Geoscience Reference
In-Depth Information
Careful analysis of direct contours generalization methods reveals that they
are harder to implement than indirect methods based on DEM generaliza-
tion because of necessity to consider topological relationships between
lines (Zhang et al. 2007), complexity of structure lines derivation (Ai
2007) and interpolation difficulties when contour interval in resulting
DEM should be different (Peled et al. 1989).
There are also advanced techniques for TIN generalization using morpho-
logical criteria (Pedrini 2001, Wang et al. 2008). Hierarchical or pyramidal
multiresolution models provide generalization mechanism for derivation of
intermediate levels of detail (de Floriani et al. 1996). Great attention is
paid to global hierarchical models since the amount of detailed information
is growing irrepressibly (Bernardin et al. 2010)
Most investigations related to visualization of multiresolution DEMs are
oriented on morphometric and hydrologic analysis (Wood 1996, Dragut
et al. 2009) and demonstrate results as thematic images in variety of scales.
On the whole there is a lack of methods for multiscale relief mapping and
visualization, not DEM generalization and analysis. Our methodology is
intended to bridge this gap and make relief image the full-fledged element
of multiscale maps.
2- Approach and methods
2.1 Scales and projection
As multiscale map can be viewed in a continuous set of scales, there is
obvious need in control of map appearance while scale changes. It can be
made more consistently if scale range and scale series of map are defined.
Scale range defines space between largest and smallest map scales in
which generalization take place. It should cover suitable scales for relief
forms that will be studied and allow wide field of vision to study neighbor-
ing relationships between forms. Below and above scale range map image
will be simply reduced or enlarged.
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