Month: February 2023

Chapter 5

This Chapter of Mitchells, The ESRI Guide to GIS Analysis, focuses on “Finding What is Inside” of the image you are looking at. Sometimes, you only want to focus on a singular part of the image. Say for example, you have a map of types of agriculture in Ohio, but you only want to focus on Northeast Ohio. You can choose to only analyze a single area in order to get the full picture. You can also section your analysis based on things like county lines, and zip codes. You can also make this analysis discrete or continuous, like Mitchell discussed in earlier chapters. There are three ways of finding what’s inside. By 1, drawing areas and features, 2, selecting the features inside the area, and 3, overlaying the areas and features. Drawing areas and features is good for finding out whether features are inside or outside of the designated area. However, this method is not very specific, and often cannot provide the information needed for a full analysis of the map. Selecting the features within the area is good for summarizing the features inside, but it is only good for evaluating one single area, not a collection of larger areas. Overlaying the areas and features is good for finding out which features are inside, and how dense these features are. However, this process is quite extensive, and requires more processing. Mitchell also describes how it can be good for evaluating the data if layers are overlapped with discrete and continuous data. For example, you could have the discrete layers of land plots overlap with a floodplain. We can directly see which areas are being impacted. We can also do it inversely, by mapping continuous data of types of land, and over laying boundary lines over it. With these overlapping boundaries, you can then get a list of attributes of a given area within the image, whether its number of people, number of species, density of population, etc. We can overlay boundaries in GIS using either a vector or a raster model to ensure that all variables are both together in an image and sorted separately. The vector model is almost the overlaying of 3 separate images mapping different variables, and putting them all together. The raster model is the sort of “cookie cutter” image going into a figure to display the area of interest. 

 

Chapter 6 

This Chapter of Mitchells, The ESRI Guide to GIS Analysis, focuses on “Finding What’s Nearby”. This is useful for knowing what is in the general area of the location you are concerned with, and if surrounding areas could be impacted by what you are surveying. For example, we could look at nearby floodplains that are near a body of water that are at risk of floods, or houses near intersections of the highway that could be susceptible to effects of eminent domain. Measuring how near something is can be used in distance, or in cost, or “travel costs”. If something is very far away from the desired location, things like heavy traffic and gas prices could be a barrier of distance. For example, if you are mapping how close streets and homes are to a fire station, the streets that are within ¾ of a mile, and are within a 3 minute drive of the fire station represent very different parts of the town. You also need to account for the size of the area you are looking at. For smaller areas, you can look at this on a planar method. But if you are looking at something larger like a continent or the world, then you need to use a geodesic method, based on the curve of the earth. You are able to summarize what is within this nearby area and turn these variables into quantified data as well. You should use the straight line distance method “if you are defining an area of influence or want a quick estimate of travel range”.  You should use the cost or distance method if you are “measuring travel over a fixed infrastructure to or from a source.” You should use the cost over a surface if you are measuring overland travel. It is also helpful to use color coding legends in the figure to depict the distance from the point you are evaluating. 

 

Chapter 7 

This final chapter of Mitchells, The ESRI Guide to GIS Analysis, focuses on “Mapping Change”. This section specifically focuses on how to represent data of change over time, and how the characteristics of the area change as time progresses. An example of this, could be a representation of sea level rise over time. The first image that you show might depict sea levels in the 1950s, and then sea levels today, and then where sea levels are expected to be in the coming decades. A large reason for this according to Mitchell is to “anticipate future needs” and to “gain insight on the behavior of a certain event or region”. You can also use mapping change to show how a certain object or thing is moving locations over time – an example of this might be a representation of how the migration patterns of certain bird species are evolving due to the changing climate and weather patterns. This might show us two completely different regions of the world, but is still mapping the change in some variables. You can represent a change in a figure through three different types of time patterns: a trend – a change between two (or more) dates and times, before and after – conditions preceding and following an event, or a cycle – change over a recurring time period such as a day, month, or year. However, you do not want to use too broad of a time frame, nor do you want to use too many data points of comparison, because the main difference between the change in figures might be lost, and the message of the data may not be as clear as you desired. Mapping the change in a set of data is very important in order to understand how we are evolving, and what the trends are for future expectations.

Chapter Five:

Chapter five focuses on mapping what’s inside a particular area. In the broad spectrum of things, this idea of mapping what’s inside seemed a bit irrelevant to me, but the chapter made it seem very important. People map what’s inside an area to monitor or to compare several areas to each other. It becomes easier for people to know whether to take action by observing what’s occurring in a region. The chapter also mentions that the first thing that we need to do is define our analysis and identify the type of our data. We can choose a single area or multiple areas for analysis. I think in places like India, where areas are divided into multiple sections(like pavements), it might be easier to get started with a single one and then move to multiple regions. Multiple areas include continuous (geographic phenomena) and discrete(unique, identifiable), like zipcodes and state parks. The mathematical terms, like list, summary, and count, used in Chapter three were also mentioned here as a way to use GIS to analyze information. Another thing the user can choose is whether to include features that fall completely outside/inside or partially a part of the area boundary. We can use GIS to overlay the protected area and the land cover areas.

