page_title: Discrete global grid
section_title: Hierarchical grids
hierarchical_section_title: Discrete global grid / Types and examples / Hierarchical grids
caption_attribution_description: English: Adapted from File:Great_Britain_Box.svg
context_page_description: A Discrete Global Grid is a mosaic which covers the entire Earth's surface.
  Mathematically it is a space partitioning: it consists of a set of non-empty regions that form a partition of the Earth's surface. In a usual grid-modeling strategy, to simplify position calculations, each region is represented by a point, abstracting the grid as a set of region-points. Each region or region-point in the grid is called a cell.
  When each cell of a grid is subject to a recursive partition, resulting in a "series of discrete global grids with progressively finer resolution", forming a hierarchical grid, it is named Hierarchical DGG.
  Discrete Global Grids are used as the geometric basis for the building of geospatial data structures. Each cell is related with data objects or values, or may be associated with other cells. DGGs have been proposed for use in a wide range of geospatial applications, including vector and raster location representation, data fusion, and spatial databases.
  The most usual grids are for horizontal position representation, using a standard datum, like WGS84. In this context, it is common also to use a specific DGG as foundation for geocoding standardization.
context_section_description: The right aside illustration show 3  boundary maps of the  coast of Great Britain. The first map was covered by a grid-level-0 with 150 km size cells. Only a grey cell in the center, with no need of zoom for detail, remains level-0; all other cells of the second map was partitioned into four-cells-grid (grid-level-1), each with 75 km. In the third map 12 cells level-1 remains as grey, all other was partitioned again, each level-1-cell transformed into a level-2-grid. 
  Examples of DGGs that use such recursive process, generating hierarchical grids, include:
caption: Successive space partitioning. The grey-and-green grid in the second and third maps are hierarchical.
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