Digital Earth Reference Model
Frequently abbreviated DERM a Digital Earth model uses a well defined discrete partitioning or grid of cells to model the Earth, as opposed to a continuous point based model developed for navigation of traditional geographic coordinate reference systems.
A Digital Earth Reference Model tends to encompasses four critical principals of a digital model namely:
- A discrete uniform partitioning also called a Geodesic Discrete Global Grid System (a tessellation or tiling of cells over the Earth surface). Criteria for an optimized discrete global grid has been proposed by Michael Goodchild - generally, equal area cells that exhaustively cover the globe in closely packed hierarchical tessellations, each cell representing a homogeneous value:
- A unique linear non floating point index for each discrete cell that encompasses within the index both a parent child hierarchical relationship and a coordinate system that converges uniformly to the set of all real numbers;
- A set of mathematical relationships and operations built on the index: algebra, geometry, Boolean operations, image processing, etc; and
- Drawing on signal processing theory, a strategy for quantizing values (preferable integers) from analog or other digital sources to each discrete cell.
A DERM is designed to work in a digital environment providing statistically valid sampling, rapid storage, processing, transmission, discovery, visualization, integration, aggregation, and transformations. See: DERM in action.