GIS DATABASE

Chapter 3 GIS Database • Data management

• Database definition and concept, • DBMS • Rows and columns table • Advantages of GIS database

Introduction  Geographic database are simply databases containing geographic data for a particular area and subject.  A geographic database is a critical part of an operational GIS both because of the cost of creation and maintenance, and because of the impact of a geographic database on all analysis, modelling, and decision-making activities.  Databases can be physically stored in files or by using specialist software programs called DBMS.

 today., most large organizations use a combination of files and DBMS for storing data assets.

Data Management  data management functions necessary in any GIS system to facilitate the storage, organization, and retrieval the data - database  In GIS, database was created to manage a large proportion of data  Database is a set of structured data or collection of related data  DBMS – organized data in computer database

Database definition and concept Definition:  A database can be thought of a set of data on a particular subject

 A database is an organized collection of data. It is the collection of tables, queries, reports, views and other objects. The data is typically organized to model aspects of reality in a way that supports processes requiring information.  A geographic database are simply a database geographic data for a particular area or subject.

containing

A database is just what the name implies, a base collection of data. The data is organized in some manner so that the information contained within the database can be easily retrieved. As data processing has become more sophisticated, so have methods for collecting, storing and retrieving information. Databases have become the cornerstone for an overwhelming amount of the computing environment in existence.

A geographic database is a critical part of operational GIS because

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Cost of creation & maintenance

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The impact of geographic database on all analysis, modelling & decision making activities.

The Database Approach ď‚´ The GIS database approach is a simple concept with two basic aspects.

1. recognition that the database is central to GIS projects and to organizations using GIS. 2 - much of the data processing and analytical operations take place in the database when possible.

 a database is a collection of non-redundant data which can be shared by different application systems  stresses the importance of multiple applications, data sharing  the spatial database becomes a common resource for an agency  implies separation of physical storage from use of the data by an application program, i.e. program/data independence  the user or programmer or application specialist need not know the details of how the data are stored  such details are "transparent to the user"  changes can be made to data without affecting other components of the system. e.g.  change format of data items (real to integer, arithmetic operations)  change file structure (reorganize data internally or change mode of access)  relocate from one device to another, e.g. from optical to magnetic storage, from tape to disk

The Database in GIS  The central data integrator for GIS is the database.  Database in GIS is a simple concept - a list or table of data arranged as rows and columns.  Rows are the records, or each observation entered into the database.  Columns are called fields, which present the attributes or descriptions of each record.

Rows and columns table  Tabular information is the basis of geographic features, allowing you to visualize, query, and analyze your data.  In the simplest terms, tables are made up of rows and columns, and all rows have the same columns. In ArcGIS, rows are known as records and columns are fields.  Each field can store a specific type of data, such as a number, date, or piece of text.

Sample of database created in GIS system

Rows and columns table

DATABASE MANAGEMENT SYSTEM (DBMS) A DBMS is a software application designed to organized the efficient and effective storage and access of data.

A DBMS successful because : Able to provide data model – a mechanism used to represent the real world object digitally in a computer system

 A data load capabilities – provide tools to load data into database  Indices – data structured used to speed up searching  Query language – support standard data query  Controlled updates – updating activities are controlled – to ensure effective data storage  Backup and recovery – valuable data are protected from system failure and incorrect update

Database Management System (DBMS) •

The data in a computer database are managed and accessed through a DBMS.

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Ex:

Database DBMS

Hotel booking

Ski School booking

Travel arrangement

• DBMS as a computer program to control the storage, retrieval and modification of data (in a database) – Dale and Mclaughlin (1988) • DBMS will allow users to join, manipulate or otherwise access the data in any number of databases files. – Stern and Stern (1993) • A DBMS must allow the definition of data and their attributes and relationships, as well as providing security and an interface between the end users and their applications and the data itself.