Mitchell mentions the three ways of finding what’s inside, namely:

• Drawing areas and futures.

• Selecting the features inside the area. 

• Overlaying the areas and climate. 

Initially, each one of them is divided into their pros and cons using the compare table shown in chapter three. The chapter then elaborates on these three types throughout till the end and how they are related to discrete features. frequency, count, and how their results can be used. 

 

Chapter Six: 

 

Chapter six focuses on what’s nearby. Similar to chapter five, it goes in on the importance of certain aspects of geographic locations. GIS helps find out what’s occurring within a set distance of a feature. It helps identify the area and the elements inside that area that are affected by an event or an activity. Finding a traveling range which is measured using distance, time, or cost, helps define an area served by a facility. The chapter starts by asking the reader to define their analysis and identify their type of data. The author mentions that it’s also essential to choose if “what’s nearby” is set by distance or some other range. Distance is one way of deciding nearness, but it can also be measured using cost. In my mind, the word cost is always associated with money, but here it is used for time. One of the interesting things mentioned in the textbook is choosing whether to use a flat plane or use the curvature of the earth. 

The terms list, count, and summary from chapter three were mentioned again here to help the reader choose the best method of analysis. Distance and cost can be single or multiple ranges. Multiple ranges can either use inclusive rings or distinct bands. Like chapter five, There are three ways to find what’s nearby: 

• Straight line distance — Specifying the source feature and distance
• Distance or cost over a network — Specifying the source locations and a distance or travel cost along each linear feature. 
• Cost over a surface — Specifying the location of source features and a travel cost. 

The pros and cons are also mentioned to compare the methods and choose whatever is best for the reader. These three types were then further elaborated throughout the end by mentioning their subtypes and instructions, how GIS can be used for this, and how the result obtained can be analyzed. To me, this chapter was heavily similar to chapter five in the way it was structured. 

Chapter Seven:

Chapter seven focuses on mapping the change. Mapping change is very important as it helps find predictions that can be further used to take action. My TPG Draft Proposal Project for ENVS110 was based on predicting change(flood risk), so additional policies could be made to protect marginalized communities. To define the analysis, we need to understand the types of change. Geographic features can change in location or magnitude. Change in the location usually helps us see how features behave so we can predict where they will move next, for example, by forecasting hurricane patterns. Change in magnitude helps understand how conditions in a particular place have changed, for example, to observe land cover or vegetation in an area. Knowing the type of feature also helps choose the best method for mapping. There are two types of features — features that move and features that change in character or magnitude. Discrete features that can be tracked as they move through space and events that represent geographic phenomena are the two subtypes of moving features. Discrete features that change in the quantity of an attribute associated with them, Data summarized by areas that are quantities are associated with features within a defined area, Continous categories that show the type of features in a place, Continous values that are continuous quantities, for example, pollution levels, these are all subtypes of magnitude changing features. Three types of time patterns can be measured: 

• A trend that indicates whether something is increasing or decreasing. 
• Mapping conditions before and after an event lets us see the impact. 
•  Cycles show recurring patterns that reveal information about the behavior of the features. 

A snapshot or a summary can be used to display feature locations or characteristics two or more times. To map trends, determining an interval, the number of dates, and the total period can help. It is important to know how much and how fast the magnitude has changed after the analysis. There are three ways of mapping change: 

• Time Series – Good for showing the change in boundaries, values for discrete values or surfaces 
• Tracking Map – Good for showing movement in discrete locations, linear features, or area boundaries. 
• Measuring Change — Good for showing the amount, percentage, rate, or place. 

