2. Introduction To Gis (geographical Information System)

Introduction to GIS (Geographical Information System)

What Is a GIS? A geographic information system (GIS) is a computer-based tool for mapping and analyzing things that exist and events that happen on earth.  GIS technology integrates common database operations such as query and statistical analysis with the unique visualization and geographic analysis benefits offered by maps. 

GIS Definition Burrough (1986) defines GIS as “a set of tools for collecting, storing, retrieving at will, transforming and displaying spatial data from the real world for a particular set of purposes”  Aronoff (1989) gives a. general description of GIS as “any manual or computer-based set of procedures used to store and manipulate geographically-referenced data.” More specifically, Aronoff (1989) defines GIS as a computer-based system that provides four sets of capabilities to handle georeferenced Data: 1. Data input 2.Data management (Data Storage and Retrieval), 3. Manipulation and analysis, 4. Data Output 

The major challenges we face in the world today-overpopulation, pollution, deforestation, natural disasters--have a critical geographic dimension.

Gis Concept

Evolution of GIS Revolution in information technology  Computer Technology  Remote Sensing  Global Positioning System (GPS)  Communication Technology Rapidly declining cost of computer hardware Enhanced Functionality of software

Why GIS? 

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70% of the information includes some geographical Facts in the decisionmaking process Ability to assimilate divergent sources of data both spatial and non-spatial (attribute data) Visualization impact Sharing of information Analytical capability in a spatial context

Spatial Operations Many computer programs can handle geographic data such as those described below 1. Spreadsheets (e.g., lotus 1 -2-3, QuatroPro). 2. Database Management Systems (e.g., Oracle, dBase) 3. Computer Aided Design (e.g., AutoCad) 4. Cartographic packages (e.g. Aldus Freehand, CarthoGraphix) 5. Photogrammetrical software (e.g. DMS) 6. Image Processing Software (e.g., ERDAS)

Geometry and attributes of Spatial objects

Points, Its ID and Attributes Lines, Its IDs and Attributes Polygons, Its IDs and Attibutes

What Can GIS Do for You? 

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Perform Geographic Queries and Analysis Improve Organizational Integration Make Better Decisions Making Maps

Component of GIS Hardware Software Database People (Users) Methods (Policy and Procedures

How GIS Works ? 1. 2.

Geographic References Vector and Raster Models

GIS Tasks  Input  Manipulation  Management  Query

and Analysis  Visualization

Proximity Analysis Overlay Analysis

Data for GIS  What

Map Data Do I Need?

– Base Maps – Business Maps and Data – Environmental Maps and Data – General Reference Maps

How Do I Get Map Data? 

Methods In Nepal – – –

Existing maps Field Survey Digital data available in Departments of Survey, Min Bhawan, Kathmandu, Nepal – ICIMOD