Geography 291: Geospatial Analysis with Desktop GIS

Chapter 1:

In chapter 1, some of the base information of GIS and data used for it were discussed. The general process for using GIS is detailed at the start of the chapter. The steps included were framing your question, understanding your data, choosing a method, processing your data, and looking at the results. These steps are important for ensuring that you are approaching your analysis correctly and choosing the right methods. The chapter also details the different types of geographic features: discrete features, continuous phenomena, and features summarized by area. Discrete features are where the presence of a feature can be determined at a specific pinpointed location. Continuous phenomena blanket the entire map and can be enclosed by boundaries. Features summarized by area get a count or density of features within an area’s boundaries. A lot of data is like this, but does not have precise location details. The differentiation between geographic features is important for determining how to analyze the data. Geographic features can either be vector or raster. For vector features, each feature is a row in a table and feature shapes are defined by x,y locations. Vectors are used for discrete features, data summarized by area, and continuous categories. For raster features, the features are represented by a matrix of cells in continuous space. Rasters are used for continuous categories and continuous numeric values. They can also be used for discrete features when layering. The chapter also discussed how geographic features can have different attributes. These attributes included categories, ranks, counts, and ratios. At the end, the chapter detailed how to work with tables when using GIS. Subsets of data are selected to work with or assign attributes values to. Attribute values are calculated to assign ranks, ratios, or averages. The attribute values can be summarized to get statistics. Overall, I felt that this chapter did a good job covering the basics of understanding geographic data usage in GIS.

Chapter 2:

Chapter 2 introduced some of the information needed to make quality maps. First, you need to decide what to map. Different maps require different types of information and different amounts of information, so you must decide what is right for the map you are trying to make. Considering how you will use the map will help you make this decision. To prepare your data to be mapped you have to make sure that the necessary geographic coordinates and categories are assigned. If the data come from the GIS database, then coordinates are likely to already be assigned. You can map a single type of feature or map by categories. When mapping by categories you can choose to group the categories. If you have more than seven categories, it is recommended that you group them into broader categories. However, grouping categories can change how the data is perceived by the reader, so be careful with how you group them. There are several ways you can group categories in the data. These include using two different codes to represent categories and subcategories, joining a detailed code to a general code after, and assigning symbols to various detailed categories that comprise each general category. When using symbols it is important to do it effectively. Use a single symbol for each individual location, but do not overcrowd the map. For linear symbols, using width and pattern differences are helpful for differentiating the symbols. You should also make the symbols for similar categories shades of the same color. If you are printing the map make the symbols larger and keep in mind that printers usually have better resolution than screen displays. It was also discussed in this chapter that adding reference features, like recognizable landmarks and roads, can help orient the reader. Adding relevant features, like adding store locations if you are mapping customers, can help add context to the map. Map reference features should be displayed in pale colors. When analyzing the patterns on your map, you may need to zoom in or out to see patterns, so keep that in mind when sizing the map. This chapter helped me understand important factors when making maps, especially in regards to using categories and symbols.

Chapter 3:

Chapter 3 discussed more important factors in creating maps, with a focus on quantities, classes, and map styles. It was again discussed how it is important to understand the goal of your map before making it. You need to consider what kind of data you are mapping. Are your data discrete features, continuous phenomena, data summarized by area? Understanding this helps you decide how to display the data. You should also consider if you are using the map to explore patterns or if you are presenting the data. When exploring you should show more detail to find patterns, but when presenting the map use generalized data to reveal patterns. There are several ways that quantities can be used in displaying data in maps. You can use counts, the actual numbers, or amounts, the total of value, to display discrete features or continuous phenomena, but not for summarizing by area. You can use ratios to show the relationship between two categories to even out differences between large and small areas to map more accurately when summarizing by area. Ranks can be used to put features in order from high to low and show relative values instead of measured values, which is  useful when direct measures are difficult. You can use classes to display your data in a way that is easier for viewers to understand. There are several classification schemes that can be used. These include natural breaks, which find patterns inherent in your data, quantiles, which compare areas of roughly same size, equal intervals, which use equal intervals to appeal to a nontechnical audience, and standard deviation, which shows if features are above or below average. Each of these schemes have their own advantages and disadvantages, so it is important to consider carefully which best fits the needs of your data. It is recommended that you only use 4-5 classes in your display. This chapter also discussed important choices needed in making the maps. Different types of data need to be displayed in different ways. Maps of discrete locations and lines should use graduated symbols, charts, or 3D views. Maps or discrete areas or data summarized by area should use graduated colors, charts, or 3D views. Maps of continuous phenomena should use graduated colors, contour lines, or 3D views. There are several things to consider when using these displays, like colors, sizes, intervals, and perspective, so care should be taken to make these decisions. Effectively displaying your data allows for patterns to be found most efficiently. I found this chapter to be helpful in understanding how the seemingly small features of maps can have a big impact on how they are interpreted.

