In chapter 4 I learned a lot of interesting facts about mapping density and how to read maps. The main purpose of a density map is so we can compare higher concentrations of features over many locations. We measure the features and their concentrations with a uniform areal unit. These maps are super helpful when looking for correlations over a large area. Why would environmentalists want to know where things are concentrated? How do these density maps record changing conditions? Are we talking about migration or influxes of animals changing weather patterns or growing seasons? What are some of the steps that go into planning what needs to be mapped? The most important things to know before starting are all of your features and the area you want to focus on. Geographical Information Systems will map the density using a density surface. When first making a map it is important to plot the locations of interest and then find the density surface per a measurable unit like a square mile. All maps should have 2 steps first the black and white with only the targeted locations then the second map that has a color gradient showing higher and lower densities. What is the difference between features or feature values? Mapping density of features would be like the location of houses and the feature value documents many people living in the house. These maps are useful for planning roads or development efforts. A dot map is used to show density values when the map already has cluster features. This type of map makes it easier to read because they are distributed randomly. They show density geographically. To find density you divide mass (number of features) by volume (area of the polygon). Geographical Information systems will help you find density surfaces with a raster layer. It is a very detailed way to show data but also takes a lot more time.
Chapter 5 was about learning what’s inside of a map, analysis, drawing features, and creating overlay areas. The method you choose depends solely on the data you are presenting. There are a couple of different areas you could graph. A single area for example would be a town and the features would be buildings, emergency teams, or hazards reported. These maps make it easier to convey information to the community rather than using numbers and coordinates. We use GIS to predict future climate changes and how people will be affected in years to come. Discrete features are countable locations that are unique to their place of origin like roads, buildings, lakes, and home addresses. A location would be crimes and linear features are roads in a protected area like a state park. Continuous features are more complicated they are broad areas summarized there are subgroups of continuous features. Spatially continuous will tell how much of each type is in the area. Continuous values are always numeric like elevation, precipitation, road density, habitat suitability, and temperature. Will we need to make a note if we include either the whole or part of a feature if it lands partially inside a boundary? An example of a scenario when you would want to include a feature that lands partially inside a zone would be a house having a zone change. When labeling discrete features a light translucent color is ideal to show the configuration of the selected area. To distinguish areas the use of different colors is recommended to show the difference. This is all to make the map easier to see and understand. Using thick and thin lines will be helpful when making boundaries. Using GIS to select an area to be summarized first to choose the location, locations of boundaries, and distance, and the GIS will do the rest.
In Chapter 6 I learned why it’s important to map what is in range and capable of being recorded and monitored. Trying to map an area too large will only result in inaccurate data where a large section of the population is left out. A note for my future self is that traveling range is measured by cost, distance, and time. Knowing what the preferred traveling use is also helpful if it driving or walking. Areas of influence are measured using a straight-line distance of travel movement. What information will be helpful to me in the future? The count will be numerical or by type. A summary statistic is a total amount or amount by category number of acres with variable other characteristics. A statistical summary is a minimum, average, maximum, or standard deviation for example the average household size within a boundary of the local school. To get more information on distance use inclusive rings which are used to find the total amount of increases as the distance increases. Distinct bands can compare characteristics with distances. To get a more accurate measure, measuring distance over cost will be helpful. Using a ready-to-use network like ArcGIS will save time when needing to know a segment of the network and an attribute specifying its length and cost value. The cons of using a straight-line distance are it only gives an approximation of the travel distance while it is good at measuring distance quickly and easily. Distance or cost over a network is good at giving precise distance and cost but it requires a perfect network layer. To make a buffer, the line can either be temporary or permanent so that the sources can be counted. GIS will make the buffer based on either the street size or type. If you want information on the feature to feature GIS will do the calculations and find the exact distance to the source.
good! again, lots and lots of details here.