Chapter 4: Mapping Density
Chapter 4 focuses on mapping density and how it is done and the reason why it is needed. Mapping density allows you to see where the highest concentration of features is. Density is more useful when it comes to looking at patterns than individual features. Mapping density is also useful when trying to map areas. This chapter then talks about how you can use GIS to map the density of points or lines. There are two different ways of mapping density; those being mapping density by defined area and mapping density by density surface. When mapping density by defined area you can use a dot map or calculate each density value for each specific area. By using a dot map to represent the density of individual locations, each dot would represent a specific number of features. The closer the dots are on this map the higher the density is. Then on the map each area is shaded based on these density values which allows for the viewer to see which areas have a higher density. Mapping density by density surface is usually done in the GIS through a raster layer. To create density surface various information related to specific features and location would be needed. This method is more time consuming but is the more accurate method. Each method is useful for its own reason. For example mapping by defined area would be more effective if you already have the data summarized but mapping by density surface is more effective when you want to see a specific points concentration. Creating a dot density map allows for the viewer to have a summarized and easy to understand way of seeing the density of a specific area. Density surfaces are created in GIS as raster layers. There is a specific density value for each cell in each layer. This helps to show which points or lines are the most concentrated.
Chapter 5: Finding What’s Inside
Chapter 5 discusses the importance of mapping and why it is important to see what is located inside an area. By mapping a specific area it allows for the viewer to be able to see specific patterns and to have an idea of what is occurring. A map condenses and summarizes a specific feature or thing in a location. By having this map it allows us to be able to see where in an area there is more and less of something. When deciding what is inside of your map it is important to take into consideration the data that you are using. It is also important to think about whether you are finding what’s inside a specific single area or finding what’s inside several areas. A single area would be easier to monitor as it would give specific summarized information. With multiple areas it would be more useful for making comparisons. Another important thing that this chapter talks about is considering whether features inside are discrete or continuous. Discrete features are unique and identifiable features and something that you can easily list or count. Continuous features on the other hand aren’t as straight forward and instead represent a variety of different things. GIS is helpful when trying to decide what information you may need from the analysis such as asking the question of whether or not you need a list or a count or a summary. GIS can be used to find out if a specific individual feature is inside an area. There are three ways of finding what’s inside; those being drawing areas and features, selecting the features inside the area, and overlaying the areas and features. Drawing areas and features is useful as it allows for you to have a visual representation of which features are inside or outside the area. Selecting the features inside the area is useful for getting a list or an overall summary of the features inside a specific area or group of areas. Overlaying the areas and features is useful for finding which features are in a specific area.
Chapter 6: Finding What’s Nearby
Chapter 6 discusses the importance of finding what is nearby a feature and how to do so. Using GIS you can find what is nearby a feature and you can set a specific distance. By monitoring what is nearby it allows more information to be able to plan. To find out what is nearby you can measure straight-line distance, measure distance or cost over a network, or measure cost over a surface. Kind of similar to the previous chapter but it emphasizes that you need to have an idea of what information you want from the analysis. There are three ways of finding what’s nearby: that is by using straight-line distance, distance or cost over a network, and cost over a surface. With straight-line distance you have to specify the main feature that you want to use as the source and what distance you want the GIS to look into for finding the surrounding features within this specific distance. This is useful for when you need to create a boundary. Another way of finding what is nearby is by distance or cost over a network. Another way of finding what is nearby is through cost over a surface. This method is useful for calculating overland travel costs. The easiest method for finding what is nearby is straight-line distance. Straight-line distance is a simple way of seeing which features are in a given distance of the main source feature you want to find what is nearby. The next thing this chapter talks about is creating a buffer. In order to create a buffer you have to specify the source feature and then the specific buffer distance; this helps for finding what is inside a specific boundary or area. Once this buffer is created then you can use it to select what features you want to fall within it which allows for you to get a summarized list or count of the features. Overall these chapters have focused more on the content of the maps in comparison to previous chapters from last week which focused on the creation of maps.