Week 7: Mapping Techniques and Data Representation

• A process transforms quantitative data into ordinal classes, known as discretization or classification.
• Choropleth maps work best with normalized data but may not always be suitable
• Complex spatial phenomena often require multiple maps for representation.

Week 7

• Critical analysis of maps is crucial to understand what information they may omit.
• Isarithmic maps represent areas of constant elevation using contour lines.
• Closer spacing of contour lines indicates a steeper slope.
• Topographic base layers offer context to contour lines by showing terrain features like valleys, peaks, and ridges.
• Choropleth maps shade or color areas uniformly based on data values, ensuring each area is separate and non-overlapping.
• Proportional symbol maps scale point symbols to represent values.
• Graduated symbol maps classify proportional symbols.
• Cartograms adjust the size of an area based on its value.
• Dot density maps use dots to represent a value within an area, showing density distribution and variation.
• Isoline/isarithm maps connect points of equal value with lines (isolines) to represent continuous data.
• Isometric maps use isolines or color shading to depict 3D areas of equal value for subjects like temperature and pressure; data occurs at points.
• Isopleth maps deal with data over geographical areas and are only for relative values; data occurs over geographical areas (conceptual point data).
• Isobath describes depth below sea level.
• Isohypse (contour) describes elevation above sea level.
• Isotherm measures temperature.
• Isobar indicates pressure.
• Isospecie indicates density of species.
• Isochrone indicates travel time from a given point.

Week 8

• Dot maps use the number of items a dot represents as the dot value and the dot size to represent size of each dot.
• Dot guidelines:
  • The area should contain at least 2 or 3 dots with the least quantities.
  • Dots should start merging in the highest density area.
  • Dot value should be simple (e.g., 5, 100, 5000).
  • The map’s overall impression shouldn't be too accurate or general.
  • Dots may need to be larger or have zoom capability in virtual maps to prevent squares.
  • Dots don’t mark an exact spot.
  • Dot placement should be guided by filters or additional knowledge in mapping software.
  • Urban areas typically have more dots than rural areas
• Size represents numerical quantities in proportional symbols.
• Proportional symbols are easy to calculate with lines and are very common with points.
• Proportional symbols can be problematic, but interesting with polygons.
• The eye can only see a few classes when using Proportional Symbols.
• Flux mapping visualizes movement, flow, or transformation of elements like people, goods, energy, or information.
• Line size often represents movement intensity, volume, or frequency.
• Thicker lines may denote stronger or more frequent flows, while thinner lines might indicate weaker or less frequent ones.
• Material elements are tangible (physical) and immaterial elements are intangible (conceptual).
• Flux representation can be shown with symbols, points, lines, or arrows that represent flight paths or data transfers.
• Point-to-Area Flux displays how localized flows broaden into a citywide network (e.g., traffic from intersections).
• Qualitative Flux describes flow characteristics, like a city's changing "feel" due to tourism.
• Quantitative Flux indicates numerical values like migration statistics or internet bandwidth.
• Graduated symbols are part of a class
• Proportional Symbols are unique
• Steps to define symbol sizes:
  • Calculate the radius (or side) of the symbol surface based on the data.
  • Apply a constant to these values to fit to the map.
  • Create a values list, then find the square roots of those values, then work from the square roots list rather than the original list.
  • Pick a constant maximum symbol size– like a 2 cm diameter circle– where the largest symbol represents the largest square root list value, like 4500.
  • The symbol size = (constant) x (value / maximum value).
  • Design the symbol for that shape, maintaining proper proportions regardless of the size of the circle’s diameter, the square's side, triangle, or icon height.
• Mathematical scaling constructs circle areas directly proportional to data
• The size of proportional symbols does not scale to their mathematical size in Perceived Scaling
• Accurately scaled circles allow users to measure the symbol and gather an precise data response, and less confusion arises when symbols get measured directly to the value, both which the benefits of Mathematical Scaling.
• The disadvantages of Mathematical Scaling happens because humans underestimate areas with perception
• Perceptual Scaling causes a user to inaccurately perceive values of the symbols, seeing the bigger symbols are smaller than they are truly.
• Perceptual Scaling causes Symbols to be perceived more accurately which is Perceptual Scaling
• If a user were to measure the symbols, they would evaluate the incorrect value, scaling is based on the average person and does not include all users, both are Disadvantages of Perceptual Scaling.
• Cartographers use visual variables to provide redundancy within a symbol
• Two or more visual variables can portray a geographic feature, which is known as Redundant symbols.
• Cartograms distort reality and change the size and exaggerate the variable on an attribute value to show information.

Color

• Additive color primaries mix light (RGB) on computer monitors, while subtractive primary pigments mix pigments (CMYK) in printing.
• Each pigment reflects/absorbs part of the light
• Color perception is affected by:
  • Viewer age
  • Color saturation (contrast)
  • Size of type
  • Color-blindness (reds and greens may be confusing to some, so it is better to use reds and blues or greens and blues)
• Color synthesis types:
  • Physical (impact of light on color formation)
  • Chemical (mixture of substances to produce color)
  • Physiological (how the eye perceives color)
  • Psychological (connotation associated with color)