Similar to chapter five, the methods were laid down in a comparison table with their pros and cons to help the reader choose the best method for themselves. Next, the chapter gave instructions on creating a time series by showing the change in character or location. To create a tracking map, we can map individual features, linear features, contiguous features, or events. To measure and map changes types of character-changing features can be used. The chapter provides detailed instructions even for complicated situations, like mapping when there are negative values or if the boundary or category of definitions has changed.                                                              

 

Chapter 5: 

Chapter 5 deals with mapping what’s on the inside a designated area. Sometimes you will already have boundaries available in ArcMap but other times you will need to draw this area or areas on top of the features manually. The chapter lists several reasons you might want to map data inside a boundary, but as always it is important to keep in mind what you are trying to accomplish and how that will affect your approach. Mapping a single area will be different than mapping multiple areas while handling discrete or continuous data will affect your approach. Mitchell also notes that it is important to have some type of label whether it is a number or a unique name for each area mapped. The three ways of finding what’s inside are described as drawing areas and features, selecting the features inside an area, and overlaying the areas and features. Drawing areas and features are the easiest and most simple method, but it really only gives you a visual representation and not information about the features inside. Selecting the features inside an area allows you to get info on what is happening in a single area, but you are not able to see what is happening in each of several areas. For example, a map of parcels within a watershed using this method will let you see which parcels are within the watershed, but may not distinguish the type of parcels. With this method, you can use GIS to create a report of the selected features or statistical summaries. This data can come in the form of a count, frequency, or as a summary of a numeric value (i.e. sum, average, median, or standard deviation). Overlaying the areas and features avoids this by allowing you to see what is within each of several areas (i.e. parcel type), but it requires more time and processing than the other methods. Overall, I really liked this chapter and the examples provided. 

Chapter 6:

Chapter 6 deals with mapping what’s nearby a feature. There are many reasons why you might want to find out what is occurring within a set distance of a feature or to find out what is within traveling range. Reasons could involve legal policy decisions, business or environmental precautions, or simply a scientific analysis of an area. While distance can define or measure the proximity or features, travel costs may also be used. Travel costs, which may include time and money, may vary even if the distance between a set of features is the same due to other factors. For instance, it will cost a car more gas money to traverse a highly trafficked area rather than a relatively low trafficked area. It would also take less time for a deer to cross a valley to get to a stream than it would to cross a deeply forested area. In this way, the valley has a lower travel cost. Something to keep in mind is whether you are considering the curvature of the earth in your distance calculations or not. The planar method is used for smaller areas that can generally be observed as flat, while the geodesic method is used for larger areas where the curvature of the earth is taken into account. You may not think the curvature of the earth would need to be considered when dealing with relatively small areas, but major bridge constructions sometimes have to account for the earth’s curvature as the tips of supporting structures will be further apart from each other than they are at their respective bases. Information from an analysis can come in the form of a list, a count, or a summary of statistics.The reading describes three ways of finding what’s nearby: straight line distance, distance or cost over a network, and cost over a surface. As always, each method has its own uses, pros, and cons. Straight-line distance is used for defining areas of influence near a feature or selecting features at a set distance around a source, which gives an approximation of travel distance. Distance or cost over a network measures travel distance or cost of location over a fixed network or infrastructure, but requires a network layer. Cost over a surface is used for measuring overland travel costs and determines how much area is within the travel range. The rest of the chapter goes over these methods and guides you through making and modifying distance maps. Overall, I liked this chapter even though distance cost was a new concept for me. The chapter does a good job of describing why it might be important to calculate the distance between features (with the respect of area). 

Chapter 7:

Chapter 7 informs why it may be important to map change over time. Mapping changes over time is one of my favorite uses of GIS technology as it can be applied to countless environmental questions. Mapping changes over time is a great way to visualize patterns and predict future changes. This could involve examining weather patterns, changes in land use, or changes in population density. When mapping change it is important to remember the types of changes that exist. For instance, the book outlines changes in location, character, or magnitude, which all can describe geographic phenomena. Recognizing the types of features, such as discrete or continuous, is vital for choosing the appropriate method to map change. Measuring the time pattern is also key to mapping change. The three types of time patterns described are trends, before and after events, and cycles. Snapshots may be used to capture a set of conditions at one point in time, such as land cover or population data. Summarizing can be used to map discrete events that are not continuous in time. An example of this would be summarizing the daily precipitation for a region into monthly averages, which may show trends in weather patterns and may allude to the overall climate of the region. When mapping trends it is necessary to consider intervals, the number of dates, or total period. For instance, depicting urban sprawl annually may have as much of an impact when comparing the sprawl across several decades. For mapping cycles, a snapshot or summarization over a period can be used depending on whether the data is continuous or discrete. The chapter also lists three ways of mapping change. A time series is good for depicting changes in boundaries, surfaces, or values of discrete areas, which can lead to a strong visual impact. Tracking maps are great for showing movement in discrete locations, area boundaries, or linear features. These maps can become cluttered and difficult to read if there are more than a few features. The measuring change method involves showing the actual difference in values or amounts between two times only. This type of map only shows the change and not the actual conditions at either time. The rest of the chapter delves deeper into these methodologies and how to apply them appropriately. In conclusion, I don’t think the book could have ended on a better chapter since the earth and its features are constantly changing. As human beings, we are fascinated by change, so being able to map change is really rewarding and can lead to new insights to our behavior and geographical phenomena.

