Have you ever looked at a map of crime in your community and tried to figure out what areas have high crime rates? Have you explored other types of information, such as school locations, parks, and demographics, to try to determine the best location to buy a new home?
Whenever you look at a map to answer these questions, you inherently start to turn that map into information by analyzing its contents—finding patterns, assessing trends, or making decisions. This process is called spatial analysis, and it’s what your eyes and minds do naturally.
Spatial analysis is the most intriguing and remarkable aspect of GIS. When you do spatial analysis, you combine information from many independent sources and use sophisticated spatial analysis tools to derive new sets of information (i.e., your results).
These tools help you answer complex spatial questions. Statistical analysis can determine if the patterns that you see are significant. You can analyze various layers of data to calculate how suitable a location is for an activity, such as opening a new store. Using image analysis, you can detect change over time.
These tools and many others, which are part of Esri’s ArcGIS, enable you to address critically important questions and decisions that are beyond the scope of simple visual analysis. Spatial analysis lets you do the following:
Understand and Describe Locations and Events
Detect and Quantify Patterns
Find Best Locations and Paths
How Is Spatial Analysis Used?
Spatial analysis lets you pose questions, derive answers from data, and then make informed decisions. The organizations that use spatial analysis in their work include state and local governments, national agencies, businesses of all kinds, utility companies, colleges and universities, and nongovernmental organizations (NGOs).
How do these organizations use spatial analysis? The list below touches on a few well-known uses:
The source data is available at no cost for land-use planning and the creation of information products that help everyone understand the importance of preserving the nation’s remaining natural resources. Read the 6 Step Guide to Green Infrastructure to learn more about green infrastructure planning.
Automatic Data Interpretation
What Can My Map Show Me?
In many cases, you are doing analysis just by making a map. You have a question you want the map to help answer: Where has disease ravaged trees? Which communities are in the path of a wildfire? Where are the areas of high crime? As with any analysis, when you make a map, you’re making decisions about which information to include and how to present that information. Effective visualization is valuable for communicating results and messages clearly and in an engaging way.
Visual and Visibility Analyses
Visualizing Solar Radiation Exposure
At the moment Confederate General Robert E. Lee (at the red eye on the map) committed to engage with Union troops, he could see only the troops in the light areas; everything shaded (the much greater part of the Union’s strength) was invisible to him. Historians using personal accounts, maps of the battle, and a basic elevation layer were able to unlock the mystery of why Lee may have decided to go into battle facing such poor odds.
This article is an excerpt from The ArcGIS Book,Second Edition: 10 Big Ideas about Applying The Science of Where. The twin goals of this book are to show you what is possible with Web GIS and then spur you into action by putting the technology and deep data resources in your hands. The book is available through Amazon.comand other booksellers, and it is also available at TheArcGISBook.com for free.