 

Chapter One

Mitchell begins by framing the process of GIS analysis similar to that of the scientific method: First with asking a question, then researching and compiling and presenting data in a digestible format based on the type of data presented. I find this similarity very interesting, yet explainable, as GIS analysis and GIS as a software is based heavily in the environmental sciences, especially geography. Additionally, Mitchell highlights multiple careers that could benefit from or currently use GIS technology, even if they are not associated with the environmental sciences. Careers such as criminology, law (Mitchell highlights how GIS data could be included in court cases), and development all use or could benefit from GIS technology or analysis. In the next section, I learned of discrete features on maps, which include color-coding, shapes, etc. to highlight and present a certain feature of the map, such as streams. Continuous phenomena, another new term to me, are phenomena that can be measured anywhere, such as precipitation. Features summarized by area are used to show density of something in an area, such as population density. All of these are reliant on either of two ways to represent geographic features: Vector models, which rely on the x,y coordinates of a feature to shape out the features. The other, raster models, use cells to shade in and represent a feature, and layer on one another to represent intersecting features. A disadvantage of raster models is that larger cells lead to a loss in detail, so some may choose to make the pixel size of the cell smaller for more detail. Additionally, since map projections are distorted by the curvature of the Earth, mapping larger areas such as states, countries, or continents means that this distortion needs to be taken into account, while with mapping smaller areas, this distortion is negligible.

Chapter Two

When deciding what to map, Mitchell highlights two questions that should be taken into account for GIS analysis. First, what information do you need from the analysis? This will largely differ on a case to case basis, as Mitchell highlights with the examples of police mapping crime rates or a retailer mapping their audience and where they live in order to place the most effective advertisements. Second, how will you use the map? Audience should be heavily considered, especially for factors such as the amount of detail for the map, labels, whether to include reference locations such as streets and landmarks, size of the final planned map, etc. I find these thorough steps in analysis interesting from a professional standpoint, as the process of deciding what to map varies heavily between tasks and audience, in comparison to other forms of measuring data like composition analysis in soil science or raw data in the aforementioned case of crime rates. Additionally, this section highlights both the scientific and communication skills required for GIS analysis, as researching and understanding your audience is incredibly important to conduct a thorough GIS analysis, as Mitchell notes. In the next section of Mitchell’s introduction to GIS and GIS analysis, we learn about preparing data to be used in mapping. I find it interesting that some of the data is hierarchical, and how hierarchies are assumed in the data. Additionally, in the following section, the rule of seven categories to best show data points is very interesting to me, as I originally thought that far more categories would be feasible given that categories are not similar colors. However, thinking back to GIS-made maps that I’ve used for research and for simplifying my thoughts, most maps were not as complex as the zoning map Mitchell uses as an example, and grouped some categories together, even if the audience was scholars and researchers.

Chapter Three

Mitchell starts this chapter reflecting on terms from the first chapter: discrete features, continuous phenomena, or data summarized by area. With additional knowledge from the previous chapters, the context of data types and different forms of quantification are mentioned, allowing the reader to understand these previously learned concepts in context. Following this tie-in to previous chapters, the reader is presented with different ways to present map data in a graduated format; with symbols, shading, etc. in order to analyze patterns in the data in addition to mapping discrete features. This section helped me better understand the content of the chapters in a visual way, highlighting the intersection between discrete features and data analysis in Chapter 2. A new concept in this chapter is types of quantities: counts and amounts, ratios, and ranks. Counts and amounts is the raw data mapped directly, such as the number of restaurants in an area, or the population sightings for a species. Given that the data is placed as points on the map, I assume that counts and amounts quantities only work on smaller amounts of data unless the points of gradation are grouped together in areas of high concentration. Ratios and ranks are less direct forms of quantitative data, ratios being based off of the data in relation to another factor, such as the ratio of schools to children, while ranks put the data into gradual tiers of severity, assigning a shade to each level. Thinking back to maps I have seen both inside and outside of an academic context, I have seen all of these forms of data presentation on maps. Interestingly, I have noticed that in an academic setting, I have seen quantitative data presented more through ratios and ranks, while when presenting data to the general public, counts and amounts are more widely used.

Personal summary/Comments

Chapter 1 – Introducing GIS analysis 

Chapter one explains what GIS analysis is and helps us understand what geographic features/attributes are.  For example, the chapter starts by stating that “GIS analysis is a process for looking at geographic patterns in your data and at relationships between features”.  Which is basically saying that, from the layered maps or the collection of maps used to actually do GIS, it’s just an analysis of that data that helps find some sort of correlation to make the data make sense.  That’s what I got, at least; it then goes into talking about what I assume are the steps for GIS analysis.