Chapter 5:

Chapter 5 built off a lot of what was learned in chapters 1-4. It reaffirms the importance of knowing whether your features are continuous or discrete when mapping. Mitchell notes that when dealing with discrete areas you can represent features with several different methods. This includes drawing boundaries on top of each other, on top of a color-coded area, or shading and labeling the boundaries. The reading then details for continuous features you should draw areas symbolized by category and quantity and then draw the boundary on top. I think the difference here is important as continuous data must be represented differently, in this way almost separately for the map to accurately show features and help the viewer get a sense of the range of continuous values.

The chapter then goes on to talk about what kind of data you can get from maps like lists and summary statistics before it gets into what I thought was the most important part of the chapter. This was the portion discussing overlaying areas and features. I talked about two different methods of doing this – the vector method and the raster method – this reaffirmed the difference between vector and raster layers while providing a new mechanism for producing maps and representing features. Briefly, with vector overlay splits category or class boundaries where they cross areas and create a new dataset with resulting areas. Vector is more precise, but it has one problem – slivers. As I understand it, slivers are where borders are offset. If these slivers are so small, it is important to merge them with surrounding data. This brings us to the raster overlay. Raster overlay combines raster layers and counts the number of cells in each category within each area then calculates aerial extent by multiplying the number of cells by the area of a call. This can ultimately be less efficient depending on cell size, but it does prevent slivers.

 

Chapter 6:

Chapter 6 was all about finding out what’s near and relevant to your feature(s). It talks about how travel is often measured by cost, which is time, money, effort (referred to as travel costs), and distance. The chapter then moved on to outline 3 different ways to find what’s nearby. The first and probably simplest of these is straight-line distance. Essentially, given a source feature and distance, the GIS will find features within the distance. The next method is distance or cost over a network in which GIS finds segments within the distance or cost given source locations and a distance or travel cost along each linear feature. Finally, there is cost over a surface in which you specify the location of the source feature and a travel cost, GIS creates a new layer showing the travel cost from each source feature.

This brings us to some new vocabulary from the chapter. First off, source locations are often referred to as centers. An impedance value is the cost to travel between the center and surrounding locations. Edges are lines, Junctions are where edges meet, and turns are used to specify the cost to travel through a junction check that these exist, are correct, and are in the right spot. These all help to define the network layer.

Another part of defining the network layer is cost. You can specify street direction or more than one center (rural vs urban areas) as these details can change the cost by lengthening travel. The GIS also checks and tags each distance of each segment keeping a cumulative total of cost or distance. One thing I did not understand about cost was the calculation. To find the monetary value the book gives the equation of Cents = length*(cost per mile/5280), but I feel as though travel costs are dependent on many other factors like traffic, gas prices, etc. So, I am slightly confused about how the given cost is an accurate reflection without some way of factoring those in.

 

Chapter 7:

Chapter 7 discussed mapping changes over time and how it can help predict future needs. It talked about mapping features previously discussed such as discrete features, data summarized by area, continuous categories, and continuous values. Specifically, it talked about how these features can change in character and magnitude. A change in character might be something like a physical movement of a feature, whereas a change in magnitude might be something like a hurricane or storm getting “worse” or “better”.

The chapter then moves on to talk about time. There are 3 ways to measure time: trends, before and after, and cycles. A trend is a change between 2 or more dates and times. This shows increases, decreases, and direction of movement. Before and after are conditions preceding and following an event. This lets you see the event’s impact. Finally, a cycle shows change over a recurring period and can give about the behavior of the features you are mapping. There are two ways to represent these changes in time as well. The first is a snapshot, which shows the condition at any given moment and is used to map continuous phenomena. The second is a summary where an event either is or isn’t occurring at a given time and is used for mapping discrete events. For cycles, you can use a snapshot or summary, for discrete events use a summary, and for continuous data use a snapshot.

The final portion of the chapter discussed the 3 ways of mapping time. The first is a time series. This represents movement or change in character. It can use a trend, cycle, before and after, and shows conditions at each date/time, but it can be hard for readers to compare visually. You should use this for a snapshot when you have 2 or more times. The second is a tracking map which is used for movement and can represent a trend, cycle, or before and after. It is easier to see subtle movement but can be difficult to read if there are many features. You should use this method when you have feature movement over 2 or more times. Finally, Measuring Change measures a change in character. This can represent a trend or before and after and shows the actual difference in amounts or values. However, it doesn’t show any actual conditions and only uses 2 times. The chapter then goes into thorough detail on the process of creating each of these maps. Overall, I thought this chapter was straightforward and I don’t have any questions about it.

