Steed – Week 3

Chapter 5

This chapter explains how and why GIS users analyze data inside an area, and specifies the advantages and disadvantages to using various mapping methods. First, Mitchell examines why people map different areas. He states that people map “to monitor what’s occurring inside it, or to compare several areas based on what’s inside each.” For example, a police officer would be interested in analyzing how many people on parole are still in their specified areas; if a person is outside of their specified region, then a warrant may be issued. Next, the author emphasizes the importance of determining what information is necessary when attempting to map out a problem. The following questions are ones he deems critical: are you mapping a single or multiple areas?; are the features continuous or discrete?; do you need a list, count, or summary?; and do you need to see the features completely or partially inside the area? Then, Mitchell analyzes three different mapping methods: (1) drawing areas and features, (2) selecting features inside an area, and (3) overlaying areas and features. He provides short synopses for what each method is good for, what you need to utilize the method, and how GIS visualize these methods. Finally, the author goes into further detail about each method and provides tips and trips to better assemble and analyze maps.

Overall, I found this to chapter to be helpful in providing tips into better defining map data so as not to confuse observers, but also in creating better analyses for the user. Although I did find this reading to be very redundant with the majority of points being made multiple times throughout. I will be utilizing this chapter in particular to troubleshoot if I run into any issues analyzing data.

Chapter 6

This chapter explains the significance of mapping the distance around an area and specifies three manners in which the process can be done. First, the author states why people map near specified areas and examines various questions that he finds to be important in configuring how to better define problems. Then, he states the three types of mapping processes utilized to map nearby: (1) straight-line distance, (2) distance or cost over a network, and (3) cost over a surface. Before defining each individually, Mitchell compares each type with one another and clarifies which mapping method is best for different situations. Next, he begins to describe the straight-line distance method, which he says is when “you specify the source feature and the distance, and the GIS finds the area or the surrounding features within the distance.” For example, you might have a toxic waste spill at a nuclear plant and need to know how many houses or businesses are within a 10-mile radius of the nuclear plant to properly evacuate the region. In addition, Mitchell examines measuring distance or cost over a network. This is when “you specify the source locations and a distance or travel cost along with each linear feature, and the GIS finds which segments of the network are within the distance or cost.” Furthermore, Mitchell defines the final mapping method, calculating cost over a geographic surface. This is when “you specify the location of the source features and a travel cost, and the GIS creates a new layer showing the travel cost from each source feature.” For example, you may have a river that has been commonly used as a dumping ground for animal waste by a local farmer, and the river sits on an uneven surface over a large stretch of land. You may need to use GIS to calculate the cost distance of river runoff to help better prepare for cleanup.

Chapter 7

This chapter primarily explains the importance of mapping change and provides the necessary logistical tools to create an easily digestible map utilizing different data. First, the author examines the various types of change that can be defined through geographics. He says, you can either map the change in location, which “helps you see how features behave so you can predict where they’ll move,” or the change in character or magnitude, which “shows you how conditions in a given place have changed.” For example, one mountain may shift a few inches a year due to plate tectonics, so scientists may be interested in plotting this information in GIS. Then, Mitchell defines the various methods of mapping change including time series, tracking maps, and measuring change. He states that time series are “good for showing changes in boundaries, values for discrete areas, or surfaces.” In other words, good for locations that are constant, or never move. Tracking maps are “good for showing movement in discrete locations, linear features, or area boundaries, which is like time series, but can include features for several dates and times. Finally, he explains measuring change shows “the amount, percentage, or rate of change in a place.” For example, you may measure change within a small village following a mudslide or a tornado to understand the full impacts of the natural disaster event.

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