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GIS I > Lecture 4 (Generalization and Geovisualization) > Flashcards

Lecture 4 (Generalization and Geovisualization) Flashcards

1
Q

Why Generalization?

A

“You are here!” TOO MANY DETAILS/ TOO FEW DETAILS/ Finally! Just the right amount of information

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2
Q

Can a map be perfect?

A
  • The real world is infinitely complex
  • A map must always approximate, GENERALIZE, abstract, or simplify
  • Simple and quick answer: No!
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3
Q

Implement Generalization

A
  • Two fundamental types of geographic phenomena
  • Generalization for DISCRETE OBJECTS is easy to understand: POLYGON can be generalized (simplified) to a POINT
  • But, how to generalize CONTINUOUS FIELDS?
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4
Q

Generalization of Continuous Fields

A
  • Many geographic phenomena are conceptualized as fields (exactly one value of the phenomenon exists at every point on the Earth surface - e.g. elevation and precipitation)
  • In principle, a field can take a different value everywhere (An infinite amount of info, Tobler’s Law helps by virtually guaranteeing that variation will be smooth and slow over space)
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5
Q

Six Ways of Representing a Field (See Printed Paper)

A

a) regularly spaced sample points
b) irregularly spaced sample points
c) rectangular cells
d) irregularly shaped polygons
e) irregular network of triangles
f) polylines represent countours

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6
Q

Map generalization

A
  • Reduces complexity from the real world
  • Retains spatial and attribute accuracy (at the specified scale level)
  • Accounts for map purpose and scale
  • Provides more useful ‘information’ or more efficient communication and presentation
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7
Q

Methods of generalization

A

McMaster and Shea (1992) identified 10 distinct types of generalization rules.

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8
Q

10 distinct types of generalization

A

Simplification, Smoothing, Collapse, Aggregation, Amalgamation, Merging, Refinement, Exaggeration, Enhancement, Displacement

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9
Q

Object Types in Vector Format

A

From (Point, Node to Vertex, Arc/ i.e., Line To Node) Point Feature

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10
Q

Simplification

A

Weeding - Remove points in the outline of a polygon to create a SIMPLER SHAPE.

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11
Q

Smoothing

A

Replace the SHARP and COMPLEX parts and make the result LOOK SMOOTHER

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12
Q

Collapse

A

Replace an area object by a COMBINATION OF POINT AND LINE OBJECTS

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13
Q

Aggregation

A

Replace a large number of distinct symbolized objects by a smaller number of new symbols

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14
Q

Amalgamation

A

Replace several area objects by a SINGLE AREA OBJECT

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15
Q

Merging - common form of generalization

A

Replace several line objects by A SMALLER NUMBER OF LINE OBJECTS from their most similar neighbors.

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16
Q

Refinement

A

Replace a complex pattern of objects by a selection ones, and preserves THE PATTERN’s GENERAL FORM

17
Q

Exaggeration

A

Relatively enlarge an object to PRESERVE ITS CHARACTERISTICS when changing the map scale.

18
Q

Enhancement

A

Emphasize THE PHYSICAL SIZES OR SHAPES of symbols, and preserve the PATTERN’s GENERAL FORM.

19
Q

Displacement

A

Move THE OBJECTS FROM THEIR TRUE POSITIONS, but still preserve their visibility and distinctiveness.

20
Q

Map Generalization

A

Simplifies the complexity and provides us the clear, useful and correct information

21
Q

How to design a map?

A

Inset map, Map Body, Scale, Legend, Title, North Arrow, Projection, Data Source, Author

22
Q

GOAL of Map Design

A 
Primary Goal 
- Share information
- Highlight patterns and processes
- Illustrate results
Secondary Objective
- attracting our audiences
PROVIDE A GOOD-LOOKING, SIMPLE, AND ELEGANT MAP TO MEET ITS PURPOSE
23
Q

Principles of Map Design

A

Purpose - one or multiple, what/ how to display
Reality - reduce the complexity in map
Available data - raster or vector
Map scale - quality of map, level of detail
Audience - different backgrounds/ expectations
Conditions of use - where to use it
Technical limits - digital map or hard copy

24
Q

Digital Map v Paper Map (See Printed Sheet)

A

GIS is a flexible medium for the production of many types of maps

25
Q

Digital Map in cyber space

A

In addition to traditional static mapping, more and more online mapping features are available. For example: Street views (Bing Maps, Google Maps), Draggable driving directions, Birds Eye View (Oblique photographs) etc.

26
Q

Street Views

A

Street view car, snowmobile, trike, Grand Canyon Trekker

27
Q

Augmented-Reality Maps

A

Augmented Reality GIS Maps (2007), TED Presentation (2010), Google Eyes (2012)

28
Q

Map Compositions

A

Map body, title, legend, scale, direction indicator, map metadata, inset/ overview map

29
Q

Direction Indicator - Grids

A

A grid is a network of parallel and perpendicular lines superimposed on a map.

30
Q

Direction Indicator - Graticules

A

Graticule is a network of longitude and latitude lines on a map that relates points on a map to their true locations on the Earth.

31
Q

Inset Map

A

Shows more detailed area and additional maps that map body didn’t display.

32
Q

Overview Map

A

Used to identify the map body’s general location in a coarser scale

33
Q

Geovisualization - 3D visualization

A
  • Easier to interpret data - for common publics
  • Demonstrate your proposals in a more natural and direct approach - for both specialists and general publics
  • Visualize data in 3D to identify patterns not apparent in 2D (Volume of reservoir, visibility analysis)
34
Q

Geovisualization - Geographic Visualization

A
  • The creation and use of visual representations to facilitate THINKING, UNDERSTANDING, AND KNOWLEDGE CONSTRUCTION about human and physical environments, at geographical scales of measurement.
  • Geovisualization is used to explore, analyze, synthesize, and present spatial data.
  • Increase the interactions between users and digital maps - VGI and PPGIS
  • Improve the Virtual Reality (VR)
35
Q

Augmented Reality Map/ Geovisualization for Forestry/ Virtual Reality/ 3D CitiesEngine

A

3D appearance/ UGA Project/ Cityscapes in 3D

36
Q

Digital Elevation Model (DEM)

A

DEM is the digital cartographic representation of the elevation of the terrain at regularly spaced intervals in x and y directions using z-values referenced to a common vertical datum (USGS)
- Elevation, Slope, Hillshade, Contour, Aspect, Viewshed

37
Q

DEM v DTM (T = Terrain)

A
  • DEM (DSM)s - measure the terrain elevations for ground positions at regularly spaced horizontal intervals (in addition, DEMs include BUILDINGS, TREES and ANY OTHER OBJECTS OVER THE EARTH’S SURFACE)
  • A Digital Terrain Model (DTM) measures the heigh of the earth’s surface ONLY.
38
Q

Metadata

A

“data about data”

What we look at to find many things, such as where our data was collected, its extent, the units, and others

39
Q

On-the-Fly

A

This means ArcMap can display data stored in one projection as if it were in another projection

GIS I (7 decks)

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