Schtucka week 2

Going into the first chapter of Mitchell, I knew very little about GIS. However, by reading this chapter of the book, I became a lot more familiar with the concept. Chapter 1 was able to help me get a better understanding of what GIS is as a whole and also the breakdown of the software. One thing that I learned is that GIS has many different tasks and things that you are able to use it for. Before reading, I knew that there was a wide use of GIS. However, on page 13 of Mitchell, the book states a list of what GIS is most commonly used for. The list goes, in no particular order, “mapping where things are, mapping the most and least, mapping density, finding what’s inside, finding what’s nearby, mapping change.” This list is helpful to me because it gives me a more narrow idea of what GIS is used for instead of the “wide use” mindset that I previously had. Furthermore, the most interesting thing I learned is that in GIS there are different operations that you are able to perform on data tables. These caught my attention because they are different, useful tools that I did not know that GIS was able to do. The first operation is selecting; you are able to assign a value to a feature. The second operation is calculation; you can calculate attributes’ values in order to give new values to the features. The third operation is summarizing; you are able to get different statistics for specific attributes. I think that it is really interesting when you are able to find shortcuts or codes in different software in order to use it more efficiently. I believe that later on in my GIS learning and use, these operations will become very useful. 

 

The second chapter of Mitchell is all about mapping. Mapping is important because when you map things, you are able to look and see where you could potentially need to take action or what areas are able to meet your criteria. One fun thing I learned about mapping from Chapter 2 is that it is typically helpful to add different categories to your map. Categories split up features into different subtypes and aid the readability and fluidity of a map. Without categories, it might be hard to determine certain uses for your map and it may be difficult to read under certain contexts. Mitchell states that “mapping features by category can provide an understanding of how a place functions.” Mitchell then gives the example of how using a black line for road types only shows where the roads are, but if you categorize them into types of roads, the hierarchy of the roads would be visible along with regional traffic patterns. This shows that categories are extremely helpful when creating a map. In this example, adding categories gave the map a new function and made it easier to read. However, adding categories can be tricky to do properly. Mitchell says that there should never be more than 7 categories because the more categories you use, the more difficult reading your map will be. A few factors play into the 7 category rule: scale of features and map scale relative to features. One thing to keep in mind is that the scale of the features on a map can greatly influence the number of categories used. If the features on a map are small, it will be difficult to distinguish which categories are which if there are too many used. Also, if the map scale is large in scale to the features, the more categories used, the more difficult the categories are to see.

 

I found the third chapter of Mitchell particularly interesting because it was all about creating a map. I liked how this chapter was set up compared to the other chapters. This chapter was formatted by walking the reader through creating a map by telling them what questions to ask themselves in the process. These questions were the headings for each section, and the section would walk the reader through what to consider in order to answer the questions properly. My favorite section of this question system was about classes. Classes allow the person mapping to group together different values into classes, and they are typically utilized when the map will be presented for discussion instead of for individual analysis. I think the concept of classes is cool because they let the mapper create groups of data and then assign the different groups a symbol. Another thing I thought was interesting about classes is that they can be made manually or by the GIS program. Mitchell states that creating classes manually is usually used when the person creating the map is looking “for features that meet specific criteria or comparing features to a specific, meaningful value.” When creating classes using GIS software, the person mapping will use a standard classification scheme. Mitchell states that the person mapping will want to use a standard classification scheme when they “want to group similar values to look for patterns in the data. You can choose from several schemes.” I found standard classification schemes particularly interesting because there are multiple different ones that are available. There are natural breaks, quantile, equal interval, and standard deviation. In my opinion, Mitchell did a really good job breaking down the different types of classification schemes by stating how each one works, what it is good to use it for, and the disadvantages of using it.