Step one – Framing your question: this step covers the fundamentals of what you’re actually asking or what you’re trying to prove/show; in the reading, they used “Where were most of the burglaries last month”?  It also states that you should try to be as specific as possible and approach the question with different methodologies depending on what you’re actually asking and how you think it can be resolved.

Step two – Understand your data: this step tells you that, to understand your data, you need to know what’s missing and how to acquire it; the chapter mentions that sometimes one method of looking at data will only get you so far. Which means sometimes you’ll need to either approach it with a different method or gather new layers to help map out the issue.

Step three – Choose a method: the chapter states that there are almost always 2 -3 methods to obtain information. (However, it doesn’t really give you any methods to help you get an actual idea of said methods. Which is a little disappointing)  It then tells you that the same method won’t always be useful; it’s up to the person whether or not they believe said method is viable.

Step four – Look at results: basically states that you interpret the data to help it make sense

Step five – Look at the results: This step states that the results can come in all sorts of ways. Such as maps, charts, or tables. The reason for this is that some questions are just better explained in different expressions than others.

Chapter 2 – Why Map Where Things Are

Based on the title of this chapter, you can assume it was primarily about mapping and why things are mapped. As for the overall objective of this chapter, it was to explain the importance of mapping things, what exactly your mapping is, and preparing/analyzing your patterns/data. The chapter starts by explaining the importance. “Mapping where things are can show you where you need to take action.” In this instance, they go back to their original question of burglary locations or just overall crimes. They then explain that by mapping out said crimes, they are able to create police routes to monitor the areas with higher crime rates. This tied into “what to map” because in this example they wanted to lower crime rates, so they mapped out all the areas with crime, not just some but all crime. They then created a patrol route.

I assumed this is kinda how cops created their routes (not sure if this is even an actual real-life thing or just an example), but it makes sense that this is how they would do it. (Once again, if this is actually how they make their patrols). I also had no clue that GIS could be used for things like this, well not until last week when I officially found out what GIS is.

In the reading, it also talks about categorizing, such as color-coding specified areas so you know what’s where. However, in the reading, they specifically mentioned 3 options.

Option one – Assign a general code to each record in the database, like RUR (Rural) and RES (Residential)

Option two – Create a linked table to match detailed codes with general codes. This one kinda confused me; it showed a picture with RUR (Rural) and RES (Residential) as general codes and some other letters/ numbers as general codes

Option three – Assign categories on the fly by specific symbols (this is the one where everything is color-coded)

Chapter 3 – Mapping the Most and Least

As the title states, this chapter primarily talks about mapping both the most and the least of your specified target. The reason for this is that it allows you to gauge the relationships between them. If you were to only map the most or high end, everything would look relatively bad or good, depending on the topic. (The same effect on the inverse)

In the reading, it uses mapping both the most and least to effectively track past and ongoing events. One example of this in the chapter they talk about is average annual precipitation. They track both the most and least to help make a gradient of color (dark blue = more rain while light blue = less rain). Now, the reason I chose this one specifically is that this is exactly what you see every day on the news; if you watch a weather channel, they’re going to show the amounts of rainfall, both the most and the least. This helps prove that it’s an effective measure.

Let’s say they focused on the most, and you got rained on because it didn’t make the cut; I know  I’d be annoyed.  So it makes sense that you should include both the most and the least.

 

 

“Into to GIS Analysis”

GIS analysis finds patterns and relationships in spatial data to solve real world problems. The workflow follows a five steps process: find & define your specific question, understand your data, choose a method, process it, evaluate the result & lastly form a conclusion. Some important terms in the chapter:

1. Feature types: Discrete (points, lines, polygons), Continuous (gapless surfaces like elevation), or Area (zip codes, census tracts).
2. Data models: Vector (coordinate based) or Raster (cell based). 
3. Attributes: Categories, Ranks, Counts/Amounts, or Ratios.

GIS work involves but is not limited to; querying, calculating, and summarizing tables. Stuff depends on matching these three components listed above in the correct manner such as relating the right data model with the right attribute both according to your question. Hence, before I start any analysis I will understand my question foremost and then move onto deciding things because that lone thing can make it or break it. 

