1. WHAT IS GIS ? Geographical Information System- GIS is a computer tool to create map and analyze things, phenomenon on the world. GIS technology combines typical database operations (as inquiry structure) and statistical analysis, geographical analysis, among them geographic analysis and image is provided only from maps. These possibilities distinct GIS with other information systems and make GIS have a wide range of applications in many different fields (analysis of the events, anticipating impact and planning strategic). Currently, the main challenges we face - the population explosion, pollution, deforestation, natural disasters occupy an importance geographic space.
When determining a new business (as well find a property for growing bananas, or calculate the optimal route to an emergency vehicle trips), GIS allows to create map, and coordinate information, an overview scenarios, solving complex problems, and develop effective solutions that previously were not achieved. GIS is a tool for individuals, organizations, schools, government and businesses to use new methods solving the problems. Mapping and geographic analysis are not a new technology, but GIS execute this work better and faster than the old manual method. Before GIS technology, only a few people have necessary skills to use geographic information to help solving problems and making decisions.
Today, GIS is a billions of dollars industry with the participation of hundreds of thousands of people around the world. GIS is taught in schools, universities around the world. Experts from all fields are aware of the advantages of the combination of their work and GIS.
2. COMPONENTS OF GIS? DBMS (Database Management System):
GIS is combined by five main components: hardware, software, data, human and methods.
Hardware: Hardware is a computer system on which a GIS operates. Today, GIS software can run on many types of hardware, from a central server to workstations operate independently or network link.
Software: GIS software provides necessary functions and tools to store, analyze and display geographic information. The main components of GIS software are:
+ Data input tools and operations on geographic
+ Database Management System (DBMS)
+ Inquiry support tools, analyze and display
+ Graphical User Interface (GUI) to access the tools easily
Data: Data can be considered the most important component in a GIS. The geographic data and related attribute data can be collected by user or purchase from commercial data provider. GIS system will combine spatial data with other data sources, can even use the DBMS to store and organize data management.
Human: GIS technology will be limited if there are not human participating in managing system and developing of GIS applications in practice. GIS users can be the technical experts who design and maintain systems, or who use GIS to solve problems in work.
Method: One GIS is successful in design and Business law when it is simulated and execute uniquely for each organization
3. HOW GIS WORKS?
GIS stores information about the real world as a set of thematic layers that can be linked together through geographic features. This is simple but extremely important and is a versatile tool that has been proven very valuable in solving practical problems, from established distribution routes of the car trip, to make a detail report for planning applications, or simulate the global atmospheric circulation.
Geographic reference: The geographic information contain the reality geographic reference (such as longitude, latitude or national coordinates), or contain hidden geographic reference (such as addresses, ZIP code, the identifiable areas name definition set of forest or street). Geographic encryption is the automatic process which is commonly used to generate the reality geographic references (multiple locations) from the hidden geographic reference(as the descriptions, such as addresses). The geographic reference for positioning objects (such as forests or business location information) and events (like earthquakes) on the surface of the earth for the purpose of analysis.
Vector and Raster Models: Geographic information system works with two types of geographic data model which are fundamentally different - the model vector and raster models. In the vector model, information about points, lines and regions are encoded and stored as a set of coordinates x, y. Position of the point objects , such as boreholes, can be represented by a single coordinate of x, y. Objects as lines, such as roads, rivers and streams, can be saved as a set of point coordinates. As the object, such as regional trade areas or watersheds, are stored as a closed ring of the point coordinates.
Vector model is useful for the description of individual objects, but less effective in describing the objects that transform continuously as soil or estimated cost for hospital. Raster model was developed to simulate continuous objects like these. A raster image is a set of grid cells. Both vector and raster models are used to store geographic data with the advantages, disadvantages, the modern GIS systems are capable of managing both of these models.
4. TASKS OF GIS.
General purposes of the geographic information system is executing these six following tasks:
+ Input data
+ Data manipulation
+ Data management
+ Q & A and analysis
Input data: Before geographic data can be used for GIS, this data must be converted to the appropriate digital type. The process of transferring data from paper maps into digital data files is called digitizing process.
Modern GIS technology can make this process fully automatic with picture scanning technology for large objects; smaller objects require a process of manual digitizing (using digitizing table). Today, many types of geographic data are really compatible with GIS formats. These data can be obtained from suppliers and entered data directly into GIS.
