A georelational data model is a geographic data model that represents geographic features as an interrelated set of spatial and attribute data. The georelational model was the dominant form of vector file format during the 1980s and 1990s, including the Esri coverage and Shapefile. [1]
The second era in the history of GIS, starting in the mid-1970s, was characterized by the rise of the first general-purpose GIS software programs (rather than the bespoke systems created in the 1960s and early 1970s). Each of these programs also created its own data file structures, primarily focused on finding innovative ways to store the spatial or geometric aspect of the data in the most efficient and error-free way. One example of this was the POLYVRT software and data structure (1973) from the Harvard Laboratory for Computer Graphics and Spatial Analysis, which inspired the Arc/INFO Coverage format. [2] : 105 In experimental GIS software such as ODYSSEY, attribute data was only handled in a rudimentary way. Meanwhile, the relational database was quickly becoming the most promising software for managing non-spatial data, and several nascent GIS software companies chose to adopt it into their systems, especially Esri.
Although there were exceptions such as the object-oriented data models in Smallworld GIS (1989) and Intergraph's experimental TIGRIS, georelational data dominated the GIS industry until the rise of spatial databases in the late 1990s. Most of them are obsolete, although the Shapefile is still in common (if decreasing) use.
In any vector data structure, the core unit is an object (either a geographic feature or a sample location for a field) that has a location in space (of 0, 1, 2, or 3 dimension) and a set of attributes. In the georelational model, these are stored as separate files: a geometry file that is usually custom-designed by a software developer for use in a particular program, and an attribute table that follows relational database principles; often, the latter is adopted directly from an existing relational database management system software.
Examples of commonly-used georelational data formats include:
Environmental Systems Research Institute, Inc., doing business as Esri, is an American multinational geographic information system (GIS) software company headquartered in Redlands, California. It is best known for its ArcGIS products. With 40% market share as of 2011, Esri is one of the world's leading supplier of GIS software, web GIS and geodatabase management applications.
A coverage is the digital representation of some spatio-temporal phenomenon. ISO 19123 provides the definition:
In vector computer graphics, CAD systems, and geographic information systems, geometric primitive is the simplest geometric shape that the system can handle. Sometimes the subroutines that draw the corresponding objects are called "geometric primitives" as well. The most "primitive" primitives are point and straight line segment, which were all that early vector graphics systems had.
A GIS file format is a standard for encoding geographical information into a computer file, as a specialized type of file format for use in geographic information systems (GIS) and other geospatial applications. Since the 1970s, dozens of formats have been created based on various data models for various purposes. They have been created by government mapping agencies, GIS software vendors, standards bodies such as the Open Geospatial Consortium, informal user communities, and even individual developers.
TerraLib is an open-source geographic information system (GIS) software library. It extends object-relational database management systems (DBMS) to handle spatiotemporal data types.
A GIS software program is a computer program to support the use of a geographic information system, providing the ability to create, store, manage, query, analyze, and visualize geographic data, that is, data representing phenomena for which location is important. The GIS software industry encompasses a broad range of commercial and open-source products that provide some or all of these capabilities within various information technology architectures.
ArcSDE is a server-software sub-system that aims to enable the usage of Relational Database Management Systems for spatial data. The spatial data may then be used as part of a geodatabase.
The shapefile format is a geospatial vector data format for geographic information system (GIS) software. It is developed and regulated by Esri as a mostly open specification for data interoperability among Esri and other GIS software products. The shapefile format can spatially describe vector features: points, lines, and polygons, representing, for example, water wells, rivers, and lakes. Each item usually has attributes that describe it, such as name or temperature.
ArcGIS is a family of client, server and online geographic information system (GIS) software developed and maintained by Esri.
ArcInfo is a full-featured geographic information system produced by Esri, and is the highest level of licensing in the ArcGIS Desktop product line. It was originally a command-line based system. The command-line processing abilities are now available through the GUI of the ArcGIS Desktop product.
