IAT 355 Visual Analytics Spatial

Lyn Bartram

Some slides adapted from April Webster, 2008, CS 533, UBC Spatial Channels Spatial Layouts Arranging Values Space Express Parallel Regions Rectilinear Separate • We use given spatial layouts Radial when the spatial order semantics and Align Spacefilling relationships are 1D of primary importance. 2D Dense

Given Use • Spatial layout is used as the Geographic layout Fields substrate. scalar

IAT 355 | Visualizing Spatial Data

• Spatial layout is given in the data

• Geometry • Maps and GIS • Georefencing/coding • Spatial fields • Isocontours/lines

IAT 355 | Maps Geographic Data

• Long history of • Making maps • Most common form of derived geometric data • Projections (3D->2D) • Filtering, aggregation and detail • Language of visual marks • Maps encode non-spatial data onto spatially defined regions • Area/shape • point

IAT 355 | Maps GIS (Geographic Information System)

• An "information system“ that works with data referenced by spatial/geographic coordinates • dB for modeling and storing data • Tools for operating and displaying the data • observations about spatial features, activities or events, definable in space as points, lines, or areas. • Georeferencing and geocoding • link geographic location data with attribute data • ?find all left handed hockey players who play within 100 miles of Vancouver

IAT 355 | Maps Geographic Visualization

• Cartographic visualization is a relatively new development in cartography • information visualization and exploratory data analysis

IAT 355 | Maps http://www.informationweek.com/software/information-management/microsoft-debuts-cloud-based-power-bi/d/d-id/1113764?image_number=2 A GIS primer: spatial data

• Raster – Grid • “pixels” • a location and value • Satellite images and aerial photos are already in this format • Vector – Linear • Points, lines & polygons • “Features” (house, lake, etc.) • Attributes • size, type, length, etc.

IAT 355 | Maps A GIS stores information as a collection of thematic layers that can be linked together by geography

• Layer is a collection of geographic objects that are alike or that have the same class • Same dimensionality • Association or Relationship • Layers may be features or surfaces • Features have shape • Surfaces have numbers

IAT 355 | Maps Spatial/geographic data types

• Discrete objects • Points, lines, and areas • Biological organisms • Human-made objects • Countable • Persistent through time, perhaps mobile • Fields • Properties that vary continuously over space • Value is a function of location • any attribute type, including direction

IAT 355 | Maps Georeferencing

• Reference is either explicit (such as latitude and longitude coordinates), or implicit such as an address, road name, or postal code • Unique, linking information to exactly one location • Shared, so different users understand the meaning of a georeference • Persistent through time, so today’s georeferences are still meaningful tomorrow • Georeference can be globally or locally unique • City Hall

IAT 355 | Maps Georeferences Measurements

• Metric • measures of distance from fixed places • E.g., distance from the Equator or from the Greenwich Meridian • Relative ordering • E.g. street addresses in most parts of the world order houses along streets • nominal • Place names do not involve ordering or measuring

IAT 355 | Maps Georeferences cont.

• Postal/zip codes • Linear measures • Point + offset • Roads, rivers, rail, etc • Cadasters (property boundaries)

• Latitude and longitude

IAT 355 | Maps THE I2Sim project (JIIRP)

• Goal: investigate interdependencies between infrastructures and the consequent effects in an earthquake

• Test case: UBC campus

IAT 355 | Maps 1. Develop a physical model

• Buildings, networks, roads

IAT 355 | Maps 2. Incorporate a damage model

• Damage model based on several attributes:

• Cost • Survival • Structural integrity

IAT 355 | Maps 3. Add topology

IAT 355 | Maps IAT 355 | Maps 4. Identify interdependencies

IAT 355 | Maps 5. Operations

• Identify operational dependencies

IAT 355 | Maps Is this familiar? What does it show?

IAT 355 | Maps Is this familiar? What does it show?

D. Arno Peters, 147

Why every world map you are looking at is wrong

IAT 355 | Maps Projections: how can a flat map describe locations on a sphere/ellipse?

Parallels Prime Meridian Meridian Prime

Equator Meridians Prime Meridian Meridian Prime

IAT 355 | Maps Distortions

§ Any projection must distort the Earth in some way

§ Two types of projections are important in GIS • Conformal property: Shapes of small features are preserved: anywhere on the projection the distortion is the same in all directions • Equal area property: Shapes are distorted, but features have the correct area • Both types of projections will generally distort distances

IAT 355 | Maps “no flat map can be both equivalent and conformal.”

IAT 355 | Maps map : Gestalt principles

• Closure • Common Fate • Continuity • Figure-Ground • Proximity • Similarity • Smallness/Area • Symmetry

IAT 355 | Maps Howard, Cartographic Design, American River College Size matters

• Hans Meihoefer (1969) performed studies related to circle sizes • Helped determine the minimum size differences required for map users to distinguish one circle from another

Howard, Cartographic Design, American River College Visual Hierarchy

Inverted (incorrect) Visual Hierarchy

Based on an Inverted Intellectual Hierarchy • Frame and neat lines • Data source and notes • Scale and north arrow • Base information • Title, subtitle, and legend • Thematic symbols and type

Howard, Cartographic Design, American River College Visual Hierarchy

Correct Visual Hierarchy

Based on a Correct Intellectual Hierarchy • Thematic symbols and type • Title, subtitle, and legend • Base information • Scale and north arrow • Data source and notes • Frame and neat lines

Howard, Cartographic Design, American River College Visual variables

• Qualitative/nominal Identity tasks

IAT 355 | Maps Howard, Cartographic Design, American River College Visual variables Must be learned!