“Mapping Where Things Are”

Mapping locations shows distribution, clustering, and dispersion. Data need be prepped first with accurate coordinates and clean category codes. Like the question was the most important thing in the first chapter, your data means just as much here. Three key things again: 

1. You can map one feature type, isolate a subset, or map multiple categories to show relationships and hierarchy.
2. People can only reliably tell apart about seven colors or patterns so anything past that needs grouping.
3. Symbology rules:
   • Color beats shape for points
   • Vary line width for networks
   • Keep reference layers muted (light-gray basemaps) so context doesn’t fight the data

When we start to build a map most of us just wish to add more and more things, add in more features, add in more information, yes I concede more information might be better but most of the time it is simplicity and visual hierarchy instead which decide whether a map actually works or not and that seven category limit is the hard ceiling. For anything public facing I’ll group categories aggressively and stick to minimal basemaps so the real data stands out.

“Mapping the Most and Least”

Mapping quantities compares places to show trends and concentrations. The big rule: when areas are unequal in size, use ratios (averages, proportions, densities), never raw counts, or the pattern is misleading.

1. Classifications:
   • Natural Breaks: clustered data
   • Quantile: equal features per class
   • Equal Interval: identical value ranges
   • Standard Deviation: distance from the mean
2. Outliers be handled or they compress everything else into one class.
3. Display options: graduated symbols, graduated colors, pie/bar charts, contours.

The classification we pick completely changes the story the map tells, and raw counts should never go on variable-sized polygons. 

Chapter 1:

The chapter starts by explaining that GIS analysis is a process for looking at geographic patterns in data and relationships between features. The data may either be simple or complex. The process for performing an analysis includes five steps. The first step is to frame a question. To analyze something, you need to know the information that you want to find, and this requires forming a question. The second step is to understand the data to be able to determine what method to use. Third is choosing the method. Some methods are less time consuming than others, but only provide a basic understanding, and the methods that take longer produce more in-depth results. The fourth step in processing data and performing the steps in GIS. Finally, the results will be produced as a map, chart, or something similar. 

Understanding geographic features is an important part of GIS. There are three different types of features that can be used. Discrete features are used for discrete locations and lines, and location is able to be pinpointed. Continuous phenomena are precipitation or temperature and can be found or measured anywhere. It blankets the entire area of mapping. Features summarized by area represent density of features within boundaries.

There are two ways to represent geographic features. The first is a vector model, which includes features (discrete locations, events, lines, and areas). The second model is a raster, which is a matrix of cells. It is important to have the same map projection and coordinate systems to ensure accurate results. 

It is important to understand geographic attributes to determine the type of analysis you want to do. There are five attributes. Categories are represented by numeric codes or text. Ranks are used for when direct measures are difficult. Ranks are relative, so it is not exact. Counts and amounts show total numbers. Ratios show the relationship between two categories. Categories and ranks are continuous, counts, amounts, and ratios are not.

Working with data tables is important for GIS analysis. Three common operations are selecting, calculating, and summarizing.

Chapter 2: 

This chapter starts with explaining that mapping where things are can show where action is needed. This can eventually show causes for certain patterns, such as a concentrated area for crime rate. 

In order to decide what to map, you need to know the information that you are trying to gain from the map, and how the map will be used. The information needed for a map can differ depending on the end goal. Some maps are used to determine a concentration of something, others can be used for discreet locations. Determining how the map will be used can be determined by the audience and issue being addressed. 

Preparing the data requires assigning geographic coordinates and assigning category values. 

To actually make the map, you put the information into GIS. the features can either be displayed in a layer as a single type or categories. In a single type, only one symbol is used. This can show patterns. Mapping by category uses multiple symbols and can provide a more detailed understanding. This allows for displaying features by type, how many categories there are, which features are mapped, the map scale, how categories are grouped, and which symbols are used. It also allows for reference features such as major roads/highways and landmarks. 

If the map produced presents the information clearly, patterns in the data can be seen. If it is a single category, features can be clustered, uniform, or randomly distributed. Patterns can begin to provide explanations for why things are where they are. While this can provide a visual example, to determine if the patterns are significant, statistics are required to quantify the relationships between features.

 

Chapter 3:

In GIS, people map the most and least to see the relationship between places. Mapping features based on quantities can provide extra information in concentration. For this mapping. You need to map the patterns of features with similar values. 

Knowing the types of features that you are mapping is important to know how to present the quantities to see patterns on the map. This can include discrete features, continuous phenomena, or data summarized by area. 

When making a map, the purpose of the map is important to know how to present the information. To map the most and least, understanding quantities is important to be able to assign features.

Once the quantities are determined, they can be represented by assigning each value its own symbol, or grouping the values into classes. Mapping quantities requires a balance between accuracy and being able to be able to see patterns on a map by generalization of values. Counts, amounts, and ratios are grouped into classes. 

