Cartography Exam 2
Proportional Symbol Map Map in which point symbols vary in size according to differences in ____________ of an attribute (variable)
MAGNITUDE
In these maps, each area (spatial unit) is filled with a color or pattern. Typically political or administrative areas such as ____..._____. These are the maps we see most often.
census tracts, counties, states
counterpart of _______ aggregate data, usually ratio or percentage. data map for discrete spatial units
histogram
Map Aesthetics What did Keates say? Karssen's Three Elements for Map Aesthetics:
*****LOOK IN BOOK CHAPTER 12****????
What is Equal intervals Classification?
- Divides a set of attribute values into groups that contain an equal range of values. -Best on data that is evenly spread across the entire range of classes. Avoid if you have outliers or skewed/lumped data.
What is Quantiles Classification?
- Places an equal number in each class. If you have 30 counties and 6 classes, you will have 5 counties in each class. Creates attractive maps...but classes can have very different numerical ranges!
Rules for Placing Text and Graphics
- visual appearance of space between letters of all words of the same style and size must be the same -the space between letters must be seen to be less than the space between words -the space between words must be seen to be less than the space between lines separating units -the space between lines separating different units of information must be less than the space which surrounds that textural information.
Things to consider while Contrasting?
---Map on the right represents appropriate contrast ---Map on the left lacks appropriate contrast in four respects -Lightness and size of thematic symbols -Size of lines (line width) -Type size -Difference between the mapped area and the background
How can such different looking maps show the same variable?
--Cartographic reasons -Different break values -Different levels of spatial aggregation --Geographical reasons -Uneven distribution of minorities at the state scale as well as at the national scale -Concentration of minorities in cities, particularly in northern states
The four parts of Visual Weight? Explain each
--Location *Center less weighted than edges *Upper heavier then lower *Right heavier than left **Weight of an object attracts others and creates a neighborhood, thus giving direction --Size - larger is heavier --Color - Red, bright, isolated, unusual --Shape - regular shape, compact **create an axis that impart direction
Things to know about basic map design?
--Visual organization -Improve legibility -Focus attention --Maps do not have a natural sequence -Design can guide the map reader --Make the reader's job easier
Things you should know about map evaluation?
-A map should be suited to the needs of its users -A map should be easy to use. -Maps should be accurate, presenting information without error, distortions or misrepresentations -The language of the map should relate to the elements or quantities being represented -A map should be clear, legible and attractive. -Many maps would ideally permit interaction with the user allowing change updating and personalization.
PROPORTIONAL DEFINED
-Confusing terminology... Your textbook uses the term "Proportional" ArcMap uses "Proportional" or "Graduated," depending on the scaling method used -In ArcMap Proportional Symbols = Mathematical Scaling Graduated Symbols = Range-Graded Scaling
Map Composition....Purpose of Map Composition?
-Forces the designer to organize the visual material into a coherent whole to facilitate communication, to develop an intellectual and visual structure -Stresses the purpose of the map -Directs the map reader's attention -Develops an aesthetic approach for the map -Coordinates the base and thematic elements of the map—a critical factor in establishing communication -Maintains cartographic conventions consistent with good standards. -Provides a necessary challenge for the designer in seeking creative design solutions.
Design Levels on The Map?
-In GIS we often work with Data Layers -In Cartography Levels are similar, but help the map designer organize the map by importance. -A single element should never be assigned to more than one level.
legend design
-Legends for pin and dot density maps are typically very simple -A representative symbol and a definition -Legend headings are rarely required -A legend is not required on some pin maps -If symbol meaning is self evident -Include additional information if necessary -Legend Heading Total for entire area Sample densities
What are Problems with choropleth maps?
-Makes it easy to slant data to suit the cartographer's purpose (by adjusting the break values) -Creates the illusion of rapid breaks whereas data varies continuously and gradually in the real world -Allow small areas (like major cities) to overwhelm the data of large regions (like states)
Things you should know about map design?
-Map problem: what do you need to map? -Geographic representation: determining data needed and acquiring data. -Creating a base map. -Applying map design: Symbolizing features, filtering/collapsing, organizing visual elements. -Using appropriate colors. -Using appropriate text.
What is Map Design ?
-The purpose of design is to grasp and hold the attention of the user (effective communication). -The rules of map design can be taught and learned, but quality has to be acquired.
