Who knows what gis is?
Geographic Information System (GIS) is a computer-based tool, which can draw and analyze things and events existing on the earth. GIS technology combines the unique visualization effect and geographical analysis function of maps with general database operations (such as query and statistical analysis). This ability makes GIS different from other information systems, which makes it of practical value in explaining events, predicting results and planning strategies of various public and individual enterprises and institutions.
The main challenges facing the world today are overpopulation, environmental pollution, forest destruction, natural diseases and so on. These are all related to geographical factors.
Whether engaging in a new occupation, finding the most suitable soil for planting bananas or calculating the best driving route for ambulances, these local problems also have geographical factors.
Map making and geographic analysis are not new, but GIS can accomplish these tasks better and faster than traditional manual methods. Moreover, before the emergence of GIS technology, only a few people had the ability to use geographic information to help make decisions and solve problems.
Today, GIS is a global industry with hundreds of thousands of people and billions of dollars. GIS courses are offered in middle schools, colleges and universities all over the world. Experts in every field are constantly aware of the advantages of thinking and working from a geographical perspective.
(b) Introduction to Geographic Information System-Composition of Geographic Information System
GIS consists of five main elements: hardware, software, data, personnel and methods.
Hard part
The hardware is a computer operated by GIS. Today, GIS software can run on many types of hardware. From central computer server to desktop computer, from stand-alone computer to network environment.
Soft part
GIS software provides the functions and tools needed to store, analyze and display geographic information. The main software components include:
Tools for inputting and processing geographic information
Database Management System (DBMS)
Tools to support geographic query, analysis and visualization
The graphical interface (GUI) of these tools is easy to use.
data
The most important part of GIS system is data. Geographic data and related tabular data can be collected by themselves or purchased from commercial data providers. GIS integrates spatial data with data from other data sources, and can manage spatial data by using the database management system that most companies use to organize and save data.
personnel department
If no one manages the GIS system and makes plans to apply it to practical problems, then GIS technology will be of little value. The users of GIS range from technical experts who design and maintain the system to people who use the system and complete their daily work.
Square method
A successful GIS system has a good design scheme and its own business rules, which are standardized and unique for every company.
(3) Introduction of Geographic Information System-How does Geographic Information System work?
GIS is used to store information about the world. It is a collection of all subject layers that can be connected together through geographical relations. This simple but very powerful and universal concept plays an inestimable role in solving many practical problems, including tracking transmission tools, recording detailed information of the plan, simulating global atmospheric circulation and so on.
Geographic reference system
Geographic information contains a clear geographic reference system, such as latitude and longitude coordinates or national grid coordinates. It can also include indirect geographic reference systems, such as address, postal code, census area name, forest location identification, road name, etc. An automatic processing system called geocoding is used to change from an indirect reference system (such as address description) to an explicit geographic reference system (such as multiple positioning). These geo-reference systems can help you locate certain elements, such as business activities and forest locations, and also locate certain events, such as earthquakes, for surface analysis.
Vector and raster mode
Geographic information system works in two different basic geographic modes-vector mode and grid mode.
In vector mode, information about points, lines and polygons is encoded and stored in the form of X and Y coordinates. The position of point features (such as drilling holes) can be described by an X and Y coordinate. Line features such as roads and rivers can be stored in a series of point coordinates. Polygonal features, such as sales areas or river collection areas, can be stored in a closed-loop coordinate system. Vector model is very helpful for describing some discrete features, but it is not very useful for continuously changing features, such as soil type or the cost of going to the hospital.
The grid pattern develops into a pattern of continuous features. Raster images contain grid cells, a bit like scanned maps or photos. Vector mode and raster mode have their own advantages and disadvantages when storing geographic data. Modern GIS can handle these two modes.
(4) Brief introduction of geographic information system-the task of geographic information system
Generally speaking, GIS has the following five processes or tasks:
invest
deal with
operate
Query and analysis
visualize
invest
Before geographic data can be used in GIS, it must be converted into an appropriate digital format. The process of converting drawing data into computer files is called digitalization. For large-scale projects, modern GIS technology can fully automate this process through scanning technology, while for smaller projects, it needs to be digitized manually (using digital desks).
At present, many geographic data are already in data formats compatible with GIS. These data can be obtained from data providers and directly loaded into GIS.
deal with
For special GIS projects, it may be necessary to convert or process the data into some form to suit your system. For example, geographic information is suitable for different scales (the street centerline file scale may be1:100000; The population boundary is1:50,000; The postal code is 1: 10000). This information must be converted to the same scale before it can be integrated. This can be a temporary conversion for display purposes or a permanent conversion for analysis. GIS technology provides many tools to process spatial data and delete unnecessary data.
operate
For small GIS projects, it is enough to store geographic information as a simple file. However, when there is a large amount of data and a large number of data users, it is best to use a database management system (DBMS) to help store, organize and manage the data. Database management system DBMS is a computer software used to manage a database, which is a complete data set.
There are many different DBMS designs, but in GIS, the design of relational database management system is the most useful. In the design of relational database system, conceptually, data is stored in a series of tables. * * * Fields in different tables can connect them. This surprisingly simple design is widely used, mainly because of its flexibility and being widely used with or without GIS.
Query and analysis
Once you have a multifunctional GIS system that contains your geographic information, you may start to ask some simple questions, as follows:
Who owns the land in this corner?
