Abstract
Digital Earth frameworks provide a tool to receive, send and interact with large location-based datasets, organized usually according to Discrete Global Grid Systems (DGGS). In DGGS, an indexing method is used to assign a unique index to each cell of a global grid, and the datasets corresponding to these cells are retrieved or allocated using this unique index. There exist many methods to index cells of DGGS. Toward facility, interoperability and also defining a “standard” for DGGS, a conversion is needed to translate a dataset from one DGGS to another. In this paper, we first propose a categorization of indexing methods of DGGS and then define a general conversion method from one indexing to another. Several examples are presented to describe the method.
Highlights
Digital Earth frameworks provide a multiresolution representation of the Earth as a spatial reference model with the ability to visualize, retrieve, embed and analyze data at different levels of detail [1].To assign data to locations and establish a multiresolution representation, the surface of the Earth is discretized using different methods
Various types of indexing exist to index cells of Discrete Global Grid Systems (DGGS), they are typically derived from three types of general indexing mechanisms: we call indexing methods that benefit from the hierarchy of cells provided by the refinement hierarchy-based indexing methods
To apply a 2D indexing method on a polyhedron for DGGS, the polyhedron can be unfolded to a 2D domain and the axes defined for the entire 2D domain or each face can be given its own coordinate system [20,37,38]
Summary
Digital Earth frameworks provide a multiresolution representation of the Earth as a spatial reference model with the ability to visualize, retrieve, embed and analyze data at different levels of detail [1]. To assign data to locations and establish a multiresolution representation, the surface of the Earth is discretized using different methods. Taking equal length steps along the latitudes and longitudes parametrizes the Earth into quadrilateral cells. These cells have difference sizes and become smaller approaching the poles. DGGS differ based on their initial polyhedron, cell type, projection and indexing method. These DGGS need to communicate and receive, share and integrate data coming from other DGGS.
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