Chapter 4: I found chapter 4 interesting because it discusses density mapping and its various applications. This type of mapping is very common because of how useful it is to find patterns in data, and is versatile for this purpose. Density maps can be made from all sorts of data, and can even be made from both features and feature data. In terms of visualization, they can be displayed as dot maps where a dot represents a single instance (or a set number of instances) of the phenomenon being recorded, or as shaded areas where each area has a different shade indicative of the frequency of the phenomenon being recorded in that area. Shaded areas can also be more abstract shapes not defined by manmade borders, such as in a map showing something like rainfall which is not confined by human borders. Dot maps must be considered more carefully than shaded area maps because it is important to choose a value for each dot that allows for the distribution of the data to be clear. For example, you would not want to choose a value so low that the dots appear as one singular mass, but you would not want to choose a value so large that it is unclear which area is being represented. Additionally, depending on the size of the dots, the thickness and detail of borders must be taken into consideration. Because the dots can be obscured by border lines, they should not be too thick and you may want to consider if the borders are useful to the viewer and not include them if they would not be useful in understanding the data. In conclusion, density maps are not very complicated but have various applications for all sorts of data, making them useful in a variety of situations.
Chapter 5: Mapping what’s inside seems to have applications in determining whether action needs to be taken based off of the data that has been collected, and can be used to find patterns in data. Similar to other types of mapping, the data can either be discrete or continuous, which is an important factor to consider when making a map of this type. There are three ways of mapping what’s inside – drawing areas and features, selecting the features inside an area, and overlaying the areas and features. Drawing areas and features involves creating a map showing the boundary of an area and the features that are inside the area. It is a simple method useful for determining if features are inside or outside an area. If the areas being used are discrete, the data can simply be overlaid on top of the area to show the information. For continuous data, a map of the data is first made and a map of the defined area is overlaid onto it. Selecting the features inside an area uses GIS to summarize the features inside of an area. The results that have been collected from a map can be made more concise and understandable by the GIS, using tools like statistical summaries to display the information from the map in a way that is quickly discernable. Overlaying the areas and features uses GIS to combine layers on a map, displaying the overlap between the areas and the features (or lack thereof). This method is useful when dealing with discrete features, however it can also be used when dealing with continuous values. In conclusion, this type of mapping is somewhat complex but can be useful in more specific situations. Each type of mapping what’s inside has its own situations where it is more viable than other forms of mapping.
Chapter 6: Finding what’s nearby is about making maps in order to determine if something is in an area around a selected point, or how much of something is near the point. An important aspect of this type of mapping is whether or not travel is involved. If it is, factors like travel cost and distance may need to be taken into account in the case of something like a tourism guide. Something I found interesting about this chapter is that in some cases it is necessary to take into consideration the curvature of the earth. I had never considered that this would be something map makers had to work around, but it makes sense. As with all maps, finding what’s nearby requires you to know what sort of information needs to be gathered from the map. This will influence how the map is made, for example the mapping of taxi routes in a city would require a different type of map than intercontinental airplane maps which would need to consider the aforementioned curvature of the earth and would result in a different type of map. There are three ways to find what’s nearby. Straight-line distance creates an area around a source point of interest using the distance being measured as the radius of a circle. Distance/cost over a network is slightly more complicated, requiring a source location and a distance or travel cost to be specified. Then, the GIS determines which areas are within the distance or cost. Cost over a surface also requires a source location and a travel cost, and shows the cost proportionate to the distance away from the source location. This type is useful when considering how the distance being traveled will affect the target that is travelling. Finding what’s nearby is similar to mapping what’s inside, but has a greater focus on distance and travel cost.