Geo170 Quiz #4

What data classification methods are used based on the levels of measurement?

(a measurement level describes the nature of numerical info about geographic features) - Nominal - Ordinal - Interval - Ratio Data

Isoline Maps

- A type of continuous surface map - Isoline = A line that connects points of equal value on a map. - Commonly used to show quantities that vary smoothly over the Earth's surface (think Weather maplines) - Two rules on isoline maps: ---> Intervals between isolines are equal ---> There is ALWAYS a high/low side of a particular isoline (b/c there just can't be any sides that are higher/lower at the same time) - Some maps use a progression of color lightness, color intensities, and/or color textures between each isoline.

Qualitative Change Map

- A type of map that shows the change of geographic phenomena. - Mapping change can be difficult b/c it can be hard to find symbols explicit enough to convey the correct info to the reader.

Level of measurement

- A way to describe the scaling of data within statistics - Four levels of measurement: --> Nominal (qualitative) --> Ordinal (qualitative) --> Interval (quantitative) --> Ratio (quantitative)

Limitations of the Combined Method for Quantitative maps

- As the # of variables increases, readability decreases - It's difficult to convey the relative importance of the themes/attributes on the map.

Memetic Point Symbols

- Between geometric + pictographic symbols - Generally created from a combination of geometric shapes - Could be simple or complex - Fall between geometric and pictographic - Found on tourist maps, recreational maps, airport maps, etc. - May or may not need a legend

Orientation (as applied in a qualitative thematic map)

- Can be used to create patterns that show qualitative differences for features.

Pattern Texture (when referring to quantitative maps)

- Can imply quantitative differences by density - Finer, highly-packed grid = high quantity - Loose, coarse grid = lower in quantity

Cartograms

- Cartograms distort areas in proportion to the magnitude of the variable (such as population). - This type of map makes it much easier to see the differences between areas and the distribution of the data.

How do you make a choropleth map?

- Choose the appropriate symbols to represent the quantity of area features. - Also decide how to associate data values with symbols (by grouping data into classes --> so you need data reclassification)

Color Saturation

- Color intensity - A subtle visual variable that is best used to show subtle variations.

Multivariate Quantitative Map methods

- Combined method - Multivariate point symbol - Pie/Bar charts

Ratio Data

- Consists of numerical values on a magnitude scale. - The zero point is NOT arbitrary, unlike interval data. - Zero point is CLEARLY defined and typically the point detonates the absence of the phenomenon. - It has all the properties of interval-level data, but also a natural zero value. - AND, the ratios between the two values are meaningful for ration data. Ex: Height, weight, measure of time. ---> A weight of 4 grams is twice as much weight as 2 grams.

What data classification methods are used based on what kind of geographic phenomena the data represents?

- Continuous or discrete data - Point, line, area, or volume data.

Disadvantages of Proportional Symbol and Graduated Symbol Map

- Densities/ratios/rates are hard to display w/ this type of map. - Hard to tell different circle sizes apart, esp. when a continuous sequence of symbols are used --> the human eye can't differentiate between slight variations in symbol size.

Quantitative Data

- Depicts the magnitude of things expressed in numbers. - Can be quantified, measured, compared, and used meaningfully in computations. - Think Population density, rainfall, etc.

Quantitative

- Describe any numerical information about spatial features and their relationships. - They answer questions like: How many? How large? How wide? How fast? How high? How deep? etc. --> To answer these questions, they use ordinal, interval, or ratio data.

Line Phenomena

- Describes features that follow a line without a defined width at a certain scale. - Thinks rivers, roads, etc.

Pictographic Point symbols

- Designed to look very similar to their real-world counterparts. - Very detailed symbols, so they remind map readers of the real-world features they are supposed to represent.

Shape (as applied in a qualitative thematic map)

- Different shapes imply differences in type, rather than differences in magnitude. ----> For example, a square is different than a circle, but the reader wouldn't assume the square is MORE than the circle.

Size (when referring to quantitative maps)

- Different sizes = differences in quantity - Point features: larger circles = greater quantity - Line features: wider line = bigger - Area features: more volume - greater quantity

Advantages of the Combined Method for Quantitative maps

- Effectively displays 2-3 variables and useful for inspecting individual distributions.

Color Lightness (when referring to quantitative maps)

- Implies an increase in quantity using the darkness of color.

What is the difference between surface maps and choropleth maps?

- In choropleth maps, changes are abrupt, while in CSM's, the changes are smooth.

Ordinal Data

- Includes values with order, which allows comparisons of the degree between two values. - Ex: scale of tree size, level of pain, movie ratings, etc. - Ordinal variables do have a meaningful order (unlike nominal), but the intervals/differences between the values are not necessarily equal. - There is no quantifiable numeric difference between their values, so the data is considered to be qualitative. - They show the position in a rank, but don't establish magnitude or relative proportions.