Data manipulation: There are some cases that data formats require to be changed format and manipulate with some way to compatible with one given system. For example, geographic information has different represent values at different scales (Street systems are represented in detail in traffic files, but less detailed in census file and have ZIP code in area level). Before these information are combined together, they must be changed into one scale (accurate level or necessary level). This can be a temporary format changing for displaying purpose or fixed for analysis requirement. GIS technology supplies many tools for manipulations on space data and allow to delete unnecessary data.
Data Management: For small GIS projects, we can save the geographic information as simple files. However, when data size becomes larger and the number of users becomes bigger, the best way is to use the database management system (DBMS) to assist in storing, organizing and managing information. A DBMS is simply a software for managing database.
There are many different DBMS structures, but in GIS , relationship structure proved to be the most effective. In relationship structure, the data are stored in form of tables. General attributes fields in different tables are used to link these tables together. Because of flexible structure, this simple structure is used and widely deployed in applications both inside and outside the GIS.
Q&A and analysis: Once we have GIS storage the geographic information, we can begin to ask simple questions such as:
+ Who is owner of the land at street corners?
+ How far is it between 2 positions?
+ Where is the land for industrial activities?
Analysis questions such as:
+ Where are all the appropriate locations for the construction of new buildings?
+ What is the type of better soil for oak forest?
+ If you build a new highway here, how will traffic be affected?
GIS provides the ability to answer simple questions "point out and click" and the sophisticated analysis tools to provide timely information for the managers and analysts. Modern GIS systems have many effective analysis tools , including two special important tools:
+ Total number of customers in a radius of 10 km in area?
+ The land plot of about 60 m from the street surface?
To answer these questions, GIS use the buffer zone methods to determine adjacent relationships between objects.
Superposition analysis: Superposition is the process of integrating different information layers. Analysis operations requires one or more layers of data to be linked physically. ThisSuperposition or link space is probably a combination of data on soil, slope, vegetation or land property with tax valuation.
Display: With many operations on geographic data, the last result is shown the best as map or chart. Map is quite effective in keeping and exchanging geographic information. GIS provides many new and interesting tools to expand the art and science of the map industry. Display map can be combined with the report, three-dimensional images, photographs and other data (media)
5. DATA FOR GIS
Which map data is necessary? In general, there are some of popular types of map data as follows:
Base map: including maps of street, highway, road, administrative boundaries, boundaries of settlements; rivers, lakes; landmark border; names and raster maps.
Maps and trading data: including data related to population / demographic, consumer, business services, health insurance, real estate, media, advertising, business, transport, crime.
Maps and environment data : including data related to the environment, weather, environmental issues, satellite imagery, terrain and natural resources.
General Reference Map: world and nation map and national; data for particular database.
6. RELATED TECHNOLOGY
GIS is closely relate to some other information systems, but the ability to manipulate and analyze geographic data is implemented only on GIS technology. Although there is no canonical rule about classifying information systems, but below introduction will help to distinguish GIS with desktop mapping technologies, design with assistance by computer (computer-aided design - CAD ), remote sensing, database system management (DBMS), and global positioning system (GPS).
Desktop Mapping: A desktop mapping system uses maps to organize data and user interaction. The focus of this system is a mapping: map is the database. Most Desktop Mapping systems are limited than the ability to manage GIS data, spatial analysis and the ability to customize. Desktop mapping systems operate on desktop computers such as PC, Macintosh, and small UNIX workstations.
CAD (computer-aided design - CAD ): CAD system support for the creation of design and construction of the infrastructure. This feature requires collecting fixed specific components to create the whole structure. CAD requires some rules of the collecting of components and analysis ability to analyze is very limited. CAD system can be extended to support maps but typically limited to managing and analyzing large geographic database.
Remote Sensing and GPS systems (Global Positioning System): Remote sensing is the science studying the Earth's surface using sensor techniques such as recording cameras from the aircraft, the GPS stations or other devices. These sensors collect data in images and provides the ability to manipulate, analyze and simulate these images. Due to lack of features to analyze and manage geographic data, so it cannot be called real GIS.
database management system specializing in storage and manage all types of data including geographic data. Many GIS systems used for the purpose of DBMS data storage. DBMS does not have the tools to analyze and simulate like GIS.