Chapter 5:

Mapping what’s inside can be used to decide if action needs to be taken. For example in times of emergencies, maps can be used to show what areas are at risk. You can also use multiple maps to compare what is “inside” of different areas. Using an area boundary allows you to select features that you will be mapping and therefore create the “stuff” that you are mapping inside. Understanding your data is once again an important part of the process of mapping what’s inside. You must know whether you are mapping what’s inside a single area or several areas, because this will affect how to best map the data. If it’s a single area you can easily monitor activity or summarize information within that area. If it’s multiple areas, you can see how much of a specific thing is specific areas and compare them. There are also three different ways to find what’s inside an area, drawing areas and features, selecting the features inside the area, and overlaying the areas and features. Drawing areas and features allows you to find out whether features exist within the area or not, but only give you surface level information (you can’t get information about the features inside an area). Selecting the features inside the area results in a list or summary of features inside an area, but doesn’t separate information by area (you only get a list of features inside all areas combined together). Overlaying the areas and features allows you to find out which features are inside each area, and summarizes how many or how much is in each area. This gets the most expansive information, and solves the issues from the other two methods, but takes the most time and effort processing. The choosing a method section on page 148 will be useful for choosing a method if I ever have to do this in the future. The section on selecting features inside an area shows a bunch of example maps that look to me like they show the data very well and are “good” maps. The map and section on page 177 about overlaying areas with continuous values is really cool. I like the way that the GIS is able to combine elevation surface and a watershed layer and show how the elevation and watershed mesh together.

Chapter 6:

This chapter highlights why it can be important to map what’s nearby. Traveling range is an important component of doing this, and is defined by distance, time, and cost. Understanding what’s within the traveling range of an area can help you better understand how that area can be used and serve important purposes. The first step in the process of mapping what’s nearby is figuring out how to define and measure “near”. Making a definition like this feels important because “near” can mean a lot of things and a baseline definition would make things a lot easier. This nearness can be defined by either a set measurable distance, or by travel to and from a specific feature. You can find what’s nearby using straight-line distance,  or by measure cost over a network or over a surface. Using straight-line distance is the simplest and in my opinion most intuitive. Cost over a network and over a surface seemingly gets more complicated and involves more thinking/understanding. Useful ways to choose a method are found on page 191 and involve thinking about if you can define an area of influence, need a quick estimate of travel time, are measuring travel over fixed infrastructure, or are measuring overland travel. I think the way that you can use straight-line distance around a specific feature to find distance is really cool. I liked the example map of the selected parcels surrounding or within 100 feet of the road. I also think creating a buffer feature could be really useful and is something I’d like to practice doing. Once you have point-to-point information, you can create a map that color-codes locations by distance from the source (and closest to the source), make a spider diagram, or map source features using graduated point symbols. A spider diagram is when the GIS draws a line between each location and the nearest source. You can do this with multiple different sources and create a map that resembles a multicolored spider-web, comparing and representing the different patterns between source features.

Chapter 7:

Mapping change feels like a different thing than what we’ve been reading about because it’s a future phenomenon. This can be useful because it allows people to anticipate future conditions. You’re able to map expected conditions by looking at historical conditions and to eventually anticipate future needs. In order to best map change, you need to understand the types of features you are mapping. Features that move can be mapped using discrete features. These features can be tracked as they move through space. They include features you can map paths for (like hurricanes, a vehicle or animal), linear features (like a changing stream channel), or an area feature (like a fire boundary or oil spill). You can map change in three ways, time series, single tracking map, or map the differences in values between two times or dates. Time series show movement or change in character and have a strong visual impact. Tracking maps show movement and better show subtle change. Mapping change shows changes in character and shows the actual difference in amounts or values. If you generate multiple maps over different dates, it can be important to correctly decide the number of maps to show. By showing fewer maps, farther apart in time you can make the change in values easier to show, but less nuanced. Showing a bunch of maps with dates more closely together in time, you can reveal more detailed patterns about the change. Also, it can be helpful to include tables and charts that summarize data along with your maps. A tracking map is a map where the movement of individual features is mapped using a series of contiguous points. You can add a line connected points to emphasize the path the feature followed or even map the points at equal intervals to see how far the feature moved in a set time. Mapping continuous categories or classes is more complicated than mapping other features because it involves combining two layers, for both date and time. I get a little bit confused when it starts talking about raster data and areal extent. I feel like I’m going to have to do some more reading and investigating to understand this.