Unclassified Choropleth Maps

- Instead of grouping data values, we can also symbolize the data using continuous color intensity by assigning each data value a unique shade. - To create one, we assign a unique color/shade to a data value. - Simplest map has only two classes: above and below the median --> but when more classes are used on the map, it can become much more difficult to read.

Multivariate Point Symbols

- Two ways to use/make point symbols multi-variable. --> Single Point Symbol: - One symbol displays multiple factors/attributes - Ex: Chernoff Faces and the LA map displaying multiple factors/attributes --> Segmented Point Symbol - Divided into multiple parts, w/ each part indicating one variable. - Total magnitude for each attribute is represented using point symbols that vary in size.

Dot Density Maps

- Type of continuous surface map - Aim of a dot density map --> present an image of changing density across the region rather than giving precise locational info. - SO, in order to make a good map, one needs to determine the appropriate dot size, shape, color, etc. - Uses dots to represent data values within a polygon. - Useful method to show variations in density across a surface. - ONLY used with polygons/areas. - Each dot represents data values w/in a polygon --> it's a useful method to variations in density across a surface. -

3D Perspective Map

- Type of continuous surface map - The mapmaker needs to construct closely spaced line profiled in two directions AND perspective view to create a fishnet! - Fishnet map: Uses lines to depict the continuous surface, so the reader can see undulations in it. - You see the undulations w/in the surface, not on one line or quadrilateral. - The ability to see all locations on the map is determined by the viewpoint and the viewing angle! (both of which are chosen by the mapmaker)

Pie or Bar Charts

- Type of multivariate quantitative maps - Very effective to display multiple attributes, where each component (bar/slice) of the chart corresponds to an attribute. - Pie/Bar charts are ONLY used with polygons!

Psuedo-Contiguous Cartogram

- Typically transforms each area into a simple shape - The shape for each area is not preserved, but represented with a simple shape (circle, square, triangle, etc). - They look contiguous, but the boundaries aren't real, which is why it is called "psuedo-contiguous".

Combined method

- type of multivariate quantitative maps - Most straightforward way to make a map - Combines two or more of the mapping methods, where each method is applied to one theme/attribute.

Volume Phenomena

-Occupies a volume in space (including length, width, depth) at the scale of the map. - Think mountains, ocean trenches, etc.

Maps show us _______, NOT ___________

... Data, NOT phenomena ---> So, we need to think carefully about the data we map; how does data related to real world phenomena? - We need to classify the data first before mapping it

What are the two types of qualitative changes?

1) Change in the category of features over time at the SAME location. 2) Change over the location of a feature over time.

Flow Maps

Flow = Defined as the movement of things from one place to another... - Flow maps --> show these movements spatially using a line symbol called a flowline. - the size of the flowline is proportional to the magnitude of the flow. - Direction of the flowline also matters, b/c sometimes the ends of the lines have arrows to show direction. - The magnitude of the flow can also be shown by varying the texture, color, and color saturation/lightness.

Point, Line, Area, or Volume Data

- Geographic data can be categorized by the physical shape/dimension of geographic phenomena (i.e Point, line, volume, etc) - The classification of geographic features like point, line, area, volume, etc, only matter at a specific scale of the map.

Nominal Data

- Has no order, and only gives NAMES or LABELS to various categories. - Consists of categories used to distinguish different types of features. - These values are used to distinguish one feature/object/phenomena from another. **** THESE VALUES ARE QUALITIES, NOT QUANTITIES Ex: Gender, religion, political affiliation, jersey numbers, college major, etc. - Nominal data values aren't always descriptive - could be ZIP codes, phone #'s, etc --> but the numbers have no numerical meaning, and aren't measuring anything. Jersey # example: - They are numerical, BUT they don't imply order/convey anything about the category. - A jersey number of 15 means nothing different from one of 30.

Interval Data

- Interval data consists of numerical values on a magnitude scale that has an arbitrary zero point. - The numerical value can order from low to high, with a numeric difference between the classes. - Ex: Land elevations - the zero level is arbitrarily defined as mean sea level. ---> When looking at interval-level data on a map, we know that the numerical intervals (differences) between values are meaningful, but the RATIOS between values are meaningless. Another Ex: Farenheit scale for temperature - Equal differences on the scale represent equal differences in temperature ( a difference between a temp of 30 degrees and 20 degrees is the same as between 20 and 10 degrees). - BUT, a temp of 30 degrees is NOT 2x as warm as one of 15 degrees. Another ex: - A student who scores 90% on a test vs. a student who scores 45% probably isn't exactly 2x smarter as the 45% student.

What are the ways to map continuous surface maps?

- Isoline/Isopleth Maps - Dot Density Maps - 3D perspective maps

Line Feature Maps

- Line features like streams, roads, or boundaries can be represented with different line symbols. - Appropriate visual variables like shape, orientation, and color hue can differentiate line features of different types. - Generally, variations in color hue + shape are used to represent a greater variety of line features.

