CARTOGRAPHY AND VISUALIZATION I

Lesson 2

By Mwaura Joshua | @openmapsCo on Twitter

Lesson 2: Visualization in GIS

Visualization in GIS | Introduction

• Visualization is a technique for creating images, diagrams, or animations to communicate
• Since the dawn of man , visualization through visual imagery has been an effective way to communicate both abstract and concrete ideas
• Map remains a traditional medium geographic visualisation
• Geo-visualization interactive visualization, using a set of tools and techniques that supports geospatial data analysis

Components of Visualization

• Visualization depends on the interaction of:
• Database - store information
• Display - visualisation medium
• Human visual system - reception
• Brain - process information

Cartographic Communication Concepts

• Cartographic Communication Model
• The visual thinking/visual communication curve referred to as "swoopy" from DiBiase (1990)

Visualization | Cartographic Process

• Recommended series of steps you should follow to design a map {unmapped data to map form}
• Define the purpose and meaning of the map;
• interpret the requirements of the user
• determine what needs to be communicated
• determine how to best facilitate communication of your ideas, and create a narrative for the map
• Choose the scale for the map
• the map scale is the ratio of the map distance to the earth distance
• map scale operates along a continuum from a large scale to a small scale
• Large scale [1:0 <> 1:600,000], medium scale [1:600,001 <>1:2,000,000], & small scale [1:2,000,001 <> ∞]
• the amount of detail you can show a map is directly dependent upon scale, the selection of map scale is possibly the most important decision a cartographer makes

Visualization | Cartographic Process

• Determine the map format, printing limitations, and economics of reproduction of the map product
• What kind of a map?
• What type of a map?
• How will the map be displayed?
• How much will it cost to create the map?
• Abstract and generalize the data to prepare it for placement on the map
• Only information that is potentially meaningful to the context should be included
• Cartographers select & organize information necessary to communicate concept to map reader
• Cartographers reduce the amount of detail on a map to create a simple visual image

Visualization | Cartographic Process

• Abstraction & generalization methods
• Selection
• Classification
• Simplification
• Symbolization-Use recommended conventions
• Design the map layout
• Carefully consider the placement and design of the 12 map elements
• Consider the scale, size, and shape of the primary object being mapped

Visualization | Abstraction & Generalisation

• Each operation results in a reduction of the amount of specific detail, yet the end result presents the map reader with enough information
• On the other hand, excessive generalization may lead to no transfer of knowledge
• A balance must be struck by the cartographer

Visualization | Cartographic Generalisation

• Types of cartographic generalization
• graphic & conceptual
• Graphic generalization is characterized by;
• simplification, enlargement, displacement, merging and selection
• maintains symbology
• affects geometric component of geospatial data
• Conceptual generalization is characterized by;
• merging, selection, symbolization and enhancement
• symbology may change
• affects attribute component of geospatial data

Visualization | Cartographic Generalisation

• left: Graphic generalization right: Conceptual generalization

Generalization | Selection

• Selection involves early decisions on;
• geographic space to be mapped
• map scale, map projection
• which data variables are appropriate for the map’s purpose
• sampling methods to be employed
• selection requires the cartographer to be familiar with the map’s content, nature of the data to be mapped

Generalization | Classification

• Classification refers grouping of identical or similar features to enhances communication
• Individuality and detail of each element is lost
• reduces the complexity of the map image
• helps to organize the mapped information
• In thematic mapping, classification can be carried out with qualitative or quantitative information

Generalization | Simplification

• Selection and classification are examples of simplification, but simplification may take other forms as well
• e.g. smoothing of natural or man-made lines on the map to eliminate unnecessary detail
• purpose of this map is simply to show connectivity between two points, not to illustrate the road’s precise locational features

Generalization | Symbolization

• In mapping, symbolization is required because its not possible to create a reduced image of the real world without devising a set of symbols that stand for real-world things
• Two major classes of symbols are used for thematic maps;
1. Replicative
• designed to look like their real-world counterparts
• they are used to stand only for tangible objects
• basemap symbols are usually replicative in nature
2. Abstract
• take the form of geometric shapes, such as circles, squares, and triangles
• Symbolization process is shaped by the influence of scale

Generalization | Read on

• The human vision system:
• vision
• perception
• cognition
• behaviour

--- End of Lesson 2---

That’s it!

Queries about this Lesson, please send them to: jmwaura.uni@gmail.com

***References***

• Mapping, Society, and Technology, Steven Manson
• Web Cartography, Map Design for Interactive and Mobile Devices, Ian Muehlenhaus
• Web Cartography, Menno-Jan Kraak and Allan Brown, ITC
• Cartography, Thematic Map Design, Borden D. Dent
• GIS Cartography, A Guide to Effective Map Design, Gretchen N. Peterson
• Thematic Cartography and Geovisualization, Terry A. Slocum et.al