Luna – Week 2

Chapter 1 of the book really focuses on the basics of GIS. It firstly discusses the chapters of the book and the way that they are ordered so that they teach you to do the basic process that is followed in GIS. Next, this chapter works to make the reader understand geographic features. Firstly, the types of features are covered, including discrete features (features with real locations that can be specified), continuous phenomena (occurrences that are experienced and measured everywhere using locations with boundaries or random sample points), and features summarized by area (the measurement of the features within certain boundaries that apply to the whole area rather than a specific place). Then, the chapter talks about methods of modeling features. The first of these methods is the vector model, where each feature has its own table row and the shapes of these features are shown by their coordinate location on the graph. In the raster model, which is the second method, features are shown using cells in space. This part of the chapter also talks about map projections (shows locations of a spherical globe on a flat map) and coordinate systems (specify units that are for finding the features in a flat space). The next section discusses geographic attributes and the types of them, which are the continuous ones, including categories (groups) and ranks (orders), and the noncontinuous ones, including counts (number of features on a map), amounts (measurable feature quantities), and ratios (relationships between quantities). Finally, the last section covers the use of data tables, talking about the operations used including selecting, calculating, and summarizing. This chapter, as a whole, did a very good job of showing what GIS is all about and why it is needed using the types of features that it is used for to show its need.

Chapter 2 of the book is more about mapping and what goes into that process. The first part of the chapter says that it is important to map things because maps can either show what places meet the requirements, where the most action is needed, or why things are happening. The second part talks about how to decide what to map, firstly saying that the user initially needs to ask what information is actually needed when the analysis is done and how the map will be used. The third part covers how to prepare the data being used, which requires assigning geographic coordinates and category values. The next section of the chapter talks about actually making the map that all of this will be on. This part talks about mapping features of the same type using the same kind of symbol, GIS’s purpose of storing the location as points or shapes, and mapping using feature subsets, which is said to be more common than using individual locations. Next, the books discussed mapping categories, saying that GIS works to store category values for each of the features in the data, making it able to display certain features based on their type. Symbols or colors can be used to differentiate these groupings but the book instructs the user to be careful because too many colors or symbols can make things confusing. This section also suggests that the user use reference features, or landmarks to make it more meaningful to people. Finally, the last section of this chapter discusses interpreting patterns that can be seen in maps. This chapter is a very digestible introduction to actually being able to do things in GIS. While the first chapter talked a lot about the history and use, this one left me feeling better prepared for using the program. 

Chapter 3 is about mapping the most and least, which is said to be useful because it can assist in finding data points that fit in the needed criteria. In order to do this, the values need to have quantities assigned to them, which can be assigned to discrete features, continuous phenomena, or information summarized by area. The next section of this chapter covers the quantities and actually understanding them by more deeply explaining counts, amounts, ratios, and ranks. After this, the book talks about grouping the quantities together into classes, which is said to be particularly useful when it comes to some kind of public presentation because it allows easy comparisons. The text points out that while charting individual values is more accurate as a whole while also allowing raw data patterns to be seen, it is much more effort. Classes, on the other hand require less effort and can be either made manually (when using specific criteria or specific comparisons) or by a standard classification scheme (when grouping to search for patterns). The classification schemes, that are chosen by determining how data is distributed, include natural breaks (finds inherent patterns in data to separate based on those), quantile (each class has the same number of features), equal interval (each class has the same data range), and standard deviation (classes are defined by their distance from the average). This part also talks about outliers and deciding how many classes to use. Lastly, this chapter teaches the reader how to actually make a map using graduated symbols or colors, charts, contours, and 3D views, while also explaining how to effectively use each of those components. This chapter really helped me understand the different ways to interpret data when it comes to GIS, which is different from the past two chapters and will help me when making maps.

Chapter 4 covers the topic of mapping density, and therefore concentrations, of features, which is helpful in recognizing patterns. This chapter talks about how to decide what to include in the map, which requires knowing what kind of data is being used and what kind of values need to be included, meaning either locations or features of the locations. There are two ways to map density. The first uses features summarized by area and should be used when there is previously summarized data or defined borders while the second includes making a density surface using the GIS and should be used when looking for the concentration in features. Next, this chapter talks about how to map density in defined areas, which can be done by finding a density value for those areas, making a map with dot density, or asking the GIS to summarize the features. Lastly, this chapter explains how to create a density surface. The GIS defines an area based on the radius that the user specifically determines, counts the number of those features in that circle, and divides that counted value by the area of the circle. The way that the GIS determines this relies on multiple factors, including cell size (the coarseness of the patterns), search radius, calculation method (either simple or weighted) and units. The density surface is then displayed with contour lines, which connect equal density points on that generated surface, or graduated colors, which can either be used by creating custom ranges or commonly used classification schemes. Finally, the user must view and interpret the result, which mainly involves finding patterns that depend on what kind of density surface was made. This chapter was a bit more confusing for me, but still helped me to further my understanding in the topic of GIS, especially once I get to do it for myself.