Week 9

• Thematic maps focus on a subject/theme (like population density, climate, or land use) and use colors, symbols, or patterns to highlight spatial patterns and relationships; reference maps emphasize location and accuracy and thematic maps emphasize data visualization and analysis.
• Data can be acquired by comparing raw totals (proportional symbols) and standardized data (choropleth map).
• Bivariate mapping is a multivariate mapping form encoding two data variables into a single product to investigate a relationship.
• Inter-symbol encoding involves two independent symbols.
• Graphically representing multiple visual variables simultaneously through geometric dimensions is Inter-symbol encoding.
• “Thematic map combinations also can be understood.
• Multiple variables are placed into each symbol and Graphically representing multiple visual variables within a single discrete symbol in Intra-symbol encoding.
• Bivariate choropleth maps should have two related in creating
• The maps go further than just showing two variables on bivariate maps because they show where the two variables agree or disagree.
• Bivariate maps shouldn’t be the choice if no expectation exists that links the two variables.
• The number of classes in a bivariate choropleth is larger than the sum of classes in each variable because it shows the agreement between variables.
• The bivariate choropleth map usually has n2 classes when individual variables have n classes.
• A 9-class bivariate map can be made by combining two-3-class univariate maps.
• Inter-symbol encoding is use of separate symbols for each variable
• Integrating both variables into a single symbol is Intra-symbol encoding
• Multivariate mapping is a way to encode cartographic visual variables from multiple data variables into a single product, to investigate a relationship.

Multivariate Dot Maps

• Dot Density map of the Hispanic population of New York City.
• Each dot represents one person.
• The visual impression of the overall density of the dots is the variable terrain of the overall population of Hispanic persons.
• The hue tied to each point, each person, represents their national origin.
• Chernoff faces are useful for multivariate symbols.
• Humans detect subtle differences in facial features well.

Data Collection

• Primary data includes records of observations made by machines (like a recording thermometer) or the map makers themselves, like GPS, smartphones, crowdsourcing, existing maps, remote sensing imagery
• Secondary data comes from primary data, like scanned and digitized paper maps, federal/regional/local government data and public domain data providers/NGOs
• Tertiary data is assembled secondary data and maps often are made from other maps
• Layers for secondary and tertiary data are increasingly available as open data, free and easily accessible with common mapping and GIS software.
• Qualitative is categorical and has Nominal differences in kind.
  • Qualitative uses symbolization, like symbols, pictographs, icons, and color hue differences, and electoral college wins by state (Democrat vs. Republican).
• Quantitative has Ordinal and Interval (no absolute zero), and ratio data (absolute zero)
  • Quantitative is the differences in amount
• Estimating the number of same-sex couples and comparing Phenomenon vs number are done using Total numbers vs Densities
• Calculate Average vs Rates
• Critiquing a map includes making sure it reaches its goal(s)
• Look for accurate and relevant data.
• Consider if the map scale is adequate, If the coordinate system is appropriate, and The map title should be clear and coherent
• Map design should reflect the intellectual hierarchy in the visual hierarchy.

Week 10

• GIS (Geographic Information System) is a system that supports collecting, storing, transforming, displaying/representing, analyzing, and displaying spatial data from the real world.
• GIS collects, manages, analyzes, and displays data using technology while providing a spatial data analysis unlike data analysis platforms.
• A common framework for showing possible questions that a GIS can answer was initially defined within Geography:
  • What is Where?
  • Why There?
  • Why care?
• Finding hazards and patterns are done in a Hazard Scattering Map
• Density maps are useful when areas of interest vary, as in census tracts and urban areas and display population density in regions like East Asia and the Indian Ocean.
• GIS is used to show what is happening in an area, find areas adjacent to a phenomenon and detecting change.
• Spatial Analysis helps quantify patients location and provide a visual of the most and least utilizing:
  • An Overlaying Capability
  • Proximity Analysis
  • Multi-criteria overlay analysis Seven factors have been identified in the model to place residents in Residential Suitability Model
• Existing Land Use (20%)
• Legally Restricted Areas & Health Detrimental Areas (20%)
• Distance to Bus Routes (15%)
• Distance to Shopping (10%)

GIS Data Types

• Vector data stores real-world objects (points, lines, polygons) as specific, discrete shapes with appended attribute information in a related database, which is why made can be made in GPS, Public and Private Geodatabases,Graphic Design Software

• Raster Data stores real world objects as a matrix or grid of cells

• Continuous geographic features can be represented by dividing the world into discrete square/rectangular cells in a grid.

• Every cell has a value for representing a location characteristic (ex: temperature/elevation as Satellite imagery).

• The value represents the entire cell square, yet, for certain data (elevation), the value can be a measured value at the center.

• Length/width of a cell is cell resolution, where higher resolution raster files equal smaller cells.

• JPEG, TIFF, PIX, and Photoshop also use raster data for image editing.

• Vector data can be converted to raster data, although the nature of data will still be different between the two.

• Vector data: discrete, possess edges and borders, and create points, lines, and polygons.

  • We think of vectors and points –> lines –> polygons (simple features)
  • Discrete features include attributes.

• Raster data: continuous, is a grid of cells having values, generally has no attributes associated with each cell. -Raster data is primarily what you might be interested in using.

Week 11

• A map is never an objective representation of reality.
• Implicit biases can be seen in world maps, such as Europe being at the center, North/South divisions, and Up/Down divisions.
• Promoting Alternative Worldviews encourages people to reconsider their mental map and recognize the arbitrariness of placing “north” on top.
• Projections retain countries/continents general shapes, and Latitude/longitude grid patterns stay consistent.
• Deforms include: Relative size distortions, especially near the poles, due to the projection's inherent issues (like the Mercator's exaggeration of landmasses at higher latitudes).
• Recapping on projections, Mercator preserves but not area, Gall-Peters safeguards, and Robinson is a but of both.
• Cartographic Critique includes mapping practices and processes (how we make maps, what tools we use), the politics of mapping (who directs, designs and distributes mappin projects), use and how is it used the world.

Counter Mapping

• Counter-mapping involves communities adopting state formal mapping techniques to crete their own alternates to those used used by the government.