Using Exploring GIS

Chapter 1

1. Open your wallet or purse. Examine all the documents, cards and other items. How many forms of measurement are contained? What scales of measurement are used? How are these measurements represented? How many involve some form of geographic information?
2. Read through the explanation of the categories of a land use inventory, a soil survey or a vegetation inventory (or any exhaustive coverage system). How distinct are the categories? How many criteria are considered? Do member of the class share specific characteristics? Is there some form of intermediate membership in the form of probability or proximity to some 'prototype'?
3. In some compilation of geographic attributes (such as the Statistical Abstract of the United States), study the units of measurement for a number of tables. How many of these fit into Stevens' ratio 'level'? Are they 'extensive' or 'derived'? Are the units arbitrary or are any of a higher scale (such as absolute)? How are these units described as a reference system?
4. Investigate the different spatial reference systems (coordinates, datums, etc.) in use for some chosen region. Describe the techniques used to convert from one system to another.
5. How do the various calendar systems (for example, the Chinese lunar calendar, the Muslim and Jewish calendars, the Mayan system) adjust the lengths of years to fit the astronomical realities? When is the next 'leap second' and why?

Chapter 2

1. Visit a map library. How many different measurement frameworks can you find? Take a regular topographic map, and figure out how many distinct measurement frameworks are portrayed. What compromises are required to include them on a single sheet?
2. Legal restrictions on the floodplain are usually contained by a line delimiting the 100 year flood (the flood with an average estimated recurrence interval of 100 years). Why set the risk level at this figure? What level of risk is implied in the protection against other risks (aircraft accidents, automobile accidents, cancer, radiation etc.)? Are people consistent about risk?

Chapter 3

1. Take a reference (topographic?) map of your neighborhood or home town. Place a series of successively coarser grid cells over the map and consider how to measure various themes at each level of resolution. What measurements would make sense?
2. Obtain a few maps at different scales. Estimate the width of lines used to represent roads, political boundaries, streams and other features. Calculate the ground distance covered by the line symbol. How does this distance compare with the actual width of the feature in question. What effects might the line symbol have on the accuracy of the data?
3. Digitizing would be the appropriate penalty for what crimes?
4. From a web browser on the Internet (or its successor), 'surf' the network looking for various forms of geographic information. Use the textbook web page as a starting point. How many themes can you find that cover your region of interest? Who has established these servers and where are they? Can you download data directly or must you order (and pay for it) first? In what format is the data stored? [see Data Hunt in Case Studies]
5. Find two adjacent topographic sheets compiled or revised at different dates. Examine the edges to see if all the lines match and all the objects have consistent attributes. If they all match, what does this mean? If there are differences, how might they have occurred?

Chapter 4

1. Starting with a land cover map and a topographic map of roughly comparable resolution (scale), extract the water bodies from the land cover map using isolation. Compare with the object view of the water bodies on the topographic map. What parts are essentially identical? What differences emerge? Explain how the measurement framework of each source contributes to the differences.
2. Examine the census tabulations for a city you know. Take two ratios for census tracts, like % minority and % over 65. See if the areas with relatively high rates on both measures are due to a concentration of older minority population, or a coincidence of non-minority older persons in areas with high minority concentration. The crosstabulation tables in the census may help tell the difference.
3. Read the soil report for a county in your region, with particular attention to the description of inclusions. For some variable of interest, like permeability or crop yield, determine if the inclusions tend to be similar to the primary soil mapped, or quite different.

Chapter 5

1. Starting with two categorical coverages, perform a basic screening overlay analysis using as many different command sequences as you can in the package available. What are the differences in the results? Which method was most direct for AND (two characteristics required simultaneously) and which was most direct for OR (a single characteristic serves to include/exclude)?
2. Obtain a vector version of two categorical coverages, generate an overlay with different values of the 'fuzzy tolerance'. [There should be some facility to filter out slivers.] Describe the differences in the results (geometrically and in terms of total area).
3. With the two coverages used for #2, convert to raster using different pixel sizes. Describe the differences in terms of total area by category.
4. Examine the logical consistency of two independently derived categorical coverages by an overlay. Display and tabulate the area in combinations of categories that seem suspect. Examine the occurrences of these mismatches; are they due to geometric differences (misregistration, positional error, fuzzy boundaries) or are they due to misclassification? Can you tell which is more likely to be correct?
5. The definition of an extensive measurement scale requires a midpoint property: two objects with the midpoint value have the same value as two objects with different values. (For example, two $5 bills equal one $10 bill and no money (zero)). Examine some composite suitability scales to determine if the midpoint theorem really applies.
6. Seek out the site selection process for some project like the Low-Level Radioactive Waste Disposal Facility in your region. What factors are included in the process? Is there a distinction between exclusion and evaluation? How are different components of the environment combined?

