GIS Education Center

How does a GIS make Smart Maps?

Glad you asked. Because our environment is dynamic, a GIS also has to be dynamic, flexible, and intelligent to reflect this. With a map display, users can update and maintain their environment or even design new environments.

With a GIS you can...
• Dynamically update information: changes in your GIS are automatically reflected on your map
• Change symbols and labels quickly: modify the look, color, or size of features and labels
• Add layers of data: add many layers of information (e.g. roads, neighborhoods, schools etc.)
• Query data: use expressions to derive results, such as "what neighborhood has the highest level of crime?"
• Perform simple and complex analysis: analyze and produce queries and models that yield answers to questions, such as "what is the solar capacity for rooftops in San  Francisco?"
• Disseminate spatial data easily: share your maps and data over the web
• Publish electronic or hard copy maps quickly: produce quality and professional looking maps

A GIS is a rich interface that works with spatial data, models the real-world, and performs spatial analysis. Modeling the real-world provides a platform to assess our current, past, and future environment; spatial analyst tools enable GIS users to test scenarios to help augment research and guide policy. GIS is the only technology to perform spatial (location-based) analysis and is applied in many fields. For example:

Ever wonder why retailers ask you for your ZIP code?
It's because they use this information in a GIS to analyze where and who their customers are (profiling) as well as to make sure you get their Spring catalog.

What about the impact of a new shopping center or industrial plant in your area?
GIS is used to assess air pollution from traffic or plant burn-off, to model habitat destruction and predict effects on human health.

How about the next earthquake or hurricane?
GIS is a critical component in understanding and preparing for natural and man-made disasters. It can answer questions involving the location of emergency shelters or the likely populations that might be affected by the accidental release of a chemical plume.

You can think of GIS as designing "smart maps" that display correct distances, locations, and enable spatial analysis. In a nutshell, a GIS links information in a database (like a spreadsheet) with graphics on a map.  Once you recognize the power that this linkage yields, you can see some of the many advantages of a GIS.

Lastly...
If you didn't know already, a GIS is database-driven; however, users interact with the database in a visual interface - the map. The database framework provides many benefits for users:

• Serving as a central repository for data, reducing data redundancy
• Integrate with existing databases - use a GIS to view and analyze existing data
• Rules and relationships ensure strong data integrity to reduce errors
• Store large datasets which can be searched, updated, and maintained easily

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Second Powerful Benefit of GIS

As mentioned above, the first powerful benefit of a GIS is to represent your spatial data correctly on the earth. The second powerful benefit has to do with the information about a location. All locations, or features, can or will contain additional characteristic information like the type of feature or other descriptive qualities (or quantities); these are called "attributes" in a GIS. Examples include:

Feature Type: Point Tree Common Name: Monterey Pine Scientific Name: Pinus Radiata Diameter: 16" Condition: Good Region: Coastal California

Feature Type: Point Store #: 101 Store Name: M's Doughnutz Store Type: Food Employees: 150 Daily Sales: $55, 950

Feature Type: Line Type: Utility Subtype: Water Diameter: 8" Material: Concrete Condition: Poor

(Number of families by neighborhood and attributes for West of Twin Peaks neighborhood. Source: SFGIS - Planning Neighborhoods)

In a GIS the location and attribute information are linked. This linking is the second powerful benefit of a GIS as it allows data to be managed, analyzed, and viewed in a graphic or tabular/spreadsheet format.

(Population density in San Francisco, represented with shades of orange, and the ten Census tracts with the highest percentage of renters, highlighted in blue on the map and in the linked database. Source: SFGIS and US Census Bureau)

The linking of graphics and records is the key aspect to a GIS as it establishes a bi-directional relationship between records and graphics. This means you can select or query records in the table to highlight the corresponding features in the map. Or select features in the map to highlight their records and get their attribute information. The select functions in a GIS are critical when it comes to performing spatial analysis and other GIS functions.

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Third Powerful Benefit of GIS

This brings us to our third powerful benefit of GIS - the ability to query using attributes and/or location. Because GIS is database driven it provides the typical database query functionality (greater than, like, range, etc.) or equations you'd find in Excel (sum, average, mean, etc.). However, GIS provides a unique query function that separates it from traditional database applications - the ability to query based on location.

An example demonstrating the third powerful benefit: In this scenario, you're at the Northern California Regional Response Center and there's a chemical release from a plant. You'll need to know which fire departments can respond, what hospitals can handle a large number of patients, and identify the high areas of elderly and young.

First you'd select based on attributes:

• Select FROM "Fire Department" That are RESPOND TYPE "Chemical";
• Select FROM "Hospitals" that are TYPE "Emergency Room" AND have greater than "1000 Beds";
• Select FROM "Census tracts" that are TYPE "65 and Older" OR "5 and Under" that have greater than "1000";

Now, highlighted on your map are the locations of fire departments that can respond, hospitals that can handle a large capacity of patients, and those census tracts where there's a large number of elderly and young in the region. This is a great start but your region is Northern California and the incident is in Monterey, Ca (sorry citizens of Monterey) which means all the services in upper Northern California are too far away to assist. What you need is a query to select those services within 10 miles of the incident - from the already selected services. This is something only GIS can do.

Select based on location:

Select FROM the SELECTED "Fire Departments", "Hospitals", and "Census tracts" that are within a distance of "10 miles" from the incident.

Result:

Now, your map has identified the appropriate services. You can then begin notifying hospitals and local authorities about the problem and set in motion the Standard Operating Procedures for such an incident.

This example demonstrates the powerful and unique capabilities of GIS. And it also demonstrates how GIS help us make better decisions.

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Fourth Powerful Benefit of GIS

GIS allow students, researchers, and professionals to incorporate a spatial quality to their projects.  Consider this example: a spreadsheet (like Excel files) or a relational databases (such as a Microsoft Access file) might list a number of customer addresses.  While this information is valuable, by itself it is hard to discern patterns, locational relationships and other geographic qualities (such as "how many of these addresses are in my market study area?").  However, in a GIS, the customer locations can be linked to points on a map.  After doing so, the adage "a picture is worth a thousand words" really is true!  Now that the customers are shown on a map, locational relationships are revealed and more in-depth analysis can take place. In short, then, a GIS links information about where things are with information about what things are like.

(Coffee shops in San Francisco and neighborhoods. Source: Online research by Rick Kos and Mono Simeone; SFGIS - Planning Neighborhoods)

Another example: children and the elderly are more susceptible to harmful air pollutants. As a GIS user, you would most likely want to produce a map composed of individual map layers related to this topic.  Such map layers might include locations of reported respiratory problems, neighborhoods, parks, schools, roads, and Census tracts.

(Source: SFGIS - Planning Neighborhoods, Public Schools, Major Roads, Parks)

Additional information and analysis of air pollutant, traffic data, and weather patterns could provide further insight into the spatial patterns and relationships. These examples demonstrates the fourth powerful benefit of GIS - the ability understand and/or model our environment by analyzing spatial phenomenon.

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Fifth Powerful Benefit of GIS

The fifth powerful benefit of a GIS is the ability to publish maps - online maps or high-quality cartographic maps. In the past, design applications like Illustrator or Freehand were used to publish maps. Recently, GIS has developed robust cartographic capabilities and tools to reduce the need for other applications. To learn more about cartographic design in GIS sign up for our Information Design with Maps workshop.

If you wish to learn more about GIS, please sign up for our free, introductory GIS Theory & Practice workshop.  Or, if you are interested in taking an introductory GIS workshop,  please consider our GIS Quick Start.