Communication and information rely on representations:
-What is communicated is a representation of the real thing -Locations in time and space are reduced to a few symbols -Communication requires simplification -The real world is infinitely complex -So representations reduce information to a manageable volume
Advantages of Dot Distribution Maps
-easy to understand -show the varying density of a phenomena -dot placement: placement of dots takes into account the distribution of other phenomena: a dot map of crop acreage would not place dots in urban areas, a dot map of population would cluster dots near urban areas, etc. Therefore, patterns are meaningful. -Allows for mapping with another distribution of some other phenomena: e.g. use multi-colored dots, or use dot maps over choropleth map. Therefore, they are good for complex maps
What is one of the earliest forms of shared information?
-hunters and gatherers reporting back -early stick maps for navigation in the Pacific -drawings on cave walls
Symbol choices
3D" Symbols We aren't good at estimating volumes Employ 3D symbols for aesthetic purposes, but don't expect the map user to estimate volumes
There are three primary methods of scaling, or sizing, proportional symbols ___________ AKA Mathematical (Directly Proportional) ___________ AKA Perceptual _____________
ABSOLUTE APPARENT RANGE GRADED
PROPORTIONAL SYMBOL SCALING Absolute?
Absolute The area of the point symbol is directly proportional to the data value Equivalent to an unclassed choropleth Legend shows representative values Difficult to interpret, because the map user can only differentiate a given number of symbol sizes—10 at most Studies indicate that map readers tend to underestimate the areas of larger symbols
Advantages/Disadvantages of Maximum Breaks?
Advantages: -Considers the distribution of the data -Easily computer using a spreadsheet -Size of gaps can be identified using a hierarchy Disadvantages: -may miss natural spatial clustering of data
Advantages/Disadvantages of Jenks Optional?
Advantages: -computer program attempts multiple solutions to natural breaks -attempts to minimize within class variance and maximize between class variance -produces classification with high accuracy Disadvantages: -complicated -difficult to understand the procedure for grouping
Advantages/Disadvantages of Equal Frequency (Quantiles)?
Advantages: -easily calculated using rank-ordered data -applicable to ordinal data -no empty classes Disadvantages: -does not consider distribution of the data -variable class width or gaps in legend -distribution unequal when division of observations by the number of classes does not result in a whole number -duplicate data values at class break requires manual adjustments -value of an observation could be closer to values in a different class than its own
Advantages/Disadvantages of Nested means?
Advantages: -easily computed -mathematically intuitive Disadvantages: -limited to 2,4, or 8 classes -does not consider distribution of the data, possibly placing majority observations in one class -not included as an option in GIS and mapping software -requires the use of User Defined in order to apply within software
Advantages/Disadvantages of Equal Interval?
Advantages: -easily understood by the map reader and straight forward -simple to compute -no gaps in the legend Disadvantages: -does not consider distribution of the data -may produce classes with zero observations
Advantages/Disadvantages of mean and standard deviation?
Advantages: -good for data with normal (bell shaped) distribution -considers distribution of the data -produces constant class intervals Disadvantages: -most data are not normally distributed but skewed in some manner -requires an understanding of basic statistic -not easily understood by the map reader
Advantages/Disadvantages of Arithmetic and Geometric Intervals?
Advantages: -good for data with significantly large ranges -break points determined by rate of change in the data Disadvantages: -Not appropriate for data with small ranges or linear trends
Color Map Symbolization
Unipolar Data (cont) -Monochromatic or Part-Spectral sequential schemes work best
Advantages/Disadvantages of User Defined?
Advantages: -provides complete flexibility for the user -break points may be defined based on spatial distribution observed by classification methods Disadvantages: -logic of legend breaks not apparent -may not consider distribution of the data -not easily repeated
Advantages/Disadvantages of Natural Breaks?
Advantages: -considers the distribution of the data -Uses groupings based on break points visible graphically -Intuitive Disadvantages: -Class breaks are subjective -Breaks are not necessarily obvious -Difficulty to determine breaks increase -May miss natural spatial clustering of data
_____________ Experiment until dots are clearly visible, not "too big," and coalesce only in the most dense
BALANCED DOT SIZE WITH UNIT VALUE
Map Composition Organization of Visual Elements?
Balance and centre -Visual impact of arrangement. harmonious arrangement around the optical centre -concern for weight and direction of objects around the 'natural' centre -unbalanced composition look random and accidental
Map Composition Balance and Visual Balance does what?
Balance involves the visual impact of the arrangement of image units in the map frame. Visual balance results from two major factors: weight and direction (size and location for the elements).
