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Geomorfometria - parametry morfometryczne w charakterystyce rzeźby terenu

Wieczorek M., Żyszkowska W.

Polski Przegląd Kartograficzny

2011

T. 43, nr 2

130-144

Autorki przedstawiają geomorfometrię jako dziedzinę związaną z określaniem morfometrycznych cech powierzchni terenu, jej podstawowe problemy oraz metody oparte na numerycznych modelach terenu.

Morphometry, which has been accompanying geography sińce 19th century, establishes numerical parameters describing Earth surface relief. Every type of measurement is conditioned by certain methodological assumptions which determine the way they are conducted. In the process it is very important to adjust the scale of the elaboration to the size of forms under analysis and to the goal of research. The choice of the size of reference units in which morphometric parameters are determined is equally essential. A.F. Pitty (1969), A.J.W. Gerard and DA. Robinson (1971) stressed the relation between the calculated slope angle and the size of the interval in which the angle is measured, even during measurements in open terrain. Morphometric parameters in traditional morphometry were determined on the basis of contour-line image of relief. Slope and slope aspect were then determined. Nowadays, the parameters are calculated on the basis of digital terrain models in the form of TIN or GRID. The article presents the algorithms for calculation of slope and slope aspect with the use of raster model. Depending on the number of adjacent grids considered in calculations, the algorithms for the determination of slope and slope aspect base on two, three, four, eight and nine points (P.L. Guth 1995). Among basic attributes of topographic surface describing the shape of the slope is surface curvature,

An interactive modification data structure for 3D surfaces

Madi M., Walton D.

Machine Graphics and Vision

2003

Vol. 12, No. 3

293-310

The design and display of 3D models on a computer screen is usually interleaved by a series of data manipulations. Data are usually sets of 3D points that make up polygonal patches in the composition of polyhedral models. Manipulations are the transformation operations that are applied to points to facilitate design and visual understanding of the graphical models. To further facilitate and speed up the design phase, methods are proposed to interactively segment and modify selected sub-surfaces, thereby limiting the number of patches that need to be manipulated for computationally cheaper and faster results. This paper illustrates how polyhedral surfaces can be organized into special data structures to facilitate rapid selection of vertices, and how those same surfaces can be segmented into sub-polyhedra for zooming and vertex manipulation during design, and can then be re-introduced as modified segments into the original structure. Algorithms and visual examples are also provided to support the work.