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INTERACTIVE VISUALIZATION OF TERRAIN MODELS AND ORTHOPHOTOS
Lionel Dorffner, assistant professor
e-mail: ld@ipf.tuwien.ac.at
Institute of Photogrammetry and Remote Sensing, Vienna University of Technology
Gusshausstr. 27-29, A-1040 Vienna, Austria
tel: ++43-1 -58801 -12201; fax: ++43-1 -58801 -12299
Commission VI, Working Group 3 and Commission IV, Working Group 3 joint meeting
KEY WORDS: interactive, DTM, visualization, virtual reality, animation, VRML, SCOP
ABSTRACT
Nowadays, generating data of high quality and high accuracy is not sufficient any more for convincing
customers and sponsors. At least equally important is an appropriate and impressive way of data
presentation. As a consequence, an additional module to SCOP has been developed and implemented. The
new Animated Terrain Model (ATM) tool provides an easy way for preparing and exporting SCOP DTM
(Digital Terrain Model) data and orthophoto mosaics for interactive 3D visualization with the help of VRML.
As the VRML format was intended to be used for Internet applications, it has been designed to handle a
reasonably small amount of data. Therefore, the ATM development concentrated on processing and
interactive visualisation of extensive data sets as they are common in DTM and orthophoto applications. This
article describes the possibilities and limitations of the VRLM format in that context with the help of
spaceborne and airborne imagery.
KURZFASSUNG
Aufgrund der rasanten technologischen Entwicklung im Bereich der EDV reicht die Erzeugung von Daten
hoher Qualität und Genauigkeit allein oftmals nicht mehr aus, um Kunden und Geldgeber zu befriedigen.
Genauso wichtig ist es, diese in einer modernen, ansprechenden und beeindruckenden Weise präsentieren
zu können. Dieser Entwicklung Folge tragend wurde das SCOP Modul ATM (Animiertes Geländemodell)
entwickelt. Dieses ermöglicht auf einfache Weise die Aufbereitung von digitalen Geländehöhendaten (DHM)
und Orthophotos für eine interaktive Visualisierung basierend auf dem Datenformat VRML. Nachdem VRML
das Standardformat zur Beschreibung interaktiver virtueller 3D Welten im Internet ist, wird es primär für
kleine Datenmengen eingesetzt. Bei der Entwicklung von ATM wurde daher besonderes Augenmerk darauf
gelegt auch große Datenmengen, wie sie bei Verwendung von Geländemodellen und Orthophotos auftreten,
interaktiv visualisieren zu können. Dieser Beitrag beschreibt Möglichkeiten und Grenzen von VRML für
diesen Anwendungsbereich anhand eines realisierten Projektes.
1 INTRODUCTION
Today digital terrain models (DTM) and orthophotos
are both standard product of photogrammetric
restitution. The quality of the terrain model - and
furthermore of the orthophoto - depends on the
technique used for primary data acquisition as well
as on the software used for generating and storing
the terrain data structure.
For the acquisition we can distinguish between the
following methods [Gruen A., 1998]:
digitization of maps (simple way, sometimes
necessary if no other sources are available -
only usable, if old maps already exists)
tachymetry (method of engineering surveying -
only viable for small areas)
aerial photographs (traditional method - best
tested and proved to give good and accurate
results)
laser scanning (new and promising technique,
especially for deriving surface models - very fast
although not fully tested yet)
other remote sensing techniques (best suited for
very large areas, where high accuracy is not of
main interest.)
The most relevant forms of discrete terrain
representation are:
regular grid (simplest representation, often the
result of automatically generated DTMs on
Digital Photogrammetric Stations - contains no
further structure information, only 2.5D, compact
storage capability)
