VanderVelde – Week 3

Chapter 5: 

Chapter 5 focuses on why map what’s inside, defining your analysis, 3 ways of finding what’s inside, drawing areas and features, selecting features inside an area, overlaying areas and features. why map what’s inside an area is to monitor whats occurring inside or to compare the area to other areas. Defining your analysis is to find what is inside an area by either drawing a boundary on top of features, using an area boundary to select features or list the features and summarize. To do this you need to know how many areas you have within your data, are the features discrete or continuous. continuous features are seamless geographic phenomena and can be summarized like soil type and precipitation. What information is needed for an analysis like is it a count, list or summary? And do you need to see the features that are only within the area or can features that are partly within an area be counted/ used. 3 ways of finding whats inside are drawing areas and features, selecting the features inside of the area and overlaying the area and features. Drawing is good for finding if features are inside of an area but are visual only = no information. Selecting the features inside of the area is good for getting a list or summary of all the features within an area but does not tell you whats inside each of the several areas. Overlaying the areas and features finds out which features are inside and summarize how many features by area but requires more work/processing. Drawing areas and features uses GIS to draw on top of features making discrete features see-able and allowing for a sense of the range of continuous values to be made. Selecting the features inside an Area is a method to specify the features and the area. The system checks to see if each feature is within the area, and selects the corresponding rows of data to feature inn the data table. To use this data you can create a report on the selected features with a count, frequency or summary of the numeric attributes per the features. overlaying the features and areas is a method to find discrete features and summarize, calc the continuous categories or class inside one or more areas. This is done with overlaying the areas with discrete features or overlaying the  areas with continuous categories or classes.

Chapter 6:

Chapter 6 focuses on why mapping what’s nearby, defining the analysis, 3 ways of finding whats nearby, using straight line distance, measuring distance or cost over network, and calculating cost over a geographic surface. why map what’s nearby is to find out what’s occurring within a set distance from a feature as well as what’s within traveling range. This can help determine areas that are sustainable/ capable of supporting a specific use. Defining your analysis is to find what is nearby and deciding how to measure nearness and what information needed for analysis to help then choose which method to use. For this we should know what are we measuring and whether its using a distance or cost. and if the distance is over flat or rough terrain. The 3 ways of finding what’s nearby is using a straight line, distance or cost over a network and cost over surface. Distance for a straight line is good for defining an area around a feature and creating a boundary around them but it only gives a rough estimate for travel distance. Distance over a cost network is for measurement travel over a fixed infrastructure but requires an accurate network layer. Cost over surface is used for measuring overland travel and calc how much area is within that travel range but requires more data prep to build the cost surface. using straight-line distance is how to see which features are within a given distance of a feature/source. Creating a buffer around this feature can be useful as well as selecting which features within the distance like a buffer but not quite. Creating a distance surface. measuring distance or cost over network is a GIS method that ID’s all the lines in a network within a given distance, time or cost of a source location. these sources are termed centers. calculating cost over a geographic surface allows for figuring out what is nearby when traveling over the land, this needs a raster layer  within each cell value of the travel cost from nearest source cell. To do this we must specify the cost, modify the cost distance, where the information is coming from should also be specified as well as summarizing whats within the distances found.

Chapter 7:

Chapter 7 focuses on why a map changes, defining your analysis, 3 ways of mapping change, creating a time series, creating a tracking map, measuring and mapping change. Why maps change is to anticipate refuter condition’s and then to decide what course of action should be taken as well as evaluation the results of an action policy. defining your analysis is for when the map does change by showing a location and condition of features at each date and then from this we can calc and map the difference in each value for each feature between the 2 dates. for this we need to know types of change, the geographic features, how to measure the time between and how it will affect the geographic patterns on the map and the information you need from the analysis. there are 3 ways of mapping change, time series, tracking map and measuring change. Time series is good for movement or change in a character but visual comparison between 2 maps must be done to comprehend. Tracking map does movement but can be hard to read if there are a lot of features. Measuring change is for a change in character but doesn’t show actual conditions at each time and the change clac between 2 times only, no more. Creating a time series but you’re making a map for several times and dates a couple of times and the need to consider how many maps and the range of values. To show a change in location, change in magnitude or character, the number of maps to show and looking at the results of all of this. Creating a tracking map shows the position of a feature(s) at several dates/time. measuring and mapping change is to calc the difference in values between 2 dates  and map features based on the value calculated. discrete features and data summarized by the area must be known. As well as continuous categories or classes with continuous numeric values.