Mapping individual values presents an accurate picture of the data, but may make it harder to read the map. Classes can make the map much easier to read. For making classes, they can be created manually or by using a standard classification scheme. Classification schemes include: natural breaks, quantile, equal interval, and standard deviation. It is important to be able to choose the best one for the information you have. 

Once the data has been effectively classified, the next step is making the map. Make sure that only important data is used to ensure easy comprehension by readers. GIS provides these options for creating maps to show quantities: graduated symbols, graduated colors, charts, contours, and 3D perspective views. 

• Graduated symbols: map discrete locations, lines, or areas
• Graduated colors: map discrete areas, data summarized by are, continuous phenomena
• Charts: data summarized by area, discrete locations, or areas
• Contour lines: show rate of change in values across area for spatially continuous phenomena
• 3D perspective views: continuous phenomena to help visualize surface

Chapter 1

The first chapter introduces us to many of the essential techniques used in mapping and display of geographic features. Beginning with the first section you realize that it is paramount that you be specific in defining the geographic features you want to display and their corresponding attributes. Next we examine the choices one must make when deciding the way you want to gather/ display the information in question. In terms of display we are presented with the ideas of vector or rather format that have different levels of scalability with the vector option being adapted to a wide range of scales the rather methods looses sharpness at smaller scales but is perhaps more adept at showing the blend between to regions. We also have ways of defining the data we aim to present/analyze. Very distinctly data can be modeled discretely while regions with similar conditions or qualities are modeled continuously. Lastly they can be summarized by areas where specific points are given greater importance by being defined to a distinct geographic location.

 

I find some confusion about how lines might be drawn with individual points. What sort of software might be used to generate points on a line or are the points created by hand to model larger phenomena?

 

What advantages might the Rather method have at a smaller scale. Would it be easier to demonstrate the pervading category within a cell using the rather model as opposed to showing the distinctive line used by the vector model?

 

Each feature displayed on the map is given different attributes which are not shown on the map but rather in the table of information but ultimately determine how each feature is represented. Geographic borders remain constant between different features.

 

Chapter 2

The text states “ The GIS reads these and assigns geographic coordinates.” This got me thinking. Are all GIS the same or do some have different capabilities and handicaps?

 

This chapter of the textbook seems to be more focused on what the GIS is capable of and is less focused on the specific geographic features and their attached attributes that the user implements into the GIS. It also dived into the aesthetics of mapmaking and gave some helpful tips on styling, shaping and color coding of various features as well as how you can make maps more simplified through multiple levels of map complexity. One essential point that I got from this part of the textbook is that your map should aspire to be readable by everyone but should also be helpful to experts in whatever subject they aim to map.

 

There was also some focus on what to display to convey information best to the reader. I am wondering if there will be a greater emphasis on what to include and not include in your map in one of the coming sections ex: what things not to input into your map to make it seem unprofessional(clip art, 3d graphics etc).

 

I thought it was interesting that the maximum number of colors you should include was 7. I hadn’t thought about mapmaking that way psychologically but it does make sense. Is there some fluctuation in this where people can comprehend more than 7 shades? It is also sometimes necessary to use more than 7 shades. How can you make this more user friendly?

 

Chapter 3

The idea of summarizing data from most to least seems somewhat elementary to me. Would it not be better to explain how these things are programmed into a map?

 

I think the distinction between count and amount is an important distinction to make but I feel like the words are so similar would other more technical terminology make definitions seem more distinct example #categories paired with amount, etc..

 

The 3D modelling looks complex and I had not thought about the use of a light source to create shadows and how the positioning of that light source might create a very different visual.

 

This chapter focused on display of variables and mapping things from most to least. It examined the different ways you can choose to group numbers or ways that you can have the GIS automatically separate numbers into different classes using things like natural breaks. It then talked about some more ways to distinguish between these different classes you have made, For example: using line width when showing quality of stream health etc. and introduced charts to show categorical data internal to the area on the GIS. The chapter also gave a very helpful breakdown of the advantages and disadvantages of different types of display styles which I thought was really nice and simplified the earlier knowledge well and provided basis for comparison.

Chapter 1:

GIS is collecting data and analyzing the patterns that the data presents. The steps in mapping an analysis is to start by asking a specific question, understanding all aspects of the question, choosing a scientific method, then processing and looking at the data to make sure it valid for presentation. There are also three geographic features which include features that are discrete, a continuous phenomenon, or summarized by area. Discrete features include the location to be pinpointed, meaning it’s either present or it’s not. Continuous phenomenon is mapping data such as precipitation or temperature since they can be measured anywhere and  uses a process known as interpolation to plot the given values. Continuous phenomenon can also plot data that is the same throughout a given area, such as soil composition or vegetation. Lastly, features summarized by area count the amount of features within the plotted boundaries. This process typically maps diversity in populations. Other key words from the chapter include vector and raster. The vector model showcases data in a line other than table and are defined by x,y,x locations on the map. The raster model shows features in a continues space with layers of specific cells. A key idea from the chapter was to understand the geographic attributes of defining the feature used and then describing it. The types of attribute values are categories: smaller groups, ranks: features in order from high to low, counts and amounts: show total numbers, ratios: show relationship between two quantities. The last concept from this chapter was how to work with data tables by selecting the rows of data in a logical expression then calculate. This section confused me a bit because I wasn’t sure on what this section meant. But lastly the chapter expresses to summarize the values into statistics.

