GIS Chapter 2

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Author:
dtarasov
ID:
99964
Filename:
GIS Chapter 2
Updated:
2011-09-05 21:26:18
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GIS second chapter
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Description:
Terms and concepts from the second chapter of Mastering ArcGIS by Maribeth Price.
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  1. What kinds of data are there to consider when creating maps?
    • Nominal
    • Categorical
    • Numeric
  2. What are nominal data?
    Data that identify or name objects, such as the name of a state.
  3. What are categorical data?
    Data that separate features into distinct groups or classes. Represented by unique values maps.
  4. What are ordinal data?
    Data that are grouped by rank based on some quantitative measure, although the measure is not necessarily linear in scale. Example: classifying cities as small, medium, or large.
  5. How should ordinal data be represented?
    If the values are text, use unique values maps, but the colors should be the same shade and give a sense of increase. If the ordinal data are numeric, either unique values maps or graduated color (choropleth) maps can be used.
  6. What are ratio data?
    Numeric data with a meaningful zero point such that zero indicates the absence of the thing being measured. Example: precipitation.
  7. What are interval data?
    Data that have a regular scale but are not related to a meaningful zero point. Example: temperature (when measured in the Celsius or Fahrenheit scale). Any measuring scale that can have negative values must be an interval scale.
  8. What is another term for choropleth maps?
    Graduated color maps.
  9. What are thematic rasters?
    Rasters that represent map features or quantities, such as roads, geology, elevation, or vegetation density.
  10. What are discrete rasters?
    Rasters that are used to store objects; contain groups of adjacent cells with the same value.
  11. What are continuous rasters?
    Rasters that store values that represent a continuously varying quantity such as elevation.
  12. What is the classified display method?
    A method of displaying rasters; divides the values into a small number of bins, and a color ramp is chosen to assign colors to each bin.
  13. What is the stretched display method?
    A method of displaying rasters. Subjects the raster to a slice, which rescales the values into 256 bins, and then matches each bin to one of the 256 shades in a color ramp. A slice can be thought of as a classification that creates 256 classes.
  14. When to use the Jenks method of classifying numeric data?
    The method works well on unevenly distributed data--in other words, almost any data set.
  15. When to use equal-interval classification?
    When dealing with ratio data, such as income or precipitation.
  16. When to use defined-interval classification?
    When comparing classes composed of percentages, dollars, temperatures, and other values where specific break values are desired (100, 200, etc.) because it creates rounded values in classes that are easy to interpret.
  17. When to use quantile classification?
    When dealing with linearly-distributed data.
  18. What is geometric interval classification?
    Bases the class intervals on a geometric series in which each class is multiplied by a constant coefficient to produce the next-higher class. Works well with continuous data such as precipitation.
  19. When to use standard-deviation classification?
    When it is needed to highlight which values are typical and which are outliers. Best applied to normally-distributed data.

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