• Quantitative (interval,ratio) Magnitude tasks

IAT 355 | Maps Howard, Cartographic Design, American River College Howard, Cartographic Design, American River College CONTRAST

Inappropriate Contrast Appropriate Contrast FIGURE-GROUND

• To accentuate points and/or lines • Make the points or lines darker than their surroundings

Base information has been lightened through “screening” FIGURE-GROUND

• To accentuate areas • Make the area lighter than its surroundings

The surrounding area has been darkened FIGURE-GROUND

• Land-Water Contrast • A special case of figure-ground accentuating a lighter area • The “ground” is water FIGURE-GROUND

• Making an area lighter than its surroundings is not always appropriate • When the mapped area is dense with areal thematic symbols (esp. when color is limited to shades of gray)

Areal thematic symbols provide enough contrast between the mapped area and its surroundings

Gray background might be confused with thematic symbols FIGURE-GROUND

• Multiple layers of importance can be represented • Features can be assigned relative importance, based on relative proximity to the map user

Circles act as figures in relation to countries (which act as ground)

Countries, while subordinate to circles, act as figures in relation to water (which acts as ground)

Countries appear further away than circles, yet closer than water FIGURE-GROUND

• Alternative methods of establishing figure-ground that accentuates areas • Imposition on a graticule • Vignette Thematic Maps in Information Visualization

• Chloropleth maps • Colour • Textures

• Cartograms • Projections • Distortions

• Narrative maps • • Iconification

IAT 355 | Maps Chloropleth Maps

• Most common infovis maps • Each area/region filled with colour or texture representing some variable • Nominal • Ownership • Electoral vote • Quantitative • %

IAT 355 | Maps IAT 355 | Maps IAT 355 | Maps IAT 355 | Maps Advantages of chloropleth map

• 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.

IAT 355 | Maps Disadvantages of chloropleth map

• gives a false impression of abrupt change at the boundaries of shaded units. • It can be difficult to distinguish between different shades in the maps. • 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”)

IAT 355 | Maps Correct data choice is critical

Population Population Density

IAT 355 | Maps Digital Image maps

• Uses pixels instead of block regions • Typically used with satellite and sensor data

• Deforestation in the Congo

IAT 355 | Maps Symbol maps

• Symbols (often circles) visually manipulated for value

IAT 355 | Maps IAT 355 | Maps Advantages of symbol maps

• Easiest to make • Show actual point of data occurrence • Show absolute values • Symbol can be multidimensional (glyph)

Crowdsourced repair reporting, FixMyStreet.com

IAT 355 | Maps Disadvantages of symbol maps

• Densities and ratios hard to show

• Difficult to tell relations between different symbol values • Between • Among

IAT 355 | Maps Isoline/Isopleth/Isosurface maps

• These maps are used to show quantities that vary smoothly over the earth’s surface. • two forms: • Lines of equal value (“iso” means equal) or • Ranges of similar value

IAT 355 | Maps Isolines showing temperature values oliviasmapcatalog.blogspot.ro/2012/03/isotherms.html Derived Spatial Data Geometry

• Isolines: • A line on a map, , or graph connecting points of equal value • Contour lines • Isosurface • 3D surface connecting “slices” of equal value

IAT 355 | Maps Visualization of NEXRAD data for the May 22, 2011 Joplin, MO tornado overlaid on Google Earth: NOAA Advantages of iso-maps

• Good for showing gradual change over space • avoid the sudden changes which boundary lines produce. • Temperature, for example, is something that should be mapped using isopleth maps, since temperature exists at every point (is continuous), yet does not change abruptly at any point (like population density may do as you cross into another census zone).

IAT 355 | Maps Disadvantages of isopleth maps

• They are not suited for showing discontinuous or 'patchy' distributions • A large amount of data is required for accurate drawing

IAT 355 | Maps Dot distribution maps Wheatear bird breeding, UK, 2008

• Use dots to show quantity in given areas

IAT 355 | Maps Advantages of dot maps

• easy to understand • show the varying density of a phenomena • dot placement 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.

IAT 355 | Maps Dot maps

• Allows for mapping with another distribution of some other phenomena • Good for complex maps

IAT 355 | Maps Height field (dot) maps

IAT 355 | Maps Disadvantages

• There is a human tendency to underestimate density - 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

IAT 355 | Maps Cartograms

• Geometry or spatial layout is distorted to represent a variable (quantitative) • show the amount of something by increasing or decreasing the size of the area in which the “something” is found

IAT 355 | Maps Cartograms

• Any projection is a distortion ??

IAT 355 | Maps Cartograms

• Population Mark Newman, Cartograms, 2009

IAT 355 | Maps Cartograms

• GDP Mark Newman, Cartograms, 2009

Japan !!!

IAT 355 | Maps Advantages of cartograms

• Good at showing relationships between attributes of spatial units • emphasizes weights and concentrations

• provocative

IAT 355 | Maps Disadvantages

• Distortions are difficult to parse/decode for accurate value

• Area variability means comparative judgments are difficult (as opposed to more geometrically defined areas that can be decomposed into singular spatial features)

IAT 355 | Maps