What is a Geographic Information System (GIS)?
A geographic information system (GIS) is a computer system for capturing, storing, checking, and displaying data related to positions on Earth’s surface. By relating seemingly unrelated data, GIS can help individuals and organizations better understand spatial patterns and relationships.
GIS technology is a crucial part of spatial data infrastructure, which the White House defines as “the technology, policies, standards, human resources, and related activities necessary to acquire, process, distribute, use, maintain, and preserve spatial data.” GIS can use any information that includes location. The location can be expressed in many different ways, such as latitude and longitude, address, or ZIP code.
Many different types of information can be compared and contrasted using GIS. The system can include data about people, such as population, income, or education level. It can include information about the landscape, such as the location of streams, different kinds of vegetation, and different kinds of soil. It can include information about the sites of factories, farms, and schools, or storm drains, roads, and electric power lines.
With GIS technology, people can compare the locations of different things in order to discover how they relate to each other. For example, using GIS, a single map could include sites that produce pollution, such as factories, and sites that are sensitive to pollution, such as wetlands and rivers. Such a map would help people determine where water supplies are most at risk.
Data Formats .
GIS applications include both hardware and software systems. These applications may include cartographic data, photographic data, digital data, or data in spreadsheets.
Cartographic data are already in map form, and may include such information as the location of rivers, roads, hills, and valleys. Cartographic data may also include survey data and mapping information that can be directly entered into a GIS. Photographic interpretation is a major part of GIS.
Photo interpretation involves analyzing aerial photographs and assessing the features that appear.
Digital data can also be entered into GIS. An example of this kind of information is computer data collected by satellites that show land use—the location of farms, towns, and forests.
Remote sensing provides another tool that can be integrated into a GIS. Remote sensing includes imagery and other data collected from satellites, balloons, and drones.
Finally, GIS can also include data in table or spreadsheet form, such as population demographics. Demographics can range from age, income, and ethnicity to recent purchases and internet browsing preferences.
GIS technology allows all these different types of information, no matter their source or original format, to be overlaid on top of one another on a single map. GIS uses location as the key index variable to relate these seemingly unrelated data.
Putting information into GIS is called data capture. Data that are already in digital form, such as most tables and images taken by satellites, can simply be uploaded into GIS. Maps, however, must first be scanned, or converted to digital format.
The two major types of GIS file formats are raster and vector. Raster formats are grids of cells or pixels. Raster formats are useful for storing GIS data that vary, such as elevation or satellite imagery. Vector formats are polygons that use points (called nodes) and lines. Vector formats are useful for storing GIS data with firm borders, such as school districts or streets.
GIS technology can be used to display spatial relationships and linear networks. Spatial relationships may display topography, such as agricultural fields and streams. They may also display land-use patterns, such as the location of parks and housing complexes.
Linear networks, sometimes called geometric networks, are often represented by roads, rivers, and public utility grids in a GIS. A line on a map may indicate a road or highway. With GIS layers, however, that road may indicate the boundary of a school district, public park, or other demographic or land-use area. Using diverse data capture, the linear network of a river may be mapped on a GIS to indicate the stream flow of different tributaries.
GIS must make the information from all the various maps and sources align, so they fit together on the same scale. A scale is the relationship between the distance on a map and the actual distance on Earth.
Often, GIS must manipulate data because different maps have different projections. A projection is the method of transferring information from Earth’s curved surface to a flat piece of paper or computer screen. Different types of projections accomplish this task in different ways, but all result in some distortion. To transfer a curved, three-dimensional shape onto a flat surface inevitably requires stretching some parts and squeezing others.
A world map can show either the correct sizes of countries or their correct shapes, but it can’t do both. GIS takes data from maps that were made using different projections and combines them so all the information can be displayed using one common projection.
Once all the desired data have been entered into a GIS system, they can be combined to produce a wide variety of individual maps, depending on which data layers are included. One of the most common uses of GIS technology involves comparing natural features with human activity.
For instance, GIS maps can display what man-made features are near certain natural features, such as which homes and businesses are in areas prone to flooding.
GIS technology also allows users to “dig deep” in a specific area with many kinds of information. Maps of a single city or neighborhood can relate such information as average income, book sales, or voting patterns. Any GIS data layer can be added or subtracted to the same map.
GIS maps can be used to show information about numbers and density. For example, GIS can show how many doctors there are in a neighborhood compared with the area’s population.