• DBMS can be summarized: - file handling and file management (for creating, modifying or deleting the database structure) - adding, updating and deleting record - the extraction of information from data (sorting, summarizing and querying data) - maintenance of data security and integrity (housekeeping, logs, backup)

 The overall objective of a DBMS is to allow users to deal with data without needing to know how the data are physically stored and structured in the computer.  To achieved this, DBMS usually comprise software tools for structuring, relating, and querying data; tools for the design of data entry and report forms; and application generators for the creation of customized applications.  A DBMS manages data that are organized using a database data model.  This is analogous to the way in which spatial data are organized in a GIS according to a spatial data model (i.g Raster or Vector).

Database Data Models •

There are a number of different database data models. Amongst those that have been used for attribute data in GIS are the: – Hierarchical – Network – Relational – Object-relational – Object-oriented

Hierarchical Data Model ď‚´ The Hierarchical Data Model is a way of organizing a database with multiple one to many relationships. The structure is based on the rule that one parent can have many children but children are allowed only one parent.

Network Data Model ď‚´ The network model is a database model conceived as a flexible way of representing objects and their relationships. Its distinguishing feature is that the schema, viewed as a graph in which object types are nodes and relationship types are arcs, is not restricted to being a hierarchy.

Relational Data Model ď‚´ Relational data model is the primary data model, which is used widely around the world for data storage and processing. This model is simple and it has all the properties and capabilities required to process data with storage efficiency.

Object-relational Data Model ď‚´ The object-relational data model extends the relational model by providing system including object orientation and add constructs to relational query languages to deal with added (complex) data types, such extensions attempt to preserve the relational.

Object-oriented Data Model  A data model is a logic organization of the real world objects (entities), constraints on them, and the relationships among objects.  In the object oriented data model the both data and their relationship are contained in a single structure known us an object.  An object includes information about relationship between the facts within the object, as well as information about its relationship with other objects.

Creating Database ď‚´ Database design and implementation are guided by the relationships between the data to be stored in the database. ď‚´ The database design process is concerned with expressing these relationships, then implementation with setting up a new structure for these relationships within the chosen database software.

ď‚´ The stages of database creation are summarized:

Oxborrow (1989)

Reeve (1996)

Data investigation

Needs analysis

Data modelling

Logical design

Database design

Physical design testing

Database implementation

Implementation

Database monitoring

Maintenance

Data investigation: • Is the ‘fact finding’ stage of database creation.

• Here the task is to consider the type, quantity, and qualities of data to be included in the database. The nature of entities and attributes is decided.

Data modelling: • The process of forming a conceptual model of data by examining the relationships between entities and the characteristics of entities and attributes. This stage, like the data investigation stage, can be carried out independently of the software to be used.

Database design:

• The creation of a practical design for the database. • This will depend on the database software being used, and its data model.

This is the process of translating the logical design for the database (produced during the data modelling stage) into a design for the chosen DBMS. Field names, types, and structure are decided. In practice, the design will be a compromise to fit the database design model with the chosen DBMS.

Database implementation: • The procedure of populating the database with attribute data, and this is always followed by monitoring and upkeep, including fine tuning, modification and updating.

Advantages of GIS database  reduction in data redundancy - shared rather than independent databasesreduces problem of inconsistencies in stored information, e.g. different addresses in different departments for the same customer  maintenance of data integrity and quality  data are self-documented or self-descriptive - information on the meaning or interpretation of the data can be stored in the database, e.g. names of items, metadata  avoidance of inconsistencies - data must follow prescribed models, rules, standards  reduced cost of software development - many fundamental operations taken care of, however DBMS software can be expensive to install and maintain  Reduce maintenance cost – better data organization and reduce data duplication  security restrictions - database includes security tools to control access, particularly for writing

 Data transferred – user knowledge can be transferred between application easily - database remain constant  Improve data sharing – data can be provided to multilevel of users (manager, officer, public user, etc)  DBMS – better able to manage large number of data

DISADVANTAGES:  The cost of acquiring and maintaining DBMS software quite high

 DBMS add complexity of managing data especially in small project