Data is raw form of information, which is given to the computer for processing. However, database is an organized collection of related data. Database should be integrated, structured and shared.
So here we can say that GIS is both a database system with specific capabilities for spatially referenced data as well as a set of operations for working with the data.
GIS database consist of sets of information called Layers. Each layer represents a particular type/class of geographic data. For example, one layer may include information on the road network in an area as line layer.
The GIS can combine these layers into one image, showing how the road network, land use, soil, and elevation relate to one another. Engineers/ Scientists might use this image to determine areas with more urban growth/ urban sprawl, loss of agriculture land etc. GIS can help to answer several questions for any application such as:
·Location: What exists at a particular location?
· Condition: Identify locations where certain conditions exist.
· Trends: What has changed since?
· Patterns: What spatial patterns exist?
· Modeling: What happens if…?
Primarily GIS uses two main types of data – geographically referenced data/geospatial data as well as non-spatial/attribute data.
Spatial data: It represents geographic features (Location and shape) associated with the real world locations and their relationship to other features. It is a mappable data.
Geographical features are depicted on map by point, line and polygon. For example, spatial data about various cities may be recorded in terms of their latitude and longitude, or (X,Y) with known origin.
· Point Feature: A discrete location depicted by a special symbol. A single x, y co-ordinates.
· Line Feature: It is a linear feature. A set of ordered x, y co-ordinates.
· Polygon feature: An area feature, where boundary encloses a homogeneous area.
Non-spatial data: It is known as attributes. It is the descriptive information about the characteristics of the feature. Attributes are stored as a set of numbers and characters in the form of a table. For example,
Property ID (Integral value),
Year of its establishment (Date/Time),
Property value (Floating point number),
Property’s Owner Name (string) etc.
Many attribute data files can be linked together through the use of common identifier code.
Combined spatial data and associated non-spatial data are termed as “Geographic Data or Geo-spatial Data”. Geographic data are the raw materials from which GIS users create the information needed to make decisions.
Geo-spatial data uses different feature types (raster and vector) to uniquely identify the location and their entities that exist on the earth surface. Geographic data are a significant subset of spatial data, although the terms geographic, spatial and geo-spatial are often used interchangeably.
Geo-spatial Data is crucial to any implementation of GIS. This data must be properly organized (structured) in digital format so as to store and manage the same.