Chapter 5:
When mapping some people want to define what’s inside of an area to compare two sites or to see what’s inside a single area. A single area allows you to summarize data found inside or monitor the activity going on inside, whereas multiple areas allow for a better comparison between locations. Discrete features are those that are unique and continuous features are those that are seamless that can be summarized for a whole area. There are three types of information you can obtain a list, count, or a summary which wholely depends on the information needed. Some features may be partially inside of an area so you may exclude them in the case of a summary but in a list or count you will want to include them. Drawing areas are good to see a few features within a selected location. Selecting features is good for lists or summaries within a selected area. Overlaying both of these data is a combination and is good when comparing more than one area. Once all of the above has been considered the next step is drawing the map. If you are mapping linear features you can use a single symbol by creating a category. Discrete locations depend on whether your focus is on the inside of the location or just the area itself, but you will want to label these features. If mapping continuous features you will want to map the data and then place the area lines over top to separate the inside from the outside. In some GIS software, you will be able to select locations within the area and highlight them which can allow for better analysis. When doing your analysis you can count, find the frequency, or summarize a numeric attribute. Maps using areas with discrete features can use a linear model whereas maps using continuous features have to use a vector or raster model to show the data.

Chapter 6:
When mapping in GIS you may want to find what’s nearby to a location to find what’s within a certain distance which can be used by planners. To define nearness you can set a distance or a specific location. In a set distance the data is linear whereas a specific location or time is found to be geometric data defined by data limits on your map. When mapping distance curvature of the Earth can be chosen to be included or not depending on the creator of the map and the data. Much like the last chapter since the data being mapped is an area the information that is needed can be found in a list, count, or summary. Inclusive rings are when all the data within a range is included whereas distinct bands show data differently within each band. Straight-line distance is good for finding what’s within a boundary, distance or cost network is good for finding data that follow a linear path, or cost over a surface which is good for calculating overland travel. In a straight-line distance model, you will need to create a buffer to define your area and select the data you will want. In a distance surface model, you will use a raster model where each cell could have a potentially unique value. In a distance or cost network, the GIS software used will have an updated street map you will use but also will need you to define the layer used and the center starting point. Much like the distance over the surface model, the cost over surface model uses a raster model but each cell would define a certain cost rather than the distance from the center point.

Chapter 7:
Mapping allows you to better predict the future by seeing where things have been and predicting where they could be going. There are two types of change being mapped, location and magnitude both of these can be discrete or continuous. Time can be measured as a trend, before and after, or a cycle these each can be used for different analyses. Snapshots show the conditions in a given moment of time whereas summarizing is showing discrete events that are happening or not. When mapping trends you will need to set dates and intervals which may already be defined by the data you have collected or you will need to set them yourself. When doing your analysis you either calculate their amount or rate of change. A time series is used to show the changes in boundaries, a tracking map shows the movement in discrete locations, and measuring change shows the amount of change in a place.

Chapter 5 finding what’s inside

This chapter is about finding what’s inside. It seems like a simple concept that most people understand but don’t often put into words. Looking at what is occurring inside an area can help identify problems and monitor what’s happening within the area and compared to other areas.

More technically this chapter is about using GIS to list, count, summarize, or view features within area boundaries. There are 2 types of boundaries. They can be contiguous(when one area stops another starts) or disjunct (disjointed and distinct). There are 2 types of features. They can be Discrete(unique, identifiable, and able to be listed or summarize a numeric attribute) or continuous(seamless geographic phenomena and able to summarize the features for each area). There are 3 ways to use GIS to identify features within an area. Drawing areas and features is a visual approach  that is good for seeing the features and the boundaries. Selecting the features inside the area is when you select an area and the GIS finds the features within the area. It is good for getting a list or summary of features inside an area. Overlaying the area and features compares layers and is good for finding which features are in several areas or the quantity of a feature is in one or more areas.  

The chapter then goes into the actual processes behind creating the map. It includes how, why, and when to use different combinations of line, area , and feature types. It adds details on the ways the results can be shown.  Included there are many helpful tips and I enjoyed the detailed breakdown on the processes . This portion will be useful to return back to once I have hands on experience and use as a guide when creating maps. However, currently I cannot put this information into practice.

Chapter 6

This chapter is about what is occurring within a set distance from a feature. Similarly to last chapter this helps monitor activity. It is important to note that the area is identified by the feature.

The GIS is used to list, count, summarize, or a range (distance/cost) . The GIS can define the area boundary by using 3 methods. Straight line distance is a rigid way to see features within a set distance. Cost over surface is good for calculating overland travel cost.  Distance or cost over a network is good for finding what’s within a travel distance or cost over a fixed network. The cost can be based on time, money, or effort. There are 2 ways to measure distance. The Planar method does not account for the curvature of the earth and is good for measuring over short distance. The Geodesic method takes into account the curvature of the earth and is good for measuring over large distances. There are 2 ways to utilize the area boundary created. Inclusive rings are good for finding totals of one feature within the boundary as the distance increases. Distinct bands are used for comparing distances from a feature.

