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Manfred Wiggenhagen
DEVELOPMENT OF REAL-TIME VISUALIZATION TOOLS FOR THE QUALITY CONTROL
OF DIGITAL TERRAIN MODELS AND ORTHOIMAGES
Dr.-Ing. Manfred Wiggenhagen
University of Hanover, Germany
Institute for Photogrammetry and Engineering Surveys
wigge@ipi.uni-hannover.de
"» KEY WORDS: DTM/DEM/DSM, Real-time, Visualization, Quality-Control
ABSTRACT
This paper presents the results of software development for the visualization of three-dimensional data sets using
moderns OpenGL libraries and the programming language C/C++. The software tool has been tested under MS-
Windows '98 and Windows NT on Pentium II computers with graphic accelerator boards supporting OpenGL real-
time display.
KURZFASSUNG
Dieser Beitrag stellt die Ergebnisse einer Softwareentwicklng zur Darstellung von dreidimensionalen Daten unter
Nutzung moderner OpenGL Bibliotheken und die Programmiersprache C/C++. Das Werkzeug wurde unter
Windows '98 und Windows NT auf Pentium II Computern mit Graphikbeschleuniger-Karten getestet, die OpenGL
Echtzeitdarstellung unterstiitzen.
1 INTRODUCTION
Digital Terrain Models are produced in different resolutions and quality depending on the type of data acquisition.
Results from analytical photogrammetry, digital matching and laserscanning have to be compared and to be
visualized on the computer screen. To detect errors and to improve regularly stored Digital Terrain Models based on
plausibility checks, powerful computer based tools are required. In addition orthoimages should be displayed on top
of the terrain models to detect remaining distortions and discrepancies.
2 DESCRIPTION OF METHODS
For the real-time visualization of digital terrain models and orthoimages, an OpenGL library is used in a C/C++
programmed tool running under MS Windows (Claussen, 1997). The OpenGL library offers a great variety of
graphic functions for the fast and easy display of vectors, polygons and textures (Barth et al, 1996). In combination
with modern graphic accelerator boards a fast visualization of regularly gridded digital terrain models is possible.
2.1 Data Formats
Several data standards have been integrated. USGS DTM Format (USGS, 1992-1998), national data format and
additional fractal landscape formats are used for the terrain models. Texture images and orthoimages have been
integrated in Windows bmp-Format.
2.2 User Interface
A structured dialog box serves as the user interface to the visualization program. The project relevant inputs are:
Filename of digital elevation model (DEM), type of elevation data set and name of texture file. The group
Properties includes radio buttons for several cameras, type of texture mode and the type of polygon display. After
the DEM has been successfully loaded additional parameters are shown: the group DEM data includes information
about DEM origin, size and resolution in x and y .
International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B3. Amsterdam 2000. 987
