Open Educational Resource
Open Educational Resource



GIS (Geographic Information System)

GIS (Geographic Information System)

A geographic information system (GIS) is a computer system for capturing, storing, checking, and displaying data related to positions on Earth’s surface.


4 - 12+


Geography, Geographic Information Systems (GIS), Physical Geography

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If you have ever used Google Maps or GPS when traveling, then you've experienced the power of GIS.

A geographic information system (GIS) is a computer system for capturing, storing, checking, and displaying data related to positions on Earth.

It 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, and we can find out how that information relates to each other. It tells us about the landscape and people around us. GIS is an important tool for many different jobs.

Data Capture
Data Formats
GIS data comes in many forms.

One example is cartographic data, or map data. This might include such information as the location of rivers, roads, hills, and valleys. Cartographic data might also include survey data, or mapping information, which can be directly entered into a GIS.

Interpreting photographs is a major part of GIS. Photo interpretation involves analyzing photographs from above and assessing the features that appear.

Digital data can also be entered into GIS. For example, computer data collected by satellites can show how land is used, plus the location of farms, towns, and forests. Satellites can also use GIS to capture images in a tool called remote sensing.

Finally, GIS data can also be collected from tables or spreadsheets. One example of this is population demographics. This is when people are grouped into certain categories. Some examples are age, income, and ethnic background, or even internet browsing history.

GIS technology allows all these different types of information to be overlaid on top of one another on a single map. Location is the key data point that connects seemingly unrelated information.

Spatial Relationships
GIS technology can be used to display spatial relationships and linear networks.

Spatial relationships may display topography, such as farmland and streams. They may also show patterns of how land is used, such as the location of parks and neighborhoods.

Examples of linear networks are roads and rivers. A line on a map might indicate a road or highway. With GIS layers, however, that road may indicate the boundary of a school district, public park, or other land-use area.

GIS must make the information from all the various maps and sources 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 and move data because different maps have different projections. A projection is a way of moving 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. Whenever this happens, there is some distortion. You can't put a curved, three-dimensional shape onto a flat surface without 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. It 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. One of the most common uses of GIS involves comparing natural features with human activity.

For instance, GIS maps can display what 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 voting patterns or the average amount of money made by people there. 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 movement and disappearance of ice cover in the North Pole. A police department might study changes in crime data to help determine where to assign officers.

Photography and 3-D Images
One important use of time-based GIS technology involves creating time-lapse photography. It shows processes changing over large areas and long periods of time. For example, data showing the movement of fluid in ocean 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. For example, a user might click on a school to find how many students are enrolled there or how many students there are per teacher.

Three-dimensional images are often produced with GIS systems. This is useful, for example, to geologists studying fault lines, where earthquakes happen.

It's also easy to update maps because of GIS technology—data can simply be added to the existing program. A new map can then be printed or displayed on screen. This skips the old way of drawing a map, which takes time and money.

GIS Jobs
GIS technology is used for many jobs.

Many retail businesses use GIS to help them determine where to locate a new store. Scientists use GIS to compare population statistics to resources such as drinking water. Biologists use GIS to track animal-migration patterns.

City, state, or federal officials use GIS to help plan their response in the case of a natural disaster such as an earthquake or hurricane. GIS maps can show these officials what neighborhoods are most in danger or where to locate emergency shelters.

Engineers use GIS technology to design and manage the cellphone and Wi-Fi networks we use. Other engineers might use GIS to develop road networks and transportation infrastructure.

There is no limit to the kind of information that can be analyzed using GIS technology.

Fast Fact

Earth Science Information Center
To find out more about how GIS is used in your local community, contact your nearest Earth Science Information Center (ESIC). Staff from the US Geological Survey (USGS) answer questions about aerial photographs, maps, satellite imagery, computer programs, data formats, data standards, and digital cartographic data. To contact your local ESIC, call 1-888-ASK-USGS or visit the website.

Fast Fact

Neogeography is a controversial term that often describes user-generated location data or “citizen geographer” platforms. Neogeography may describe projects as varied as the massive collaborative effort of OpenStreetMap and auto-generated location tags in social media.

Fast Fact

The labor-intensive process of photozincography anticipated GIS in the 19th century. This process used zinc plates to draft different layers of a map, and a large-process camera to combine the layers into a single image.

Media Credits

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Jeannie Evers, Emdash Editing, Emdash Editing
National Geographic Society
Last Updated

February 22, 2024

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