Abstract
AbstractThis chapter summarizes the theories and methods in continuous zooming for Digital Earth. It introduces the basic concepts of and issues in continuous zooming and transformation in scale (or multiscale transformation). It presents the theories of transformation in scale, including the concepts of multiscale versus variable scale, transformation in the Euclidean space versus the geographical space, and the theoretical foundation for transformation in scale, the Natural Principle. It addresses models for transformations in scale, including space-primary hierarchical models, feature-primary hierarchical models, models of transformation in scale for irregular triangulation networks, and the models for geometric transformation of map data. It also discusses the mathematical solutions to transformations in scale (including upscaling and downscaling) for both raster (numerical and categorical data) and vector (point set data, line data set and area data) data. In addition, some concluding remarks are provided.
Highlights
This chapter summarizes the theories and methods in continuous zooming for Digital Earth
Continuous zooming is a fundamental function of a Digital Earth, as the demand for such a function has been vividly portrayed -US Vice President Al Gore in his famous speech “The Digital Earth: Understanding Our Planet in the twenty-first Century” (Gore 1998): Imagine, for example, a young child going to a Digital Earth exhibit at a local museum
The cascade scene seen by the young child is a result of continuous zooming
Summary
Continuous zooming is a fundamental function of a Digital Earth, as the demand for such a function has been vividly portrayed -US Vice President Al Gore in his famous speech “The Digital Earth: Understanding Our Planet in the twenty-first Century” (Gore 1998): Imagine, for example, a young child going to a Digital Earth exhibit at a local museum. The cascade scene seen by the young child is a result of continuous zooming Such zooming can be realized by continuously displaying a series of Earth images taken at a given position and changing the focal length of the camera lens continuously or displaying images taken at different heights continuously but with at a fixed camera focal length. To make the display visually smooth, the differences between two images should be sufficiently small, the number of images in such a series is very large, which demands huge data storage. It is a very difficult, if not impossible, problem
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