Chapter 4-
This chapter starts by explaining the difference between mapping features and feature values as densities. Mapping a feature would show the density of a business in a particular area, whereas mapping a feature value might show the density of workers at the business. Itâs interesting how different these two maps look, even though the data seems fairly similar. The density maps are a little confusing right now, but I think it will make more sense when weâre creating them in the lab ourselves. The book does mention not to make dots too big when graphing density, otherwise, it is hard to pick out the patterns since they all mesh together. Also, this chapter mentions not to use too many classes when graphing density surfaces, otherwise the colors are hard to distinguish. I think itâs an interesting idea to make a map using light colors for high density because itâs usually the other way around. Although, the book mentions that the readerâs eye is drawn to the light color, and I think this is true. This chapter taught me that density maps are useful because they display patterns rather than features, which is very beneficial for real-world applications. The book mentions that crime analysts, transportation planners, and urban planners can all use density maps for their jobs. This chapter also emphasizes the idea that itâs important to decide what kind of data you have before choosing what kind of map to make and how to map it. The chapter presents many different ways to map densities, such as dots, graduated colors, or contours. There are many useful images that show common mistakes people make when mapping densities and how to fix them in order to create an effective map.Â
Chapter 5-
Chapter 5 is about mapping whatâs happening inside a certain area. When a map is made based on data occurring inside the area, trends can be tracked and policies or courses of action can be made based on the data. The book mentions that firefighters could use this method when there are toxic plumes so they know what areas are being affected. Also, mapping data inside an area can be done with one specific area or multiple areas. When mapping multiple areas, this would be used to compare certain trends or patterns. One thing I find interesting about all these methods is how much you can manipulate the map to display a very specific type of data in a way that is easy to understand. This chapter goes on to explain the three different ways of finding out what is inside an area: drawing areas/features, selecting certain features, or overlaying the area/features. These all have instances when they are most beneficial, so I think that you would just have to decide what kind of map you want to portray. This chapter has another chart comparing all of these methods that has pros and cons, which I think Iâll look back on later! One thing I like about this chapter, and the others before, is how it builds on material from the other chapters. It incorporates terms and ideas that were introduced earlier, like discrete or continuous features, and almost forces you to learn what they mean. I think building the information up like this is a very effective way of teaching this subject. I think maps based on whatâs happening in an area have many diverse applications and it will be interesting to see how these are made in practice.Â
Chapter 6-
Chapter 6 seems similar to 5, but it explains how to map what is nearby rather than inside an area. These maps are useful because you can specify a distance and analyze data within that set amount, or you can even use them to calculate travel costs and mileage. I think itâs interesting how this method can be measured using either a set distance or a set cost. If you have a budget, you can determine how far you can travel based on that budget. You can also take into account the time it takes to travel somewhere based on heavy or light traffic. Like the last chapter, this chapter explains the three different methods of mapping whatâs nearby- straight-line distance, distance/cost over a network, and cost over a surface. These methods all vary in precision and uses, and it also depends on what type of data you have available to input. I think that mapping distance may seem like a fairly simple task or something that is just intuitive when looking at a map, but itâs interesting to see all the work that goes into creating maps like this. Also, the work that gets put in to make these maps means that people can look at them and read them easily. I like how each of the chapters goes into detail about what the GIS does when youâre making a map. Itâs interesting to know what is happening âbehind the scenesâ. Itâs nice how this book talks about things that you can do to make maps and show data, while also explaining the way the computer helps you out. I think it explains these concepts in a way that isnât overwhelming and gives you just enough information to understand the process.