Andy Mitchell- ESRI ® Guide to GIS Analysis chapter 4-6

Chapter 4- Mapping density

Mapping the density of features lets you see the patterns of where things are concentrate.  This allows you to find areas that require action or mointore changing condisitons. Density maps are useful in looking at patterns rather than looking at locations of individual features or mapping by size. Census tracts or counties are espesially useful as density maps.  There are a few ways to map density, as this chapter describes.  One way is to shade definded areas based on density value.  Before you actually do your mapping, it is important to think about the features you are mapping.  This chapter describes in a clear, interesting way to map density. From the way they explained this, it seems like something that is relatively easy to compose in GIS. Chapter 5: Finding what’s Inside

Finding what’s actually inside lets you see whether an activity occurs inside an area , or summarize information for each of several areas so you can compare them. This chapter goes into depth on different ways to go inside a single area or a few areas, and determine whether extra attention needs to be taken or not.  Mitchell describes 3 ways of ‘finding what is inside’.  The first is Drawing the areas and features, in which you create a map showing the boundary of the area and the features. Second, Selecting teh Features inside the area, you specify the area and the layer containing the features, and the GIS selects a subset of the features inside the area.  Lastly, overlaying the areas and features, which GIS combines the area and the feautures to create a new layer with the attributes of  both, or compares the two layers to calculate summary statistics for each area on the fly.  They each have interesting merits.Chapter 6: Finding What is nearbyFinding what is near by lets you see what is within a set of distance or travel range of a feature. This lets you monitor events in an area, or find the area served by a facility or the features of affected by an activity.  This chapter describes methods such as straight-line distance, distance or cost over a network, and distance across a surface.  These applications seem to be very important in determining how far away thingd are.  This is a great chapter in allowing the readers to understand the different methods as well as a lot of very helpful features.