Chapter 6

1. Obtain the zoning (or similar building regulations) pertaining to your neighborhood. What distance measurements apply to your residence? Look at the regulations regarding a cement plant, a bar, or something considered potentially offensive, what distances are imposed on these uses?
2. Aldo Leopold recognized the role of edges as habitat as long ago as 1933. See how many of the species in your environment locate nests or feeding sites along edges between various cover types.
3. In 1947, Howard Zipf expounded the 'Principle of Least Effort' for human interaction. Take the convenience stores (or some fairly ubiquitous enterprise) in your neighborhood. Draw the Voronoi polygons around these points. Survey a sample of residents to see which store they patronize if they are faced with a need for 'convenience products' like the classic quart of milk. Is Zipf's principle a close approximation? What factors seem to disrupt the logic of least effort?

Chapter 7

1. Walk across some open land ­p; ideally in a rainstorm ­p; looking at the slope gradient and aspect. Think of the drainage of the slopes. Can you see ridges lines and courselines? Can you trace watershed boundaries in your neighborhood or on topographic maps?
2. Look at the diversity of your surroundings. At the micro-scale, how many different materials cover the land surface in the vicinity of your house (concrete, asphalt, plant species)? How many different land uses are in your neighborhood (you define its limits)? How diverse are the ecosystems in the 100 km around you? How does 'scale' influence your measurement of diversity?
3. Locate all the networks serving you house, apartment or dormitory. How do they arrive on the premises (airwaves, dedicated wires, common carriers, incoming and outgoing pipes, etc.)? How well are the locations of these services known? (Try the Call-Before-You-Dig service ­p; listed as a toll-free number in my directory under Utilities Underground, with a reasonable alibi, to see how you would find out.)

Chapter 8

1. Write out a diary of one day in your life from the perspective of networks. What materials and services do you use? How do you move around during the day? How are these networks regulated? How carefully do you consider the least-cost, least-time path on these various networks?
2. Perform a viewshed calculation for some area near you. Go out in the field and verify its results. What parameters did you get wrong? What measurements would you need to make to improve the model?
3. Take the congressional district for your state, the state legislative districts, the emergency response districts (ambulance or fire), the garbage collection route or some other allocation system. Find out the criteria that should be applied to these districts, and see how well your district fits the official criteria. What other unofficial criteria might have been used to create the specific configuration?

Chapter 9

1. Take a report of some project with a GIS component. Catalog the transformations used to produce the final product. Did the authors recognize all these steps and justify the choices of assumptions and methods?
2. Find out how the taxes are assessed for your neighborhood. There is likely to be a combination of fieldwork and computer models. Look at the assumptions in the computer models, do they results for your property match recent sales of similar properties? Is this property over or underassessed? Will you tell the assessor in only one of these cases?
3. Most ecological studies are carried out on a study area of a meter squared or less. How can one connect the information gathered at detailed scales to a global model?

Chapter 10

1. Obtain the original plan for GIS implementation at some agency, and assemble the actual history of that project. How realistic were the original expectations? Did the expected benefits arise? Is the original budget close to the final total?
2. Compare some different sources of geographic information of the same theme (such as TIGER and the commercial versions of street networks in the USA [such as ETAK or Delorme). How are the differences presented? What tests could be designed to determine the differences? What price differentials go along with the differences in data quality?

Chapter 11

1. Study the adoption process for GIS technology in some institution (for example, inside a city government). What group took the lead? How did other groups get involved? Is administration centralized or is it operated independently in different parts of the organization? What was the training and disciplinary background of the original leaders and the current staff? How was this process influenced by external models or events?
2. Does better information necessarily lead to better decisions? How can you justify expenses on a GIS in competition with expenditures that have a direct impact on social goals? Draw up a list of 'benefits' that can be expect from operating a GIS in a particular situation. How does these benefits compare to general goals?