GEOGRAPHIC INFORMATION SYSTEM

INTRODUCTION

A geographic information system (GIS) is a system for capturing, storing, analysing and managing data, information and associated attributes which are spatially referenced to the Earth. It is an information system capable of integrating, storing, editing, analysing, sharing and displaying geographically referenced information. It is also a tool that allows users to create interactive querries or searches, analyse the spatial information, edit data, maps and present the results of all these informations.

Geographic information system technology can be used for scientific investigations, resource management, asset management, environmental impact assessment, urban planning, cartography, criminology, history, sales, marketing and logistics.

TECHNIQUES USED IN GIS

Data Creation :

Modern GIS technologies use digital information for which various digitized data creation methods are used. The most common method of data creation is digitization. With the wide availability of ortho-rectified imagery (both from satellite and aerial sources), heads-up digitizing is becoming the main avenue through which geographic data is extracted.

Relating Information From Different Sources :

The primary requirement for the source data consists of knowing the locations for the variables. Any variable that can be located spatially can be fed into a GIS. Different kinds of data in map form can be entered into a GIS. A GIS can also convert existing digital information which may not yet be in map form into forms it can recognise and use.

Data Representation :

GIS data represents real world objects (roads, land use, elevation) with digital data. Real world objects can be divided into two (2) abstractions i.e. discrete objects and continuous fields. There are two (2) broad methods used to store data in a GIS for both abstractions i.e. raster and vector.

Data Capture :

Data capture i.e. entering information into the system consumes much of the time of GIS practitioners. There are variety of methods used to enter data into a GIS such as existing data printed on paper can be digitized or scanned to produce digital data to enter into GIS, survey intruments and several other survey tools such as GPS can also be diractly entered into GIS, remotely sensed data, satellite remote sensing and etc.

Projections, Coordinate Systems and Registration :

Map information in a GIS must be manipulated so that it registers or fits with information gathered from other maps. Before the digital data can be analysed, they may have to undergo other manipulations - projection and coordinate conversions e.g. that integrate them into GIS.

Spatial Analysis With GIS :

Several methods or model for spatial analysis with GIS such as data modeling, topological modeling, networks, cartographic modeling, map overlay, automated cartography, geostatistics, address geocoding and reverse geocoding.

Spatial ETL :

Spatial ETL tools provide the data processing functionality of traditional Extract, Transform, Load (ETL) software but with a primary focus on the ability to manage spatial data. They provide GIS users with the ability to translate data between different standards and proprietary formats whilst geomatricallty transforming the dat en-route.

GIS SOFTWARE

Geographic information can be assessed, transferred, transformed, overlaid, processed and displayed using numerous software applications. Within industry commercial offerings from companies such as ESRI and Mapinfo dominate, offering an entire suite tools. Government and military departments often use custom software, open source products such as GRASS or more specialised products that meet a well defined need.

Although free tools exist to view GIS datasets, public access to geographic information is dominated by online resources such as Google Earth and interactive web mapping.

Data Creation :

GIS processing software is used for the task of preparing data for use within a GIS.

Geodatabases :

A geodatabases is a databse with extensions for storing, querying and manipulating geographic information and spatial data.

Management and Analysis :

GIS analysis software takes GIS data and overlays or otherwise combines it so that the data can be visually analysed. It can output a detailed map, image or movie used to communicate an idea or concept with respect to a region of interest.

Statistical :

GIS statistical software uses standard database querries to retrieve and analyse data for decision making.

Readers :

GIS readers are computer applications that are designed to allow users easily view maps as well as view and query GIS managed data.

Web API :

GIS API's are designed to manage GIS data for its delivery to a web browser client from a GIS server.

Mobile GIS :

GIS has seen many implementations on mobile devices. With the widespread adoption of GPS, GIS has been used to capture and integrate data in the field.

Free and Open Source GIS Software :

Many GIS tasks can be accomplished with free or open source software. Well known open source GIS software includes GRASS GIS, Quantum GIS, Map Server, uDig, OpenJUMP, gvSIG and many others.

Vehicle Navigation :

A database model of a network of roads and related features is a form of GIS data that is used for vehicle navigations systems.

CONCLUSIONS

Many disciplines can benefit from GIS technology. An active GIS market has resulted in lower costs and continual improvements in the hardware and software componants of GIS. These developments will, in turn result in a much wider use of the technology throughout science, government, business and industry, with applications including real estate, public health, crime mapping, national defense, sustainale development, natural resources, landscape architecture, archeology, regional and community planning, transportation and logistics.

GIS is also diverging into location based services (LBS) and LBS allows GPS enabled mobile devices to display their location in relation to fixed assets such as nearest gas station, mobile assets such as friends or to relay their position back to a central server for display or other processing. These services continue to develop with the increased integration of GPS functionality with increasingly powerful mobile electronics such as cell phones, PDAs and laptops.