Geographical Information System

Answering Questions with GIS

GIS is fundamentally used to answer questions and make decisions. To use GIS properly, it is important to know what we want to ask and follow a disciplined process for getting the answer.

1. Frame the question.

Start your GIS analysis by figuring out what information you want,  most often in the form of  :

• Where were most of the supplies last month?

• How much forest is in each watershed?

• Which schools are within 500 feet of a wine / arrack shop?

Be as specific as possible about the question you want to answer. This will help you decide how to approach the analysis, which method to use, and how to present the results.

2. Select your data.

The type of data and features you work with help determine the method you use. Or, if you know you need to use a specific method to answer your question, you may find you need additional data.

Data can come from any number of sources—databases within your organization, contact managers, CAD files, the Internet, commercial data providers, government organizations, and so on.

Data should be of good quality and  accurate.

3. Choose an analysis method.

Decide which analysis method to use based on your original question and how the results of the analysis will be used.

For example, if you are doing a quick study of land use in a district to look for patterns, you might just map the lands and look at the maps. 

4. Process the data.

Once  the analysis method is selected,  you'll need to process your data in a way that makes sense for your goal.

If you are mapping where things are located, you may need to assign geographic coordinates, such as latitude and longitude or address, to your data and assign category values to the data.

If you are mapping quantities, like  number of vegetation types in a state park, you may need to choose a classification scheme and decide on how many classes to represent your data.

If you are trying to find out what is inside, you may need to measure an area or combine different layers of information.

5. Look at the results.

The final step is to look at the results of your analysis and take action accordingly.

Your results can be displayed as a digital map, printed as a paper map, combined with spreadsheet-like tables or charts, or displayed as such.

Though a lot of emphasis in GIS is in making maps, the software is flexible enough to allow you to display your results in the format that best suits your needs.