The Geospatial Data Abstraction Library (GDAL) is a computer software library for reading and writing raster and vector geospatial data formats, and is released under the permissive X/MIT style free software license by the Open Source Geospatial Foundation. As a library, it presents a single abstract data model to the calling application for all supported formats. It may also be built with a variety of useful command line interface utilities for data translation and processing. Projections and transformations are supported by the PROJ library.
MapInfo Pro is a desktop geographic information system (GIS) software developed by Precisely, used for mapping and location analysis. It was formerly developed by Pitney Bowes Software and the MapInfo Corporation.
ArcMap is the former main component of Esri's ArcGIS suite of geospatial processing programs. Used primarily to view, edit, create, and analyze geospatial data. ArcMap allows the user to explore data within a data set, symbolize features accordingly, and create maps. This is done through two distinct sections of the program, the table of contents and the data frame. In October 2020, it was announced that there are no plans to release 10.9 in 2021, and that ArcMap would no longer be supported after March 1, 2026. Esri is encouraging their users to transition to ArcGIS Pro.
ArcView, now referred to as ArcGIS for Desktop Basic, is the entry-level licensing level of ArcGIS Desktop, a geographic information system software product produced by Esri. It is intended by Esri to be the logical migration path from ArcView 3.x.
A geographic data model, geospatial data model, or simply data model in the context of geographic information systems, is a mathematical and digital structure for representing phenomena over the Earth. Generally, such data models represent various aspects of these phenomena by means of geographic data, including spatial locations, attributes, change over time, and identity. For example, the vector data model represents geography as collections of points, lines, and polygons, and the raster data model represent geography as cell matrices that store numeric values. Data models are implemented throughout the GIS ecosystem, including the software tools for data management and spatial analysis, data stored in a variety of GIS file formats, specifications and standards, and specific designs for GIS installations.
The following tables compare general and technical information for a number of GIS vector file format. Please see the individual products' articles for further information. Unless otherwise specified in footnotes, comparisons are based on the stable versions without any add-ons, extensions or external programs.
Geospatial topology is the study and application of qualitative spatial relationships between geographic features, or between representations of such features in geographic information, such as in geographic information systems (GIS). For example, the fact that two regions overlap or that one contains the other are examples of topological relationships. It is thus the application of the mathematics of topology to GIS, and is distinct from, but complementary to the many aspects of geographic information that are based on quantitative spatial measurements through coordinate geometry. Topology appears in many aspects of geographic information science and GIS practice, including the discovery of inherent relationships through spatial query, vector overlay and map algebra; the enforcement of expected relationships as validation rules stored in geospatial data; and the use of stored topological relationships in applications such as network analysis. Spatial topology is the generalization of geospatial topology for non-geographic domains, e.g., CAD software.
The Esri TIN format is a popular yet proprietary geospatial vector data format for geographic information system (GIS) software for storing elevation data as a triangulated irregular network. It is developed and regulated by Esri, US. The Esri TIN format can spatially describe elevation information including breaking edge features. Each points and triangle can carry a tag information. A TIN stored in this file format can have any shape, cover multiple regions and contain holes.
The Harvard Laboratory for Computer Graphics and Spatial Analysis pioneered early cartographic and architectural computer applications that led to integrated geographic information systems (GIS). Some of the Laboratory's influential programs included SYMAP, SYMVU, GRID, CALFORM, and POLYVRT. The Laboratory's Odyssey project created a geographic information system that served as a milestone in the development of integrated mapping systems. The Laboratory influenced numerous computer graphic, mapping and architectural systems such as Intergraph, Computervision, and Esri.
A Geodatabase is a proprietary GIS file format developed in the late 1990s by Esri to represent, store, and organize spatial datasets within a geographic information system. A geodatabase is both a logical data model and the physical implementation of that logical model in several proprietary file formats released during the 2000s. The geodatabase design is based on the spatial database model for storing spatial data in relational and object-relational databases. Given the dominance of Esri in the GIS industry, the term "geodatabase" is used by some as a generic trademark for any spatial database, regardless of platform or design.
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