The chapter goes into details about the methods in practice. Creating a buffer can be a temporary or the number of  permeant way to find what’s within a set distance of the feature. The buffers can be used for one or more features at once. Similarly to the last chapter this will be a nice reference point when I begin using GIS software. The overviews of the concepts made sense. The more technical portion of this chapter should make more sense with time.

Chapter 7

This chapter discuses using maps to track change. Tracking change is useful to predict the future, decide on an action, or generally gain insight into an area.

There are 2 types of change that can be mapped. There are changes in location(using past movement to predict where it will move) and changes in character or magnitude(shows the change of conditions for an area).  There are 2 features that move: Discrete features and events. there are 4 features that change in character or magnitude: discrete features, data summarized by area, continuous categories, and continuous values. There are 3 ways to measure time. They are trends(change between two or more dates or times),before and after (conditions prior and preceding an event), cycles(change over a recurring time period).  The data can be displayed in a snapshot or summary. There are 3 ways to map change. Time series is when you create one map for each time or date. Tracking maps  is when you create a single map showing the location of a feature over time. Measuring change  is when you calculate the difference in the amount of a category or a value of a numeric attribute and then display the features based on the values.

The rest of the chapter gets into the specifics of positives and negatives of all methods mentioned and the same ‘how to’ present in the other chapters. I enjoyed the examples that they added when describing the how to map. The examples stick in my head more than the descriptions. I also find that I just really enjoy maps! I have always like statistics and the maps described in this chapter remind me of a visual version of statistics.

 

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.

Chapter 5: Finding What’s Inside

This chapter discusses why “finding what’s inside” lets you see whether an activity occurs inside an area or how to summarize the information to compare what is inside several areas. By monitoring and mapping what’s inside an area, it will inform people if action needs to be taken. An area boundary can be drawn on top of the features within a single area or several areas. Within these boundaries, there can be discrete features (unique and identifiable features) or continuous features (seamless geographic phenomena). There are also three ways of finding what’s inside by drawing areas and features(a map displaying the boundary area and features), selecting the features within the area (list of features in area), and overlaying the areas and features (patterns in features found in areas). GIS can be used to draw the area(s) on top of features to gain a sense of the discrete or continuous features within, as well as checking the location of each feature to see if it’s inside the area. A helpful tool to keep in mind is GIS can create a report of selected features through statistical summaries, creating a count (the number of features inside an area), and a frequency (the number of features within a given value). Overlaying areas and features lets you find discrete features and summarize them, calculate the amount of continuous categories or summarize continuous values.
A lot of this chapter felt repetitive and could have been condensed probably. I did however get a good understanding of mapping an area in order to find valuable information inside it. Most of the time, GIS is being used to target an area being studied so “finding what’s inside” seems like a way of saying “using GIS to find trends in the study area”.

Chapter 6: Finding What’s Nearby

Chapter 6 discusses how in finding out what’s nearby, you can see what’s within a set distance or range of a feature. The information you need to complete an analysis of what’s nearby involving a list, count, or summary. If you have more than one range that needs to be accounted for, inclusive rings or distinct bands can be used. In order to find out what’s nearby, you can measure either straight-line distance, measure distance or cost over network, or measure cost over surface. Straight-line distance can create a boundary/selecting features within a set distance from a source. This can be done by creating buffers to define a boundary to see what’s inside of it, or features can be selected to find other features within a given distance. Distance or cost over a network can be used for finding what is within a travel distance or cost of a location over a fixed network. For this approach, GIS can identify all of the lines in network (ex: streets, pipelines) within a given distance, time, or cost of a location. Cost over surface can be used to calculate what is nearby when traveling over land. When using this method, GIS creates a raster layer so the value of each cell is the total travel cost from the nearest source cell. In doing so, calculating the cost over a surface can show the rate of change and patterns.
I can see why it is important to find features nearby to help find patterns in the data that you are analyzing. I also appreciated how the chapter outlined clearly what each method should be used for and how, as well as the pros and cons of each.