How far is the distance between the two places?
Where is the boundary of industrial land?
Questions about analysis may be:
Where are the suitable places to build a new house?
What is the best soil type for planting oak trees?
If I want to build a expressway here, what impact will it have on traffic?
GIS provides simple mouse click query function and complex analysis tools to provide timely information for managers and similar analysts. When you analyze geographic data to find patterns and trends, or put forward the idea of "what if ...", you are actually using GIS technology. Modern GIS has many powerful analysis tools, but two of them are particularly important.
1. Proximity analysis
How many houses are there around this water area 100 meter?
How many consumers are there in this store 10 km?
What area does alfalfa occupy within 500 meters around this well?
In order to answer these questions, GIS technology uses a processing method called buffering to determine the close relationship between elements.
2. Coverage analysis
The integration method of different data layers is called superposition. In short, it can be a visualization operation, but an analysis operation requires one or more physically connected data layers. Overlay or spatial connection can combine tax data with land, slopes, vegetation or landowners.
visualize
For many types of geographic operations, the final result is best displayed as a map or chart. Maps are very effective for storing and transmitting geographic information. Cartographers have been making maps for thousands of years, and GIS provides a brand-new and exciting tool for expanding this cartographic art and science. Map display can be integrated into reports, three-dimensional observation, photos and images, multimedia and other outputs.
(5) Introduction of related technologies of geographic information system.
GIS is closely related to several other information systems, but it is different from other information systems because of its ability to process and analyze geographic data. Although there are no hard and fast rules to classify these information systems, the following discussion is helpful to distinguish GIS from desktop mapping, computer-aided design CAD, remote sensing, DBMS and GPS technology.
Desktop drawing
Desktop mapping systems use maps to organize data and user interaction. The main purpose of this system is to generate maps: maps are databases. Most desktop mapping systems only have limited functions of data management, spatial analysis and personalization. Desktop drawing system runs on desktop computers, such as PC, Macintosh and small UNIX workstations.
Computer aided design
Computer aided design (CAD) system promotes the design and planning of architecture and capital construction. This design requires assembling parts with inherent characteristics to produce the whole structure. These systems need some rules to indicate how to assemble these components, and they have very limited analysis ability. CAD system has been extended to support map design, but tools for managing and analyzing large-scale geographic databases are limited.
Remote sensing and global positioning system
Remote sensing is a science and technology that uses sensors to measure the earth, such as cameras on airplanes, global positioning system (GPS) receivers or other equipment. These sensors collect data in the form of images and provide special functions for using, analyzing and visualizing these images. Because it lacks powerful geographic data management and analysis functions, it can't be called a real GIS.
DBMS database management system
Database management system specializes in how to store and manage all kinds of data, including geographic data. DBMS optimizes data storage and search, and many GIS rely on it to achieve this goal. Compared with GIS, they have no tools for analysis and visualization.
(6) Introduction to GIS-What can GIS do?
Conduct geographic information query and analysis.
The ability of GIS to search databases and query geographic information has saved millions of dollars for many companies. GIS can:
Shorten the time to respond to customer requirements.
Looking for land suitable for development
Find out the relationship between grain, soil and weather.
Circuit fault location
Real estate agents can use GIS to find all the houses that meet the following conditions in a certain area: a tile roof and five rooms, and list all their characteristics.
You can further refine the query by adding conditions: the house price must be less than $0/00 per square foot/kloc. You can also list these houses within a certain distance from the school.
Improve mechanism integration
Many institutions that have adopted GIS have found that one of their main benefits is to improve their own institutions and resource management. Because GIS has the ability to link data sets and geographic information, it enables them to share and exchange local information. By creating an enjoyable database, one department can benefit from the work of another department, because the data only needs to be collected once, but it needs to be used many times.
With more and more communication between individuals and departments, redundancy is reduced, productivity is improved, and the efficiency of the whole organization is also improved. Therefore, in an effective company, users and infrastructure databases can be integrated together, so that when maintenance is needed, the affected users will get letters from the computer.
Make a wise decision
An old adage "Good information leads to good decisions" is correct for GIS and other information systems. However, Geographic Information System (GIS) is not an automatic decision-making system, but a map data tool for query, analysis and decision support. GIS technology has been used to help complete some tasks, such as providing information for planned surveys, helping to solve territorial disputes, and setting up road signs under the principle of minimizing visual interference.
You can use GIS to help you choose a new house location, so that it is least affected by the environment, in a low-risk area and close to the population gathering place. This information can be provided concisely in the form of maps and additional reports, so that decision makers can concentrate on solving practical problems instead of spending time understanding the data. Because GIS results can be obtained quickly, multiple hypothetical results can be evaluated efficiently.
charting
Maps play an important role in geographic information system. The drawing method of GIS is much more flexible than the traditional manual or automatic drawing method. She started to create a database. Existing paper maps can be digitized, and information compatible with computers can be converted into geographic information systems. The graphic database based on GIS can be extended and its scale is not limited. The map can be centered anywhere in any proportion, and the selected information can be effectively displayed by using special characters, with outstanding effect.
The characteristics of atlas and map series can be coded by computer programs and compared with the final database products. Digital products used in other GIS can also come from a simple copy of the database. In large organizations, terrain database can be used as a reference framework for other departments.