How do you tell the difference between proportional symbol and graduated symbol maps?

- Look at the legend!! Graduated Symbol Maps: --> generally have a range of data values --> AND, data are grouped in intervals, and each is associated with a certain symbol size. --> So each symbol on the map needs to have a size listed in the legend. Proportional Symbol Maps: - Symbols on the map could have a size NOT listed in the legend.

non-contiguous cartogram

- Looks exploded b/c neighboring areas don't touch - It preserves the shapes of the area as much as possible. - Each area is enlarged/reduced in proportion to it's population.

Topographic Maps

- Most common type of reference maps - Maps that use isolines to represent constant elevations. - Shows topological features including terrain elevation, water networks, boundaries, roads, towns, cities, and labels of important features.

Area Phenomena

- Occupies an area on the map - Think houses, forests, lakes, countries, and even buildings.

Thematic maps can be....

- Qualitative or Quantitative ---> Qualitative: Describe the location or distribution of a phenomenon using nominal data. ---> Quantitative: describe the magnitude or value of a phenomenon and use ordinal, interval, or ratio data.

What data classification methods are used based on how the data defines or describes the geographic phenomena?

- Qualitative or Quantitative Data

Choropleth Maps

- Represent quantitative properties of AREA features by varying the lightness and intensity of the colors. - These maps technically show density and/or rate information about area features (think population, tax rate, etc.) - They DO NOT show straightforward values, like totals. - Choropleth maps are the most common and effective theme maps.

Continuous Data

- Represents continuous phenomena that has NO defined borders, but rather a smooth transition from one value to another. - Think elevation, aspect, slope, air temp, precipitation, etc. - This type of data changes without incremental steps!

Discrete Data

- Represents discrete phenomena with distinct categories --> think districts, houses, towns, agricultural fields, rivers, highways, etc. - Another name for this type of data is categorical data. - Discrete phenomena can change abruptly, with nothing really in between.

Multivariate Thematic Maps

- They simultaneously display multiple themes or feature associations. - Typically, we use a different symbol to represent each attribute/phenomena. - When overlaying two or more types of area symbols, the most common method is to display one attribute using color hue, and the other attribute using pattern shape.

Area Feature maps

- To create area symbols that represent different types of area features --> color hue, shape, and orientation are used. - Most area features are differentiated by color, but could also have different combinations.

Advantages of Proportional Symbol and Graduated Symbol Map

- Show data occurring at points - They show absolute values (precise numbers) - The circles can be subdivided to show percentages of the whole. - Easy to make!

Reference Maps

- Show the simplest properties of geographic features in a specific area (i.e bodies of water, cities, political boundaries, etc)

Qualitative Data

- Shows categories of things expressed by means of a natural language description. - Think land cover types, soil types, language and religion, education level, etc.

Thematic Maps

- Shows one or a few themes of information for a specific area. - Generally coded, colored, or grouped for convenience. - Usually describe the physical, social, political, environmental, and cultural properties of a defined area.

Prism map

- Shows the magnitude of a theme variable/attribute by varying the heights of area based on its values.

Geometric Point Symbols

- Simple shapes (squares, circles, triangles, etc) to represent features. - Generally require a legend in order to be interpreted correctly.

Color Hue (as applied in a qualitative thematic map)

- Simply means that different colors - Symbols with different hues imply differences in quality/type. Ex: A brown tree = dead, but a green tree = alive!

Proportional Symbol and Graduated Symbol Map

- Single-theme quantitative map - Used for point features on a map - Proportional Maps: Use symbol size to represent the data value. - Graduated Maps: Use symbol size to represent groups of values (all quantitative values are grouped into intervals, and all the features w/in a class are shown w/ symbols of the same size).

What are the visual variables used in quantitative maps?

- Size - Pattern Texture - Color Lightness - Color Saturation

Point Phenomena

- Something that occurs at a point in space, defined solely by geographic location, and without width or area at the scale of the map. - It describes things like house, cities, etc, that may be too small to be represented by areas/polygons on a map for a given scale.

Contiguous cartogram

- The most common type of cartogram - The contiguity of neighbors is preserved, and the shapes are still maintained (to an extent). - But the area of the features still represents the quantity.

Isopleth Maps

- The values are ratios that only exist over areas (like population per kilometer, or crop yield per acre.) - Isopleth maps LOOK identical to isoline maps, but they show a density/ration surface where values cannot physically exist at points.

Point Feature Maps

- Use symbols that show the location of an object Point symbols can be geometric, pictographic, or memetic.

Continuous Surface Map

- Used to show quantities that vary smoothly over space - Think temperature, elevation, (sometimes) density.

What data classification methods are used if the data is organized in a digital format?

- Vector OR Rastor data.

The visual variables that effectively display qualitative differences on thematic maps are...

Shape, orientation, and color hue