Chapter 2:

The chapter opens why stating the importance of mapping information. I thought the examples given such as crime mapping and mapping environmental changes were important because it gives people a gauge on why things are happening. Altering mapping these disturbances, the question and be asked to why this is happening in this area and analyzing if these same features are   present in similar places. After the data is collected, it’s up to the person who collected the data on how it is to be presented. Some ideas to make it better for the viewer was to add information that was collected or the lack there of, while also adding important land marks such as post offices, parks, or street names. This important can be valuable for people if the area is unfamiliar. Some key ideas when mapping data was having geographical coordinates like longitude and latitude. There is also the importance of categorizing the information. The example I thought was interesting was “crime” but them identifying the crime was assault, burglary, or other types of crime. One key idea from this chapter was how to map GIS by using a pair of coordinates for a location with the name of the address or a symbol to identify the specific target location. Other notable features include drawling lines for roads and filling in colored spaces for open land. I this idea was important for the chapter. The chapter goes into the importance of grouping and organizing data for the reader. A key claim from the chapter was to not extend more than 7 categories because the information can become blurry. However, it’s important to note all data but grouping what is similar and important is a skill that is used in GIS. Some mapping features included thicker lines for high traffic roads and different symbols with unique colors will also distinguish between features on the map. I thought this chapter gave important information of the stylist choices when mapping.

Chapter 3:

Mapping the least and most amount of data can be important for people to see relationships between places or know which area fits their needs. Discrete features are typically one location represented with larger symbols to represent the density. A continuous phenomenon can be displayed with difference of shading between densities. A question I had from this section was about the difference between graduated colors and shading. This chapter breaks up these two phases, however from the maps, they both look like lighter colors to darker colors showing the change in densities. I did find it interesting how the mapping of population in an area can be beneficial through looking at densities of population and mapping human activity, while also mapping environmental changes and data. A key phrase that I learned from the chapter was counts and amounts. This phrase is identified as the counts being the actual numbers of features on a map where the amount is the value for each feature. Ratios was also an important key word from the chapter and this was defined as the relation between two values and this can be showcased through averages, densities, and proportions. Finding the average is just dividing the total number by the number of groups. With categories, I was a little confused on how to calculate it. With densities, they show how concentrated values are and these are calculate by dividing the value by area of land. Further in the chapter, other important aspects of mapping included creating classes or mapping individual values. In classes, there are quantile, equal interval, and standard deviation. Lastly, towards the end of the chapter, we are shown difference types of mapping with their advantages and disadvantages of each system of mapping.

Chapter 1

     Spatial Data has grown tremendously outside of the scientific world, becoming available to many other sources. GIS answers questions about why things are done the way they are and how they are related. There are two ways to evaluate spatial data, depending on the question being asked and how the information will be used. The first method contains the bigger-picture kind of information and is quicker to access, and the other kinds of methods require more digging and time to process the more specific information. The information found is typically present in many different ways, like tables, maps, etc. Depending on how information is presented, the data is either valid or useful, or it will say that more digging is needed.​

      To use GIS effectively, users should understand the types of geographic features represented in the software. Features on a map can be described as discrete, continuous, or summarized phenomena. Discrete features, such as specific locations, are depicted as lines or dots depending on the settings. Continuous phenomena, like weather patterns such as precipitation and temperature, are measured through equally spaced data points with no visible gaps. GIS software applies a process called interpolation to assign values to areas between these points. Continuous data can also be represented by enclosed boundaries (such as those showing soil or vegetation types), which are used to illustrate large, uniform areas of the landscape. However, these boundaries are not as definitive as discrete features. Features summarized by area primarily indicate the density within a specific boundary—for example, the number of businesses in a zip code or the number of houses within a certain radius.

      Geographic features are shown through two different models, vector and raster. In a vector model, features are displayed in a table and buildings are represented as x,y locations connected with dashed lines. Raster models are presented as a matrix of cells by layer. Each layer is a specific attribute. Cell size is vital to an accurate map because if the size isn’t perfect, then information is lost. 

