Chapter 4-
Chapter 4 discusses mapping the density of features, why to do it, and how to do it, so you can more accurately compare areas and know if certain areas fit your criteria. The first subsection, âwhy map density,â describes how it shows you where the highest concentration of features is and how it’s good for looking at patterns in features. If you have multiple features on a map, or when you’re mapping areas, mapping density can help to differentiate easier. âDeciding what to mapâ asks you to consider what kind of data you have, if you want to map features or feature values- feature values being the number of employees at a business vs. the location of businesses, for example, since the two can create different patterns. âTwo ways of mapping densityâ describes mapping density by defined area- by mapping it graphically, using a dot map (which doesnât actually show exact locations just the density of features in an area), or by calculating a density value for each area, and by creating a density surface- each cell in the raster layer gets a density value, typically if you have individual locations, sample points, or lines. The next two subsections go into extreme depth on how each method works, how to do it, and what the GIS does.Â
Chapter 5-Â
Chapter 5, âFinding Whatâs Inside,â describes why you should map whatâs inside, defining your analysis, ways of finding whatâs inside, drawing areas and features, selecting features inside an area, and overlaying areas and features. The first subsection, âwhy map whatâs inside,â states that you can look at what’s happening inside an area, or compare whatâs happening in several areas based on whatâs inside. You can know whether to take action by observing one. âDefining your analysisâ describes how depending on your data, you can either draw an area boundary on top of the features, use an area boundary to select the features inside and list or summarize them, or combine the area boundary and features to create summarized data. The subsection goes in depth on what you need in order to make a decision and why. âThree ways of finding whatâs insideâ describes drawing areas and features as a way to find what’s inside- creating a boundary of an area and features to see what’s inside and out, selecting the features inside the area, and overlaying the areas and features- the GIS combines the area and the features into a new layer or compares two layers, and the subsection also compares each method and what features best suited for them. âDrawing areas and featuresâ describes the actual process of finding what’s inside, by making a map to see what features are inside the area either using locations and lines, discrete areas, or continuous features. âSelecting features inside an areaâ is a method where you specify the features and the area, then highlighting selected features on a map and putting them into a data table, or can summarize an attribute associated with the features. âOverlaying areas and featuresâ is a method for discrete features or continuous ones.
Chapter 6-
âFinding Whatâs Nearby,â talks about how this lets you see whatâs in a set distance or travel range of a feature to monitor events in an area or find an area served by a facility or the features affected by an activity. The first subsection, âwhy map whatâs nearby,â talks about how finding whatâs in a set distance identifies an area and the features inside an idea affected by an event or activity. âDefining your analysisâ describes how in order to find whatâs nearby, you can measure straight line distance, measure distance or cost over a network, or measure cost over a surface, and how the information you need from the analysis will help to choose the best method. âThree ways of finding whatâs nearbyâ goes more in depth about the previously mentioned methods, what each is good for and what you need, and how to choose what method works best for you. âUsing straight-line distanceâ is the simplest way of finding whatâs nearby, by either creating a buffer to defined a boundary and find whatâs inside it, select features to find others within a given distance, calculate feature to feature distance to find and assign distance to locations near a source, or create a surface to calculate continuous distance, and each method is discussed in depth. âMeasuring distance or cost over a networkâ is a method where the GIS identifies all lines within a given distance, time, or cost of a source location, by specifying the network layer, what the GIS does, assigning street segments to center, setting travel parameters, specifying more than one center, and selecting the surrounding features to make the map. âCalculating the cost over a geographic surfaceâ lets you find whatâs nearby when traveling overland by creating a raster layer with the value of each cell being the total travel cost from the nearest source cell, and how and why to do this.