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# Color schemes

### Computer Cartography

Question | Answer |
---|---|

What are color schemes for? | Choropleth maps |

Who developed most of the color schemes that we use? | Cynthia Brewer |

What do color schemes depend on? | Data you are mapping (qualitative or quantitative) |

Why doesn't Brewer use saturation? | Because people don't understand it |

What is qualitative data? | What you find at a particular location; categories |

What is quantitative data? | Everything else |

What schemes are used for qualitative data? | Qualitative scheme and binary |

What schemes are used for quantitative data? | Sequential, Spectral, Diverging, two-variable balanced, three-variable balance |

How are classes divided in the qualitative scheme? | Hue changes (value is equal) |

How are classes divided in the binary scheme? | Two values (one hue) |

How are classes divided in a sequential scheme with no hue? | Lightness steps of neutral grays |

How are classes divided in a sequential scheme with one hue? | Lightness steps of a single hue |

How are classes divided in a sequential scheme with hue transition? | Transition slowly from one hue to another |

How are classes divided in a sequential scheme with hue steps? | Lightness steps with hue steps that progress through all spectral hues |

How are classes divided in a spectral scheme? | By hue and lightness steps |

Why is the spectral scheme inappropriate for a diverging scheme? | Large hue steps interfere with groupings above and below the midpoint of a diverging scheme |

Why is the spectral scheme inappropriate for a sequential scheme? | Lightness not sequential |

What is the three things is the diverging scheme for? | For data with positive and negative values, for increases and decreases, for positive values comparing above threshold and below threshold (number of families above poverty level, number of families below poverty level) |

Describe a diverging scheme. | Neutral in middle and increasingly darker at extremes |

What does the legend for bivariate maps look like? | a matrix |

How many classes should two variable maps have? | 2 to 3 |

Can GIS programs create bivariate maps? | No. |

How should you pick the colors for a bivariate scheme? | Using Brewer's site |

Describe a qualitative/binary scheme. | Different hues for qualitative variables crossed with two different values for binary variable |

Describe a qualitative/sequential scheme. | Different hues for the qualitative variable crossed with different values for the sequential variable. |

Describe the sequential/sequential scheme. | Cross of values of two complementary hues with mixtures producing a neutral diagonal. |

Describe a two variable balance scheme. | Transition between two hues with similar value throughout the scheme. |

Describe a three variable balance scheme. | Mixtures of values of three hues. |

Describe a diverging/binary scheme. | Two hues with values diverging from the midpoint of the quantitative variable crossed with two values for the binary variable |

Describe a diverging/sequential scheme. | Two hues with values for the diverging variable crossed with greater value steps for the sequential variable |

Describe a diverging/diverging scheme. | Different hue at each corner with hue transitions for lighter midpoints is logical cross for two divergent schemes. |

What is generalization? | When you make the transition from a large scale to small scale map, the large scale map symbols need to be generalized |

What should the first step of generalization always be? | Selection |

Is there generalization software available? | Yes. |

Can everything be generalized? | No, art can't be automated. |

What generalization procedure can be applied to objects that have an area and linear symbols? | Simplification |

What should you do if you have an area with two linear symbols that run parallel to each other? | Exaggerate space between lines and increase width of lines. |

If you have several linear features, and you have to displace one, which one should you displace first? | Manmade features. |

If you have three buildings, what should you do to generalize them? | Aggregate them into one building block. |

Since you have less space at a smaller scale, what generalization feature must you perform to select the features that you will keep and others that you will remove? | Selection |

If you have two types of forests, but only can show one on your map with a smaller scale, what generalization procedure should you perform? | Reclassification |

Who came up with the principles of selection? | Toepfer and Pillewizer |

What can the radical law be applied to? | Point, area, and line symbols |

Who were the first people to quantify selection features in an article? | Toepfer and Pillewizer |

What does the radical law describe? | The reduction of the amount of information, which can be shown on a map in relation to reduction in scale. |

What is the simplest form of the radical law applicable to? | The generalization of maps at the topographic scale. |

What is the equation for the simplest form of the radical law? | nf = na square root of Ma / Mf |

What does nf stand for? | # of objects, which can be shown at the derived scale |

What does na stand for? | # of objects, which can be shown on the source scale |

What does ma stand for? | scale denominator of the source map |

What does mf stand for? | Scale denominator of the derived map |

Will the result of the radical formula be smaller or larger than the source map? | Smaller |

If the source map has 22 railway line segments, and the scale is 100,000, how many railway line segments should there be on a derived map with a scale of 1:250,000? | 14 |

What aspect of generalization does the radical formulas provide information about? | quantitative aspect |

How can the simplest form of the radical law be modified for different kinds of map symbols? | By adding Cz, which is the constant of symbolic form |

How can the simplest form of the radical law be modified for different maps? | By adding Cb, which is the constant of symbolic exaggeration |

How did Toepfer and Pillewizer come up with the constant of symbolic exaggeration? | By counting objects at many scales |

Created by:
aley1