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Raster Data Model

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raster data model
See Also: vector data model
[data models] A representation of the world as a surface divided into a regular grid of cells.


The Raster Data Model
The Raster data model is the simpler of the two and is based on the division of reality into a regular grid of identically shaped cells. Each cell is assigned a single value which represents the attribute for the area of that cell.

4.1 Raster Data Models
Learning Objective
The objective of this section is to understand how raster data models are implemented in GIS applications.

Raster data model:
Continuous numeric values, such as elevation, and continuous categories, such as vegetation types, are represented using the raster model. The raster data model represents features as a matrix/lattice of cells in continuous space.

raster data model
A representation of the world as a surface divided into a regular grid of cells. Raster models are useful for storing data that varies continuously, as in an aerial photograph, a satellite image, a surface of chemical concentrations, or an elevation surface.
raster dataset ...

The ~ has become the primary spatial data source for analytical modeling with GIS. The ~ is well suited to the quantitative analysis of numerous data layers.

vector and raster data models
field and object data models
representations for fields - pointgrids, contours, TIN data models
even data structures such as GBF/DIME and chaincodes have been called data models (Peuquet 1990) ...

Both vector and raster data models use LIDAR data. Many GIS programs have automated routines that convert the x, y, and z (elevation or altitude) points first into vector point files, ...

In this section the implications of vector and raster data models on encoding, storage, and analysis are discussed. The inherent statistical characterizations of mapped data and their implications in map analysis are described.

A DEM held as a regular matrix suffers the same disadvantages due to size as does the raster data model.

Grid layers are graphical representations of the ArcGIS and ArcInfo implementation of the raster data model. Grid layers are stored with a numeric value for each cell. The numeric cell values are either integer or floating-point.

While it is recommended that software incorporate both vector and raster data models, priority should be given to vector data model capabilities.

I would suggest you explore the Object-relational database, the ESRI website, the vector and raster data model, geostatistics or spatial statistics, topology or geospatial topology, and the open-geospatial consortium (OGC) website.

For example, the vector data model represents geography as collections of points, lines, and polygons; the raster data model represents geography as cell matrixes that store numeric values; and the TIN data model represents geography as sets of contiguous, nonoverlapping triangles.

The ~ is composed of a grid and each cell within the grid holds data. Another way to explain it is that the polygon has a grid laid over it and the polygon would fill those cells with data, each cell in the grid being assigned a value.

Each point feature is represented as a single coordinate pair, while line and polygon features are represented as ordered lists of vertices. Attributes are associated with each vector feature, as opposed to a raster data model, which associates attributes with grid cells.

With the raster data model, spatial data is not continuous but divided into discrete units.
Rubber Sheeting: A procedure to adjust the coordinates of all the data points in a data set to allow a more accurate match between known locations and a few data points within the data set.

See also: See also: What is the meaning of Data Model, Raster Data, Raster, Model, GIS?

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