many researchers have used video files to visualize
cartographic data but not many of them have combined
cartographic and photogrammetric products to produce an
animation around a 3D object’s model. The final product that
has been produced in our case consists of a sequence of images
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