Introduction and Types of GIS Data: Spatial and Attribute Data (Especially for GATE-Geospatial 2022)

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Georelational data model links spatial data and attribute data by id. Attribute data stored in feature attribute table which contains the id. Row is called a record; column is called a field or an item.

Types of GIS Data

A database or tabular file containing information about a set of geographic features, usually arranged so that each row represents a feature and each column represents one feature attribute. There are Two types of attribute tables:

  • Spatial feature attribute table
  • Non-spatial, table does not have direct access to feature geometries
Attribute Table

Linking Attribute Data and Spatial Data

The georelational data model store spatial data and attribute data in separate files. Each map feature has unique label ID. Linked by feature ID, the two sets of data files can be queries, analyzed, and displayed. Attribute data are stored in a table called feature attribute table.

Linked Spatial and Attribute Data

Attribute data are stored in tables. Each row of a table represents a map feature. Each column represents a characteristic. The object-oriented data model stores both data in a single database, but can distinguish spatial data from attribute data.

Intersection of a row and a column shows value of a characteristic for a feature.

Intersection of a Row and Column

Above figure, a feature attribute table consists of rows and columns. Each row represents a spatial feature, and each column represents a property or characteristic of the spatial feature.

As above example, most GIS projects have many attributes. To store all attributes in a single table is not efficient both time and computer space and difficult to use and update.

A database management (DBMS) system provides tools for data input, search, retrieval, manipulation, and output to manage, integrate and share the database.

Database Management

A database management system (DBMS) is system software for creating and managing databases. The DBMS provides users and programmers with a systematic way to create, retrieve, update, and manage data.

The DBMS manages three important things: the data, the database engine that allows data to be accessed, locked, and modified- and the database schema, which defines the database՚s logical structure.

The DBMS can offer both logical and physical data independence. That means it can protect users and applications from needing to know where data is stored or having to be concerned about changes to the physical structure of data

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