What is GIS?
A geographic information system (GIS) integrates hardware, software, and data for capturing, managing, analyzing, and displaying all forms of geographically referenced information.
GIS allows us to view, understand, question, interpret, and visualize data in many ways that reveal relationships, patterns, and trends in the form of maps, globes, reports, and charts.
A GIS helps you answer questions and solve problems by looking at your data in a way that is quickly understood and easily shared.
GIS technology can be integrated into any enterprise information system framework.
Map Where Things Are
Mapping where things are lets you find places that have the features you're looking for and to see patterns.
People map quantities to find places that meet their criteria and take action. A children's clothing company might want to find ZIP Codes with many young families with relatively high income. Public health officials might want to map the numbers of physicians per 1,000 people in each census tract to identify which areas are adequately served, and which are not.
A density map lets you measure the number of features using a uniform areal unit so you can clearly see the distribution. This is especially useful when mapping areas, such as census tracts or counties, which vary greatly in size. On maps showing the number of people per census tract, the larger tracts might have more people than smaller ones. But some smaller tracts might have more people per square mile—a higher density.
Find What's Inside
Use GIS to monitor what's happening and to take specific action by mapping what's inside a specific area. For example, a district attorney would monitor drug-related arrests to find out if an arrest is within 1,000 feet of a school--if so, stiffer penalties apply.
Find What's Nearby
GIS can hrelp you find out what's occurring within a set distance of a feature by mapping what's nearby.
Map the change in an area to anticipate future conditions, decide on a course of action, or to evaluate the results of an action or policy. By mapping where and how things move over a period of time, you can gain insight into how they behave. For example, a meteorologist might study the paths of hurricanes to predict where and when they might occur in the future.
The Geographic Approach
Geography is the science of our world. Coupled with GIS, geography is helping us to better understand the earth and apply geographic knowledge to a host of human activities. The outcome is the emergence of The Geographic Approach—a new way of thinking and problem solving that integrates geographic information into how we understand and manage our planet. This approach allows us to create geographic knowledge by measuring the earth, organizing this data, and analyzing and modeling various processes and their relationships. The Geographic Approach also allows us to apply this knowledge to the way we design, plan, and change our world.
Next: Step 1: Ask
Frame the Question
Approaching a problem geographically involves framing the question from a location-based perspective. What is the problem you are trying to solve or analyze, and where is it located? Being as specific as possible about the question you're trying to answer will help you with the later stages of The Geographic Approach, when you're faced with deciding how to structure the analysis, which analytic methods to use, and how to present the results to the target audience.
Next: Step 2: Acquire
After clearly defining the problem, it is necessary to determine the data needed to complete your analysis and ascertain where that data can be found or generated. The type of data and the geographic scope of your project will help direct your methods of collecting data and conducting the analysis. If the method of analysis requires detailed and/or high-level information, it may be necessary to create or calculate the new data. Creating new data may simply mean calculating new values in the data table or obtaining new map layers or attributes but may also require geoprocessing.
Next: Step 3: Examine
Examine the Data
You will not know for certain whether the data you have acquired is appropriate for your study until you thoroughly examine it. This includes visual inspection, as well as investigating how the data is organized (its schema), how well the data corresponds to other datasets and the rules of the physical world (its topology), and the story of where the data came from (its metadata).
Next: Step 4: Analyze
Analyze the Data
The data is processed and analyzed based on the method of examination or analysis you choose, which is dependent on the results you hope to achieve. Do not underestimate the power of "eyeballing" the data. Looking at the results can help you decide whether the information is valid or useful, or whether you should rerun the analysis using different parameters or even a different method. GIS modeling tools make it relatively easy to make these changes and create new output.
Next: Step 5: Act
Share Your Results
The results and presentation of the analysis are important parts of The Geographic Approach. The results can be shared through reports, maps, tables, and charts and delivered in printed form or digitally over a network or on the Web. You need to decide on the best means for presenting your analysis. You can compare the results from different analyses and see which method presents the information most accurately. And you can tailor the results for different audiences. For example, one audience might require a conventional report that summarizes the analyses and conveys recommendations or comparable alternatives. Another audience may need an interactive format that allows them to ask what-if questions or pursue additional analysis.
There are many online glossaries of GIS terms and acronyms. We recommend you compare the definitions from three sources to get a comprehensive idea of what the term means.
- GIS Wiki: wiki.gis.com
- Dictionary of Abbreviations and Acronyms in GIS, Cartography, and Remote Sensing—University of California at Berkeley
- ESRI Online GIS Dictionary
- FGDC Glossary—most terms are from the Spatial Data Transfer Standard (FIPS 173)
- Geographer's Craft Glossary—University of Colorado at Boulder
- GIS Data Depot Helpdesk Glossary
- Glossaire SIG—French-language glossary from ESRI-France
- Glossary of Cartographic Terms—Perry-Castañeda Library, University of Texas at Austin
- ArcNews—A magazine featuring GIS success stories.
- ArcUser—A magazine for ESRI software users.
- ArcWatch—E-magazine for GIS news, views, and insights.
- A Very Spatial Podcast
- Directions Magazine
- Geo: International Magazine
- Geospatial Solutions
- Geospatial Today
- GIS Café
- GIS Development
- GIS Lounge
- Imaging Notes