     There are five different types of attribute levels. These are types of attributes that determine how each feature is analyzed determines what level to use.

Different levels of attributes:

1. 1.  Categories – Groups of different features that are alike in some way and are represented in code or numbers.
   2.  Ranks – Features are put in order from highest to lowest and used when features are hard to distinguish
   3.  Counts – The count is the actual number of features on a map
   4.   Amounts –  The quantity connected to a feature
   5.  Ratios – Comparing two quantities by dividing one by the other

 

Chapter 2

 

     Chapter 2 focuses primarily on how and why features are placed where they are placed. Viewing a map now is much clearer to me because chapter helps me understand how to find patterns throughout a map. The map features are always determined based on how the information is presented and how the map is used. For instance, the police department tracks where crimes are committed and what types using GIS to better monitor high crime areas each month.  Prior to placing features on a map, all features included will have geographic coordinates as longitude and latitude values and be identified as a type (must fall into a category). Mapping can occur as a single type because GIS will use the same kind of symbol and suggest that this map can be explored further. As features are added, GIS will use the applied coordinates to create lines or areas to define shapes for specific areas or smaller / single features will be drawn as a symbol defined by coordinates. Instead of laying all of the features in one layer, smaller patterns can be revealed by creating a subset which can only be represented in an underlying layer instead of just one big layer.

     When one map has a multitude of categories, it is suggested that groups are created to sort the categories into smaller sets of data.

Option 1: Assign each record 2 database codes. One for detailed category and the second for  its general category

Option 2: Create a table containing one record for each category corresponding to its general code. Once the map is ready to be displayed, the table and map will be linked together showing general codes with the features. 

Option 3: Assigning categories by specifying the correlated symbol to go with it. Mostly used for single locations

Chapter 3

     Mapping areas with the highest and lowest concentrations of specific variables is invaluable for businesses in strategic planning and market analysis. For instance, when a physician’s office considers expansion, mapping the ratio of people per existing office per mile can highlight underserved regions. This helps ensure a new location addresses real gaps in access, which increases the likelihood of success and optimizes resource allocation.   

     Understanding the three types of map features—discrete, continuous, and summarized—enhances how landscapes and demographic data are visualized. Discrete features pinpoint specific locations or boundaries, continuous features represent gradients like population density, and summarized features aggregate information over defined areas.

     Standard classification schemes are essential tools in GIS for grouping similar data points, revealing underlying patterns, and making complex data more interpretable. These schemes rely on how the data are distributed. When data points are evenly distributed, classifications such as equal intervals or quantiles can be used for clear, balanced mapping. Charts and histograms help visualize this distribution. If the data have natural groupings or outliers, methods like natural breaks (Jenks optimization) are preferable, as they better reflect the true structure of the data.

     Using GIS becomes more straightforward when data is evenly distributed, as outliers and skewed distributions can complicate analysis and visualization. Careful selection of classification methods ensures more accurate, meaningful maps that support better business decisions.

     There are five ways to show quantities using GIS software: 

1. 1. Graduated symbols – includes locations, lines and areas and is best used for minimal featured maps
   2. Graduated colors – includes areas and continuous phenomena and makes patterns easy to read
   3. Charts – Used for specific locations within an area to show categories and quantities
   4. Contours – Used to represent rate of change across large parts of area
   5. D perspective views – Adds visual impacts throughout the map

Chapter 1

 

Maps come in many forms, think of paper maps that show minimal information such as roads and towns.  GIS maps have spatial pictures and can be created to show in depth information.  Chapter 1 is about advance mapping where you can find patterns, trends and work towards solving problems. 

Some key terms I found interesting listed below.

 

Map Features: GIS uses three main shapes to draw everything.  Points, which are tiny dots for certain locations.  Lines, connected paths such as pathways and roads.  Polygons, shapes with boundaries that outline an area such as a county.

 

Discrete Data, has clear edges like property lines.

 

Continuous Data, flows across space with out hard borders such as temperature

 

It is amazing that almost everything can be mapped.  How can you protect private information from becoming part of this system?  I wonder if people can use this tool to commit crimes?

 

Chapter 2

 

This chapter involves plotting locations  and spotting groups clustered together.

Mapping where things are located.

 

Single Symbol Mapping, giving every single item the same icon and color

 

Clusters, tight bunches of dots

 

Outliers, lone dots far away from everything else

 

If you are going to map everything your map could look messy. Map scale has to be right so that your information can be interpreted.  Are there sources to help pick the best map scale?

 

Chapter 3

 

Talks about mapping numbers and the importance of calculating them correctly before putting them on your map.  You do not want incorrect information available to interested parties.

 

Data grouping,  how you split up numbers into groups before picking colors

 

Normalization, fixing raw counts so a fair comparison can be made.