With GIS technology, researchers can also look at change over time. They can use satellite data to study topics such as the advance and retreat of ice cover in polar regions, and how that coverage has changed through time. A police precinct might study changes in crime data to help determine where to assign officers.
One important use of time-based GIS technology involves creating time-lapse photography that shows processes occurring over large areas and long periods of time. For example, data showing the movement of fluid in ocean or air currents help scientists better understand how moisture and heat energy move around the globe.
GIS technology sometimes allows users to access further information about specific areas on a map. A person can point to a spot on a digital map to find other information stored in the GIS about that location. For example, a user might click on a school to find how many students are enrolled, how many students there are per teacher, or what sports facilities the school has.
GIS systems are often used to produce three-dimensional images. This is useful, for example, to geologists studying earthquake faults. GIS technology makes updating maps much easier than updating maps created manually. Updated data can simply be added to the existing GIS program. A new map can then be printed or displayed on screen. This skips the traditional process of drawing a map, which can be time-consuming and expensive.
Top 5 Benefits of Geographic Information Systems (GIS).
1. Asset management GIS allows you to see and sort the infrastructure and utilities that lie beneath a city’s streets, curbs and sidewalks. A typical utility map that shows sewer, water and storm infrastructure doesn’t have a lot of background information displayed other than pipe size and type. GIS maps have much more information tied to these utilities, like the age of material and past maintenance records. This makes it easier to track and manage that infrastructure. Asset management also helps you concretely track small details, like the exact location and frequency of water main breaks, making it a valuable tool in helping you assess your overall system.
2. Parcel management City officials and land owners generally have a handle on who owns which pieces of property, but exact boundaries sometimes aren’t adequately marked or clearly defined, particularly in smaller towns. GIS can create a geographically precise parcel map using legal documents and plats to correctly display ownership.
3. Better informed decisions Better access to information allows more informed decisions. Knowing the age or type of pipe, for example, can help define the schedule and scope of a possible replacement project, so parts of town with significantly older pipe can be prioritized.
4. Central location GIS allows you to tie in a virtually unlimited amount of data to your city – record drawings, curb stops, section corner tie offs, maintenance records, and on it goes. It’s all in one place, and all tied to a map.As an information management system, GIS is exceptionally good at tracking changes in your information and applying it in real time to your displays.
5. Clean and clear display of informationPeople are visual creatures. Intuitive, clear displays are enormously effective for decision making processes. GIS allows you to show all the layers of data you need at once, in a clean format.
Disadvantages of GIS technology.
Geographic Information System is very expensive software , It requires enormous amount of date inputs to be practical for some tasks , It makes it prone for error , It has relative loss of resolution and it has violation of privacy .
Geographic Information System signal needs to be found in remote areas , It is too heavily relied on , The geographic error is increased as you get into a larger scale as the earth is round , Funding for GIS is needed because it is more costly , there will be a loss of knowledge of geography .
GIS layers cause some costly mistakes when the property agents are to interpret the GIS map or the design of the engineer around the utility lines of the GIS , The data availability is a major issue , If the data is not available , then the GIS system is useless .
Disadvantages of using GIS are that its technical nature may portray results as being more reliable than they actually are and the errors and the assumptions can be hidden , leading to a lack of questioning into the results .
Another issue of analyzing the results from a GIS is that the results will only be as accurate as the data that they come from , So , the data may not be able to serve different contexts , particularly if the data is not applicable .
GIS technology is not like the other programs , It does not come off the shelf , So , they must be assembled and constructed to the user design , This could be a long , complex and costly process , So , Some GIS systems can fail in their implementation as their creation was rushed or inadequately planned .
GIS systems are so complex , the technology behind GIS technology expands rapidly, causing GIS systems to have a high rate of obsolescence , As GIS is relatively new , integrating GIS data with traditional maps is difficult .
It’s very hard to make GIS programs which are both fast and user friendly , GIS systems typically require complex command language , Data fields and their accessibility are not very understood and data can become incomplete , obsolete or erroneous , rendering the GIS misleading .
Kyle Volk, “Top 5 Benefits of Geographic Information Systems (GIS)”، www.mooreengineeringinc.com
“GIS (geographic information system)”, www.nationalgeographic.org
HEBA SOFFAR, “GIS Data ( Geographic Information Systems ) uses , advantages and disadvantages”، www.online-sciences.com