Spatial data capture and edition goes hand in hand with GIS database creation. Sometime, or many a times, the database is designed long before data capture

Database is a large, computerized collection of structured data. In non-spatial domain, databases have been used since 1960s in bank account administration, stock monitoring, salary administration, stores management, flight reservations etc.

Designing a database is not an easy task. One has to consider the purpose, available data sources and formats before data can be entered into the database. The format means data structure. Database should be properly maintained and up-to-date.

Database Management Systems (DBMS) are a software package that allows the user to set up, use and maintain a database.

GIS have inbuilt Ms Access for small databases, but has ArcSDE for large databases. GIS stores data mainly in relational database discussed above

Reasons for Database

  • DBMS supports storage and maintenance of very large volume of datasets
  • DBMS can be instruevcted to guard over data correctness or valididity
  • DBMS supports concurrent use of the same dataset for many users
  • Provides high level declarative query language. A query is is a computer programme that exctracts data from the database based on specified condition
  • A DBMS supports use of data A data model is language which can apply to define data structure and in data manipulation and storage
  • Include data backup and recovery functions
  • Allows control over data redundancy

Relational Data Model

A data model is a language that allows: The data structures to be stored; the integrity constraints, and the computer programmer to manipulate the data

For relational data model, the structure used to define the database is attributes, tuples and relations. Computer program can exctract information applying quely and change content (update)

In relational data model, a database is view as a collection of relations, commonly known as tables. A table or a relation is a collection of tuples or records. An attribute is a named field of tuple. Same attribute comes from single domain (text/string, integer, real, date, etc)

When creating a relation is created, we need to indicate the type of tuple to store:

  • Provide name of relation
  • Indicate name of attributes
  • Set domain for each attribute

Undelaying the attribute and their domain indicate primary key of the relations The set of tuples in a relation at a given point is called a relation stance Linking GIS and database.

GIS software provide support for spatial data and attribute data. GIS stores spatial and attribute data separately, thus, it links them through a primary key.