• GIS (geographic information system)
    GIS allows multiple layers of information to be displayed on a single map.

    Illustration courtesy U.S. Government Accountability Office

    Google GIS
    The interactive maps you view on a phone or the Internet use GIS technology. Using Google Maps, people can add traffic information to road maps or view satellite images of their town or neighborhood.

    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.

    A geographic information system (GIS) is a computer system for capturing, storing, checking, and displaying data related to positions on Earth’s surface. GIS can show many different kinds of data on one map. This enables people to more easily see, analyze, and understand patterns and relationships.

    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, the same map could include sites that produce pollution, such as gas stations, and sites that are sensitive to pollution, such as wetlands. Such a map would help people determine which wetlands are most at risk.

    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 land, 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.

    Data and GIS

    Data in many different forms can be entered into GIS. Data that are already in map form can be included in GIS. This includes such information as the location of rivers and roads, hills and valleys. Digital, or computerized, data can also be entered into GIS. An example of this kind of information is data collected by satellites that show land use—the location of farms, towns, or forests. GIS can also include data in table form, such as population information. 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.

    Putting information into GIS is called data capture. Data that are already in digital form, such as images taken by satellites and most tables, can simply be uploaded into GIS. Maps must be scanned, or converted into digital information.

    GIS must make the information from all the various maps and sources align, so they fit together. One reason this is necessary is because maps have different scales. A scale is the relationship between the distance on a map and the actual distance on Earth. GIS combines the information from different sources in such a way that it all has the same scale.


    Often, GIS must also manipulate the 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. No projection can copy the reality of Earth’s curved surface perfectly. 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 other parts. 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.

    GIS Maps

    Once all of 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. For instance, using GIS technology, many kinds of information can be shown about a single city. Maps can be produced that relate such information as average income, book sales, and voting patterns. Any GIS data layer can be added or subtracted to the same map.

    GIS maps can be used to show information about number and density. For example, GIS can be used to show how many doctors there are in different areas compared with the population. They can also show what is near what, such as which homes and businesses are in areas prone to flooding.

    With GIS technology, researchers can also look at change over time. They can use satellite data to study topics such as how much of the polar regions is covered in ice. A police department can study changes in crime data to help determine where to assign officers.

    GIS often contains a large variety of data that do not appear in an onscreen or printed map. GIS technology sometimes allows users to access this information. A person can point to a spot on a computerized 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 faults.

    GIS technology makes updating maps much easier. 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.

    People working in many different fields use GIS technology. Many businesses use GIS to help them determine where to locate a new store. Biologists use GIS to track animal migration patterns. City 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, where to locate shelters, and what routes people should take to reach safety. Scientists use GIS to compare population growth to resources such as drinking water, or to try to determine a region’s future needs for public services like parking, roads, and electricity. There is no limit to the kind of information that can be analyzed using GIS technology.

  • Term Part of Speech Definition Encyclopedic Entry
    accomplish Verb

    to succeed or complete a goal.

    align Verb

    to put in a straight line.

    assign Noun

    to give or distribute.

    biologist Noun

    scientist who studies living organisms.

    crime Noun

    unlawful activity.

    data Plural Noun

    (singular: datum) information collected during a scientific study.

    data capture Noun

    process of putting information into a geographic information system (GIS).

    density Noun

    number of things of one kind in a given area.

    Encyclopedic Entry: density
    digital Adjective

    having to do with numbers (or digits), often in a format used by computers.

    distortion Noun

    representation that is twisted, mistaken, or false.

    enable Verb

    to empower or allow.

    expensive Adjective

    very costly.

    facility Noun

    a building or room that serves a specific function.

    factory Noun

    one or more buildings used for the manufacture of a product.

    farm Noun

    land cultivated for crops, livestock, or both.

    fault Noun

    a crack in the Earth's crust where there has been movement.

    flood Noun

    overflow of a body of water onto land.

    Encyclopedic Entry: flood
    forest Noun

    ecosystem filled with trees and underbrush.

    geographic information system (GIS) Noun

    any system for capturing, storing, checking, and displaying data related to positions on the Earth's surface.

    Encyclopedic Entry: GIS (geographic information system)
    geologist Noun

    person who studies the physical formations of the Earth.

    hill Noun

    land that rises above its surroundings and has a rounded summit, usually less than 300 meters (1,000 feet).

    Encyclopedic Entry: hill
    hurricane Noun

    tropical storm with wind speeds of at least 119 kilometers (74 miles) per hour. Hurricanes are the same thing as typhoons, but usually located in the Atlantic Ocean region.

    income Noun

    wages, salary, or amount of money earned.

    land use Noun

    range of purposes people put to the earth.

    latitude Noun

    distance north or south of the Equator, measured in degrees.

    Encyclopedic Entry: latitude
    location Noun

    position of a particular point on the surface of the Earth.

    Encyclopedic Entry: location
    longitude Noun

    distance east or west of the prime meridian, measured in degrees.

    Encyclopedic Entry: longitude
    manipulate Verb

    to manage a complex device or situation with great skill.

    map Noun

    symbolic representation of selected characteristics of a place, usually drawn on a flat surface.

    Encyclopedic Entry: map
    map projection Noun

    method by which shapes on a globe are transferred to a flat surface.

    migration Noun

    movement of a group of people or animals from one place to another.

    natural disaster Noun

    an event occurring naturally that has large-scale effects on the environment and people, such as a volcano, earthquake, or hurricane.

    polar Adjective

    having to do with the North and/or South Pole.

    pollution Noun

    introduction of harmful materials into the environment.

    Encyclopedic Entry: pollution
    power line Noun

    cable or cord used to transfer electricity from a power plant to a population center. Also called a transmission line.

    projection Noun

    flat representation of a sphere.

    prone Adjective

    vulnerable or tending to act in a certain way.

    river Noun

    large stream of flowing fresh water.

    Encyclopedic Entry: river
    road Noun

    path, usually paved, for vehicles to travel.

    satellite Noun

    object that orbits around something else. Satellites can be natural, like moons, or made by people.

    scale Noun

    relationship between distances shown on a map and actual distances.

    scan Verb

    to transfer data, usually visual, on to a computer.

    soil Noun

    top layer of the Earth's surface where plants can grow.

    storm drain Noun

    system to empty streets of excess rainwater. Storm drains flow into local creeks, rivers, or seas.

    technology Noun

    the science of using tools and complex machines to make human life easier or more profitable.

    three-dimensional Adjective

    having the appearance of width, height, and depth.

    town Noun

    human settlement larger than a village and smaller than a city.

    upload Verb

    to transfer electronic information from a smaller computer to a larger computer.

    valley Noun

    depression in the Earth between hills.

    vegetation Noun

    all the plant life of a specific place.

    voting pattern Noun

    general way a specific population votes in political elections.

    wetland Noun

    area of land covered by shallow water or saturated by water.

    Encyclopedic Entry: wetland
    ZIP code Noun

    (zone improvement plan) series of numbers used to help locate an address for mail delivery.

Tell us what you think