Chapter 1: Introducing GIS Analysis
Chapter 1 discusses what GIS analysis is along with the types of geographic features and how they are used. “GIS analysis is a process for looking at geographic patterns in your data and at relationships between features” (Mitchell 22). GIS analysis is used to figure out why things are where they are and allows for data to be processed in a way that allows you to visually see how it correlates. There are three types of geographic features, those being discrete, continuous phenomena, and summarized by area. These geographic features have an effect on the analysis process. Discrete features allow for the actual location to be highlighted. Continuous phenomena is continuous data that are values such as precipitation or temperature that can be measured at any part of the map. Features summarized by area is data that is summarized in a way that counts the total number of specifics such as the total population for example. There are two ways of representing geographic features. Those two ways are using different models called vector and raster. The vector model appears to be more organized with each geographic feature being in a row that is in a table. The raster model on the other hand the features are represented in a flush and continuous way. Each geographic feature has a specific attribute that gives information as to what the feature is. The different types of attribute values according to the book are categories, ranks, counts, amounts and ratios. Categories allow data to be organized in groups which helps to condense the information. Ranks put features in order from high to low and are specifically used when it’s hard to get direct measures. Counts and amounts both show a total number and allows you to see what actual value of a feature is. Ratios show the relationship between two quantities by dividing one by another. An important part of GIS analysis is data tables.
Chapter 2: Mapping Where Things Are
Chapter 2 focuses on how maps are made, used and analyzed. Maps allow for people to be able to see where or what something is. By looking at these individual features it reveals patterns that can then further be analyzed. By using these patterns it can answer questions related to individual features. GIS can be used to map the location of different types of features to see whether certain types of these individual features occur in the same place. The most important thing about maps is that they must use certain keys and categories to allow for the person viewing to be able to easily process the information that is being presented. Using specific locations is also important when mapping in case someone viewing it is unfamiliar with the location. This chapter further explains how to prepare data for creating a map and lists the most important steps being to assign geographic coordinates, and category values. The geographic coordinates and category values allow for the information to be more identifiable to the GIS system. For creating maps you have to use this information and tell the GIS which features you want to be shown and what symbols to attribute to them that will be drawn on the map. For mapping a single type you use the same symbol; this is often seen on basic maps that just focus on a specific feature and what patterns can be revealed. The GIS uses the geographic coordinates to draw the features at the coordinate that is listed. To map areas the GIS uses these coordinates to create an outline which is then filled with a specific color or pattern. Another way of mapping is using a subset of features which allows for all types of a specific category values to be shown which can reveal patterns because not all features are shown. While this is helpful for mapping features in a very specific location sometimes this isn’t helpful as more context is needed. The book uses an interesting example of types of zoning and how it might be beneficial to see all the different zones in a lighter color to be able to see the areas around in order to highlight how much area of the map this zone takes up. To map larger areas you would have to take into consideration the scale of the map and the amount of categories that would be used and how you can group them in order to maintain the easy readability of the map.
Chapter 3: Mapping the Most and Least
Chapter 3 focused on explaining why you have to map the most and least. This chapter also gives further information about mapping. The reason for mapping the most and least is to be able to reveal a relationship between places. Mapping the amount can be crucial as it gives a bigger picture besides just showing where something is which is what mapping the locations of a feature is. Going back to the idea presented in Chapter 1 related to geographic features you can map quantities that are associated to discrete features, continuous phenomena and the data summarized by area. By taking these geographic features into account it helps for deciding how to present a map. I feel as though this chapter is very statistics based and focuses on how to properly document and map a specific quantity of a feature. The chapter then further talks about how it is important to understand quantities and how when mapping the most and least you should assign specific symbols that correlate with the features that are based on the specific attributes of these quantities. Relating back to Chapter 1, the specific attribute values can also be used here to map the most and least. Count or an amount can be used to see the value of a feature. Ratios can be used to help identify and reveal relationships between two quantities. Ranks are helpful towards putting features in a specific order which is from high to low. Taking these quantities into consideration allows for the next step which is to decide how you want this data to be displayed on the map. I think to be able to determine which attribute value would be useful you would have to take into consideration the data you have. Once you figure out how to classify and organize the data then a map can be created as it places the information that is given and in turn reveals patterns related to what was inputted.