CHAPTER 4
density maps are something I have always taken an interest in, particularly in the ecological field. It’s always interesting to see the population density maps of local species. I also don’t usually think of density maps like the book demonstrated. They use business density instead of points. The book gives a great definition of when to use mapping density; ” mapping density is especially useful. Mapping density is especially useful when mapping areas such as census tracks or countries that vary greatly in size. As mentioned previously, this is how I viewed density maps. The color gradient makes density maps easy to follow and understand. The map Mitchell uses to show logging roads on page 108 does an efficient job at showing the density of the logging roads. However, it is confusing to follow. While reading, I was initially confused about the difference between map features or feature values. The book defines features as locations of businesses and feature values as the number of employees at each business. The visual figure on page 109 does a good job of demonstrating the differences, leaving me with no further questions on the differences. My previous understanding of density maps was strictly limited to the color gradient style that we are most familiar with. While reading Mitchell’s book, I was informed on the use of density maps as dot maps for this example. They still use businesses but one dot equals five businesses to show the density. One interesting point about dot maps was the dogs are distributed randomly within each area. They don’t represent an actual feature location however, the closer that together the dots are the higher density of features in that area.
CHAPTER 5
Chapter 5 is about why map what’s inside. Mitchell says on page 134 by monitoring what’s going on in an area, people know whether to take action. He uses the example of a district attorney who would monitor drug related to arrests to find out if an arrest within 1000 feet of a school if the arrest occurred within 1000 feet, stiffer penalties would be applied. The nice part about the density map that I learned about is you can find out what’s inside a single area or inside of several areas. When I originally read about surveying multiple areas, I was initially confused about the logistics behind it, but the book uses a great example, such as ZIP Codes or watersheds. The book has a good section on whether the features inside the map are discreet or continuous. It goes on to describe discreet features as unique, identifiable features you can list, count, or summarize. A numeric attribute is associated with them. Continuous features represent seamless geographic phenomena. The example the book uses is especially continuous categories or classes such as vegetation type or elevation range *topographical maps. The section on page 147 under comparing methods was extremely insightful. While reading through chapter 5 i found myself wondering when to use which methods the three-layered tables lay out all three methods: drawing areas and features, selecting the features inside the area, and overlay the areas in features. Was extremely useful on what each method is good for the types of features that uses and the trade-offs associated with them. another thing I found interesting in Chapter 5 was the ability to take the data from the map and put it on paper. a count is the total number of features inside the area. this was taking was we collected and allows us to use it in a data set.
CHAPTER 6
As I read in chapter 6, I think all of the learning objectives which were: Y map what’s nearby, defining your analysis, three ways of finding what’s nearby, using straight line distance, measuring distance, or cost over a network, calculating cost over a geographic surface were addressed fully and to the greatest extent. The first section wide map what’s nearby was extremely applicable to your daily life as they mentioned you can find out what’s occurring within the set distance. You could also find out what’s within traveling range. One thing I wouldn’t have thought to take into account about measuring distance was measuring flat plane, or the curvature of the earth. A recurring concept that we have seen through all six chapters now was needing to know the specific information you are looking for from the analysis i.e. do you need a list count or summary? Once again, I found the comparing methods table to be extremely useful a compared the three methods straight line distance, distance or cost over a network, and cost over surface. The table gave the appropriate uses the rhyming features. You should look for the measures the pros and the cons and the very next section called choosing a method put the table into action and made it very straightforward. Much later in the chapter 6, it gets very in depth on making maps using distance using costs how arc GIS works specifying network layers stops, and turns travel parameters. It’s quite impressive. How much computing you can have arcGIS do.