names or identifies objects, such as the name of a state

- Nearly every feature will have a different name

 - Nominal Data aren't always text.

 - Usually portrayed on a map by labels.

seperates features into distinct groups or classes

 - often stored as text, but it is also possible to represent categories with numerical codes.

- Categorical data are represented by unique values maps, which give each category a different symbol.

grouped by rank based on some quantitative measure, although the measure may not be linear in scale.

-must be represented by unique values maps if the values are text, but the colors should be the same shade and give a sense of increase.

- Numeric ordinal data may be represented either with unique values maps or graduated color maps.

stores numbers that represent phenomena that fall along a regularly spaced measurement scale, such as population or rainfall.

-Equal change in interval involve equal changes in the object being measured.

-Ratio data 

- have added property that measurements are related to a meaningful zero point such that such zero indicates the absence of the thing being measured.

-Ratio data supports all four arithmetic operations

 - has a regular scale but is not related to a meaningful zero point.

-Any measuring scale that can have negative values, such as elevation and pH, must be an interval scale.

-Interval scales only support addition and subtraction

-Each class is symbolized using variations in symbol size, thickness, or color.

Proportional symbol map

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the numeric value is used to proportionally determine the size of the symbol.

-Instead of a few size classes, the map has a continuous range of symbol sizes.

Graduated color map

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aka "Chloropleth maps" - changes in hue, saturation, or intensity of color using shaded symbols

 - Such data should be normalized to the quantity per unit area when they are mapped, in order to prevent the size of the measurement unit from influencing the map appearance.

Dot density map

[image]

-Thematic rasters represent map features or quantities

- continuous rasters store values that represent  continuously varying quantity such as elevation

-Values in a raster are always numeric and may be characterized as categorical, ordinal, or interval/ratio.

-A raster  representing categorical or ordinal data is displayed using a unique values map, in whch each value of the raster receives its own color.

divides the values into a small number of bins

-similar to a graduated color map