Chapter 7: Mapping Change

Chapter 7 focuses on how GIS can help map changing conditions to an area over time since things are constantly changing. We map change to anticipate future conditions, decide on a course of action, or articulate the results of an action/policy. In order to map change, it’s important to understand the type of features and the type of change that can aid you in the process of mapping the change. Types of change outlined in the chapter included changes in geographic features, location, and character or magnitude. These involve discrete features that physically move or have gone through geographic phenomena. We can also measure the length of time between changes with three different patterns: a trend, before and after, and a cycle. Important to keep in mind when mapping change is instead of mapping the conditions over two different times, calculate a change in value as it highlights the features that have gone through the most or least changes. There are also three main ways of mapping change outlined in the chapter. First is through a time series for seeing changes in boundaries, values for discrete areas, or surfaces. The second way is through a tracking map which shows movement in discrete locations, linear features, or area boundaries. The last method is measuring change to see the amount, percentage, or rate of change in a place. After mapping change in an area, a time series can be created to show the change over time.
Overall, mapping change is used to calculate the difference in values over time and mapping the features based on the values. Land is constantly changing, naturally and by human interaction so mapping change is important as we analyze land in the past, present, and future.

Chapter 5

Chapter five teaches about “finding what’s inside” and how it lets you see whether an activity occurs inside an area or summarized information. When paired with multiple areas, you can compare them to see patterns and information that you weren’t able to see beforehand. The main focus of this chapter was discussing boundaries that can isolate locations or information to create summary data. You can do this with a single area, which allows you to summarize information and monitor the area. You can also set boundaries on several areas that you would then treat as one. An example Mitchell uses for setting a boundary around multiple locations is if you want to find out the number of businesses within a group of zip codes. It’s important to know that you’ll want to be able to identify each area uniquely, or else you or your audience wouldn’t be able to understand the information presented. You can do this by using names or even numbers to set one area apart from another. Mitchell then talks about using counts, lists, and summaries within a boundary to gather all of the features that you’re looking for within a boundary. Another important factor in mapping with boundaries is whether you decide to include only features that are completely inside your boundary, or if you want to include features outside as well. It’s effective if you choose the latter to use different colors to distinguish the features inside from the ones outside. There are also many methods to go about mapping what’s inside; drawing areas and features is good for finding out whether features are inside or outside an area, selecting the features inside the area is good for getting a list or summary of features inside an area, overlaying areas and features is good for summarizing how many or how much by area. As with the rest of this book, this chapter provides a list of ways to map and present the information you’re studying.

Chapter 6

Chapter 6 talks about finding what’s nearby and how it lets you see what’s within a set distance or travel range of a feature, allowing you to monitor events inside an area. First, Mitchell talks about determining the style of analysis, which mainly includes travel cost and distance, but also talks about planes and whether what you’re analyzing requires taking the planet’s curvature into account. Travel range specifically is measured using distance, time, or cost: finding the traveling range of a feature can help define the area served by a facility and can help delineate areas that are suitable for, or capable of supporting, a specific use. When talking further about cost, Mitchell states that time is one of the most common costs, along with money or effort expended, in which all of these costs describe the term “travel costs”. He then talks more about calculating distance in two different ways, either assuming that the Earth is flat, or if you’re taking into account the curvature of the Earth, which are respectively known as the planar and geodesic methods. The planar method is more efficient when your area of interest is smaller, such as a city, county, or even a state. The geodesic method is more efficient when your area of interest is a large region, continent, or even the entire Earth.  The chapter then goes back to boundaries and talks about inclusive rings, which are useful for finding out how the total amount increases as the distance increases when specifying more than one area. You can also use district bands, which are useful if you want to compare distance to other characteristics in your map. From here we move on to tree different ways to find what’s nearby, straight line distance, distance/cost over a network, and cost over a surface, which all have their own intended purposes.

Chapter 7

The final chapter for Mitchell’s book talks about map changing. Map changing is when you map in GIS where things move, or the changing conditions in a place over time. Knowing what’s changed in an area, or multiple areas, is useful when understanding how things behave over time, anticipate future conditions, or evaluate the results of an action or policy. A common example of map changing is mapping the paths of hurricanes to see whether the patterns change from month to month. By mapping conditions before and after an event, you can see the impact of it, and just like in the first chapter, this helps you determine where you need to take action. I feel that defining the analysis for this kind of mapping is crucial (just like when defining analysis in other chapters) because you can either go about it by showing the location and condition of features at each date, or you can calculate and map the difference in a value for each feature between two or more dates. You can see geographic changes in location or in character or even magnitude, and choosing one or the other can alter the appearance of your map, therefore it’s important define your analysis. When mapping change by location you can see how a certain feature behaves, which can help you predict where they’ll move, and mapping change in character or magnitude shows you how conditions in a given place have changed. From here the chapter moves onto focusing on measuring by time, where it gives you a list of  ways you can measure time: by a trend (change between two or more dates/times), by “before and after” (analyzing conditions preceding and following an event), and a cycle (a change over a recurring time period, such as a day, month, or year). The chapter then talks about knowing what information you need in order to map change effectively. To me this might be the most difficult thing to learn when we start using ArcGIS more, but I’m excited to see what patterns I can create and form with map making.