Color Map Symbolization
Balanced Data -Consists of two commentary phenomena -Diverging color schemes are appropriate
Color Map Symbolization
Bipolar Data -Have a natural dividing point (zero, mean, etc..) with values falling above or below -Diverging color schemes are appropriate
TRUE vs. CONCEPTUAL DATA Conceptual Point Data Data collected for enumeration units Symbol is placed in the _________ of polygon
CENTER
Proportional Symbol Map (cont.) The ________ is most widely used shape, but other shapes can be used
CIRCLE
Dots should __________ only in the most _______________ _______ Dot size needs to be balanced with dot value (unit value)
COALESCE DENSE AREAS COALESCENCE MEANS OVERLAP
Advantages of proportional symbol maps: They show _________ occuring at _______ They show absolute ________ (precise numbers) The circles can be _________________ to show percentages of the whole They are easy to make
DATA, POINTS VALUES SUBDIVIDED
DOT VALUE, SIZE AND PLACEMENT
Dots need to be as prominent as possible
Apparent AKA Perceptual Symbols are systematically __________ toward the higher end of the range
ENLARGED
__________: Uses the boundaries of geographic units (_________) to determine the area represented with a particular ________.
Enumeration Units counties, states, countries... shade or color
Dot Map (cont.) Map in which point symbol _____ illustrates __________ of an __________ (variable)
FREQUENCY_ DIFFERENCES ATTRIBUTE
Various symbol shapes can be used Two categories of point symbol ___________ ___________
GEOMETRIC PICTORIAL
Subjective Elements of Design (Karssen) (5)? Explain each.
Generalization - beauty of simplified shapes Symbolization - beauty of graphic representation Color - beauty of color accent and balance Layout - beauty of composition Typography - beauty of typographic appearance
3 Weakness of choropleth maps
Gives the impression that a feature or phenomenon is __uniformly distributed______ within each enumeration unit Exact values cannot be determined within a given enumeration unit The value at a particular point falls within the range of the enumeration unit's class __Larger enumeration units tend to attract more attention___ Can cause misinterpretation of data Enumeration units of uniform size and shape are most effective
dot distribution maps
If not created properly, these maps, and other maps, can be confusing. In the map you will see, dots were placed randomly to identify alligator populations in the countries of North America. What does the map you will see imply? (next slide in class!)
What is Geographic information?
Information about some place on the surface of the Earth -or near the surface -at some point in time
Advantages of Choropleth Maps
It provides an __easy way to visualize____ how a measurement varies across an area. When defining regions is important to a discussion (as in an election map divided by electoral regions), choropleths are preferred. Choropleth maps are also appropriate for indicating differences in land use, like the amount of recreational land or type of forest cover.
Map Composition Contrast and Design 5 things to remember.
Line Contrast Texture Contrast Value Contrast Variation of Detail Color Contrast
linear legend arrangement representative sybols
Linear-Legend Arrangement Symbols placed adjacent to one another Vertical or horizontal orientation Symbols placed adjacent to one another Vertical or horizontal orientation
Problems with choropleth maps
Makes it easy to slant data to suit the cartographer's purpose (______by adjusting break values__) Creates the illusion of rapid breaks whereas data varies continuously and gradually in the real world Allow small areas (___like major cities____) to overwhelm the data of large regions (_like states_)
nested legend arrangement representative sybols
Nested-Legend Arrangement Smaller symbols drawn within larger Requires less available space than linear
Each point symbol can represent One individual feature or phenomenon Called a __________ Each symbol represents a single golf course Symbols are placed where features are actually located
PIN MAP
What is Natural breaks (Jenks) Classification?
Picks breaks that best group similar values together naturally and maximizes the differences between classes
Symbol choices
Pictorial symbols Can be very effective Should be closely related to the theme Complex symbols are potentially more difficult to interpret in congested areas
What is Classifying data? What are things you would use to organize classifying data?
