Key aspects of GIS
Key aspects of GIS

A geographic information system (GIS) is a system used to describe and characterize the earth and other geographies for the purpose of visualizing and analyzing geographically referenced information.

Many have characterized GIS as one of the most powerful of all information technologies because it focuses on integrating knowledge from multiple sources (for example, as layers within a map) and creates a crosscutting environment for collaboration. In addition, GIS is attractive to most people who encounter it because it is both intuitive and cognitive. It combines a powerful visualization environment—using maps to communicate and visualize—with a strong analytic and modeling framework that is rooted in the science of geography.

This combination has resulted in a technology that is science based, trusted, and easily communicated using maps and other geographic views.

ArcGIS combines series of fundamental aspects of GIS:

A GIS utilizes a layer-based geographic information model for characterizing and describing our world.

ArcGIS models geographic information as a logical set of layers or themes. For example, a GIS can contain data layers for the following:

  • Streets represented as centerlines
  • Land-use areas that represent vegetation, residential areas, business zones, and so forth
  • Administrative areas
  • Water bodies and rivers
  • Parcel polygons representing landownership
  • A surface used to represent elevation and terrain
  • An aerial photo or satellite image for an area of interest
GIS models geographic information as layers.

Geographic information layers such as those described here are represented using a few common GIS data structures:

  • Feature classes: Each feature class is a logical collection of features of a common type (such as the four feature types shown here).
Types of features
  • Raster datasets: Rasters are cell-based datasets used to hold imagery, digital elevation models, and other thematic data.
Imagery and raster data
  • Attributes and descriptive information: These are traditional tabular information used to describe features and categories about the geographic objects within each dataset.
Attribute tables

Like map layers, GIS datasets are geographically referenced so that they overlay one another and can be located on the earth's surface.

See Overview of geographic information elements for more information about modeling and representing geographic information.

A GIS uses maps to visualize and work with geographic information.

Each GIS includes a set of intelligent, interactive maps and other views (such as 3D globes) that show features and feature relationships on the earth's surface. Various map views of the underlying geographic information can be constructed and used as "windows into the geographic database" to support query, analysis, and editing of geographic information. Maps can also be used to access geographic modeling tools that are used to derive new information.

Examples of 2D and 3D maps

GIS maps are interactive and help to communicate vast amounts of information. You can reach "through" an interactive map to present any set of information that helps your end users meet their missions and do important work.

See How maps convey geographic information for more information about mapping and visualization.

A GIS has a comprehensive set of analytic and data transformation tools to perform spatial analysis and data processing.

GIS includes a large set of geoprocessing functions to take information from existing datasets, apply analytic functions, and write results into new result datasets. There are numerous spatial operators, such as the Buffer and Intersect tools shown here, that can be applied to GIS data.

Example use of the Buffer and Intersect tools

Each geoprocessing tool takes existing information as input and derives a new result, which can be used in subsequent operations. This ability to string together a logical sequence of operations so that you can perform spatial analysis and automate data processing—all by assembling a model—is one of the key elements of GIS.

Source: http://help.arcgis.com