Notes from Chapter 1 of The ESRI Guide to GIS Analysis by Andy Mitchell

What is GIS Analysis?

“A process for looking at geographic patterns in your data and at relationships between features.”

There are 5 steps to performing GIS Analysis:

  1. Frame the question
    • Need to figure out what information you need by posing a question you intend to find out, such as how much pollution is being released into the air by the top polluters in the area or how much public ‘green’ space is in the county and where it is located.
  2. Understand your data
    • Need to determine what kind of data you are going to use and how you will obtain it. Sometimes a special method is required to obtain some data.
  3. Choose a method
    • Deciding on what kind of method you will use to obtaining the information you need depends on the question you are trying to answer and on how specific you expect the answer to be.
  4. Process the data
    • After collecting the data you then perform the necessary steps in the GIS in order to process the data.
  5. Look at the results
    • The results of the GIS analysis can be displayed in multiple formats such as a map, values in a table, or a chart.

Types of Geographic Features Represented on maps

Discrete Features: at discrete locations, the location of an object can be pinpointed

Continuous Phenomena: this type of feature is seen in precipitation or temperature maps. This feature often starts as sample points such as irregularly placed weather stations

Features Summarized by Area: represents the counts or density of individual features within area boundaries. (Good Example off this type of feature in my population change maps)

Understanding Geographic Attributes

  • Categories – groups of similar things that are put together to help the reader understand the data better. (Ex. – roads are categorized by whether they are a freeway, highway, local road, or others.
  • Ranks – puts features in order from high to low or vise versa
  • Counts – this shows total numbers for each individual data points such as the amount of employees each company in a city employs.
  • Ratios – relationships between two quantities such as the average number of people per household.