Process of placing data into groups that have a similar characteristic or value Break points - Breaks the total attribute range up into these intervals -Keep the number of intervals as small as possible (5-7) -Use a mathematical progression or formula instead of picking arbitrary values
labeling symbols
Proportional symbols should be labeled as ordinary point symbols
Proportional Symbol Map (cont.) ______________ in nature Point symbols are unlike those on a dot map, which have the same size and value
QUANTITATIVE
range graded. PROPORTIONAL SYMBOL SCALING
Range-Graded (cont.) Ranges are associated with a limited number of easily differentiated symbols Equivalent to a classed choropleth Employs a limited number of symbol sizes, allowing the map user to determine the general value using the legend Map-design research has provided guidelines for selecting symbol sizes that are easily differentiated Possibly the best scaling method Readers can easily discriminate symbol sizes and match them to legend symbols Especially useful for pictographic symbols It is difficult to estimate areas of complex shapes Classification can be achieved using any data classification method Doesn't work well if the map user fails to consult the legend
legend design representative symbols
Representative symbols can be arranged in two fashions Linear Nested
Each point symbol can represent (cont.) ___________ features or phenomena Called a _____________ Each symbol represents 10,000 people Symbols are not placed where features are actually located
SEVERAL DOT DENSITY MAP
Dot Map (cont.) Illustrates variations in _____________ Dot Map (cont.) Can have many dots, or just a few
SPATIAL DENSITY
Proportional Symbol/Graduated Symbol MaP... In this type of a map, a ____________ is selected, usually a _________ because it's easier to work with.
SYMBOL CIRCLE
COLOR SCHEMES
Sequential schemes (most common) Recommended for unipolar data Should increase from light to dark Darker colors should be associated with larger numbers Colors should be distinguishable from one another
Disadvantages of Graduated Symbol Maps: Densities/ratios/rates are hard to show with this map It's hard to ______________ the relationship between the _______________ circle _____
TELL, DIFFERENT, SIZES
SYMBOL CHOICES
The circle is the most widely used Compact and visually stable Users prefer over other geometric symbols Easy to construct and scale (PI r2)
TRUE vs. CONCEPTUAL DATA
The distinction is sometimes blurry Enumeration units represented at small scales are treated as points
Symbol choices
The square is a bit more awkward than the circle Blocky nature isn't as efficient with space Area of a square can be more accurately estimated
Visual Hierarchy
The visual hierarchy is the intellectual pan for the map and the eventual graphic solution that satisfies the plan.
Disadvantages of Dot Distribution Maps
There is a human tendency to underestimate density and it's easy to do with this map If dots get too dense, it is difficult to read Dot placement: computer placement of dots is often random; thus, patterns are often not meaningful if the map is misleading.
Disadvantages of Choropleth Maps
They give a false impression of __abrupt change____ at the __boundaries______ of shaded units. It can be difficult to distinguish between __different shades_____ in the maps. They have terrible problems with induction (e.g.: even though not everyone voted Republican in a state, when they color it red on a map on TV it LOOKS like everyone did) boundaries of unit areas are arbitrary sometimes (e.g.: "the South")
symbol overlap
Trial-and-error is required to produce a map with suitable symbol overlap Symbols can be differentiated by applying contrast Symbols can be differentiated by applying contrast (cont.)
TRUE vs. CONCEPTUAL DATA
True Point Data Data collected at discrete points Weather stations, seismometers, etc. Conceptual Point Data Data collected for enumeration units Symbol is placed in the ____???????_____ of polygon
Apparent (cont.) Compensates for the map user's tendency to _____________ areas of larger symbols
UNDERESTIMATE
Dot Map Map in which point symbols of _____ and _______ are used to emphasize a spatial pattern
UNIFORM SIZE VALUE
RULES OF THUMB dot density
Use limiting ancillary attributes Reduces unrealistic placement of dots by limiting where they can be placed Use data from enumeration units that are smaller than your area of interest* Use counties or census tracts when mapping a state Census tracts or block groups when mapping a county Block groups when mapping a city, etc.
Map Layout
Use of white space Fill white space with map title, legend, scale bar, source, projection information, north arrow Space map elements with equal white space
John Snow's Dot Map (1854)
Used to identify the Broad Street water pump, and halt a cholera epidemic A classic example of the use of a thematic map in service of spatial analysis The first epidemiological map
Geographic contents to be considered:
Visual balance -----> location/proportionality Visual clarity -----> generalization Visual hierarchy -----> font & symbol size Visual contrast -----> use of color and shading Context -----> selection of data layers Text -----> annotation of features
What three "W" are used at the end of the chapter concerning the Title?
What, Where, When components
Practical issues of choropleth maps?
___Choice of Intervals____ - number and their breaks equal interval, equal share (quantiles), standard deviational, ... ___Choice of color_______ important for perception of patterns misleading role of area of spatial units larger areas "seem" more important
Placement of legend definitions
adjacent to symbols, adjacent with leader lines, within symbols.
choro from choros (________) and pleth (_________)
place value
