Visualization of Digital Terrain Models

This research has been developed as a collaboration with the CNR institute IRRS (Research Institute on Seismic Risk), Remote Sensing Department, coordinated by Dr. Alessandro Brivio.

A digital terrain model can be reconstructed by interpolation of data from iso-elevation lines, or from a regular grid of elevation data reconstructed adopting stereo-images taken from aero or satellite survey.

The interpolation is based on linear and Kriging techniques; a fractal interpolation technique is also available. The interpolated DEM is the basis for the photorealistic visualization method.

The photorealistic visualisation is based on a smooth shading rendering, colour information associated to each terrain element is taken from remote sensed images of the reconstructed area. A classification of image pixels allows to recognise the typology of the terrain element, and to derive the RGB colour characteristic by the spectral signature of each terrain tipology.

TISS (Territorial Image Synthesis System) is an interactive program that supports a geologist to reconstruct and explore a DTM. The exploration is based on Virtual Reality methods, in particular walk through; also an animated virtual fly can be created interactively.

Future versions of the system will include utilities to explore the DTM, e.g. man made elements for environmental impact evaluation, cut&fill computation, erosion models, flood simulation, iso-elevation lines display etc.

The main display of the system; the area shown is the Khumbu valley in Nepal, close to the Everest mountain.(2M)

The animation interface window; same region.(2M)

A full screen view of Khumbu valley from the Everest. (2M)

A fly along the Khumbu valley. (100k)

A fly along the Aurina valley, at the border of Italian and Austrian alps. (160k)

References

• Brivio P.A., Marini D. and Righetti M,, "Fractal Based Technique for Mountain Relief Raconstruction", EARSel, Advances in Remote Sensing, 1, n. 3, VII pp 136-141(1992)

• Brivio P.A., Marini D., "A fractal method for Digital Elevation Model construction and its application to a mountain region". Computer Graphics Forum Vol.12 n.5 pp 297-309, (1993)

• Brivio P.A., Furini P., Righetti M., Marini D., "Synthesis of Multispectral Images of Natural Landscapes", in: Photorealistic Rendering in Computer Graphics Brunet P. Jansen F.W. Eds., Springer Verlag, New York, pp 240-250 (1994)

Acknowledgements: this work is the result of the contribution of many students: M. Righetti, P. Furini, F. Osculati, V. Cristanini; the interactive systems has been done by Luca Solda. The satellite data and the terrain elevation samples of the Everest area have been provided by EV-K2-CNR project.

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