 

Choropleth Map, classic shaded map where areas are colored lighter or darker based on their numbers

 

So you should never map raw totals for large regions. You need to make sure detail is incorporated or your map will just show basic information.

 

How do you choose color shades?

Mitchell, chp. 1,

Andy Mitchell describes GIS as “a process for looking at geographic patterns in your data and at relationships between features.” (Andy Mitchell, 2020, pg 3). This description of GIS narrows down the broad field of GIS mapping into an understandable description of how GIS analysts collect data and record patterns to create a multilayered model of recorded data. As described in the textbook, collecting this data is similar to the typical scientific method. This process consists of asking a question, understanding your data, choosing a method, processing the data, and analyzing results of the process. In GIS, there are continuous phenomena, which are continuous data that starts as sample points. GIS analysts then assign values to the area between these sample points. This process is known as interpolation. This process is crucial for collecting precise measurements and recording data of an area over time. It is crucial to note that you can also treat some noncontinuous data as continuous to create maps that highlight how quantities may vary across a given location. This process helps fill data gaps from unmeasured areas and simplifies complex, intricate data. 

Additionally, GIS utilizes map projections and coordinate systems to ensure accurate results when combining data layers. “A map projection translates locations on the globe (which is almost a sphere) onto the flat surface of your map. All map projections distort the shapes of the features being displayed, as well as measurements of area, distance, and direction.” (Andy Mitchell, 2020, pg 13). The quotation explains that a 3D sphere is translated onto a 2D map, and this process distorts the features to compensate for the dimensional change. This is one of the main complexities in GIS and topography: changing the 3-dimensional measurements into a tangible 2-dimensional mapping system.

 

Mitchell, Chp. 2,

The second chapter varies from the first by describing the processes of mapping, where things are in relation to their location on maps. You must first ask what information you need and how you will use the map. After concluding the intent and required data, you must prepare your data, such as coordinates and assigned category values. The category values portion of the data is crucial to assign features to a correlated code in order to categorize them. I found this portion of the reading fascinating due to how you categorize the data by hierarchical types and subtypes in order to create organization within the masses of data to maximize simplicity and efficiency. After you have prepared and organized the data, you can begin actually creating your map. You can map all single features or subset features in order to create more intricate data that reveals patterns that are not always apparent with just single features. The GIS system’s role in this process is to store the location of each feature as a set of coordinates or pairs. Various unique symbols are used to pinpoint the locations of the features that you input. The textbook expresses that you typically want to include 7 or less categories because more than this can create difficulty in seeing the patterns. You can have more than 7 categories in your map however, you want to group the categories into each other to make them easier to identify. In order for your map to be meaningful, you want to utilize recognizable features such as landmarks like highways, towns, rivers, etc. You can also use reference features specific to your map and analysis to observe the relationships in the data. An example of reference features could be if you’re mapping the growth of a fast-food chain, you could map the nearby competitors that contribute to fluctuations in data and have geographic relationships.

 

Mitchell, Chp. 3,

The third chapter expresses the importance of grouping the map data based on quantities and mapping the most and least. Mitchell, Chp. 3 explains this by saying, “Mapping features based on quantities adds an additional level of information beyond simply mapping the locations of features. For example, mapping the locations of businesses gives a sense of where workers are, information that might be useful for a transportation planner. But mapping the businesses based on the number of employees at each business gives a much better picture of where employees are.” (Andy Mitchell, 2020, pg 52). After reading this chapter, this description and example helped me understand the different utilizations of mapping locations and features like I described previously, and mapping quantities in order to add additional information and create a more organized map. The example that Mitchell used highlights how the locations of employees can be extremely useful for certain data, but the quantifiable number of employees at each individual location paints a much better picture of where each employee is across the different locations. The quantities that you are mapping (most and least) can be categorized in counts and amounts, ranks, and ratios. Counts and amounts display the total value of each feature and its extent in comparison to other features being recorded. It is important to note that counts are used for the actual number of features, whereas amounts are used for describing the total value associated with the features. Ratios, however, show the relationship between various quantities that are collected by dividing one by the other to collect ratios like proportions and averages. Rank ‌these features in order in terms of highest to lowest of the recorded data. An example of a rank: maybe if you’re collecting data on thriving tree species in an area, you would rank the strongest trees at the top of the rank and the weakest at the bottom. These 3 forms of data organization help to sort‌ large quantities of data into understandable and observable sections.

Sources:

• “Andy Mitchell’s, May 26, 2020, Esri Guide to GIS Analysis, Volume 1, Second Edition (Chp.1, pg.3), (Chp.1, pg. 13), (Chp.3, pg. 52)