Efficient and effective - PowerPoint Presentation

Slide1

Efficient and effective result presentation with GIS

Xiaogang (Marshall) MaSchool of ScienceRensselaer Polytechnic InstituteTuesday, Apr 16, 2013

GIS in the Sciences

ERTH 4750 (38031)Slide2

Acknowledgements

This lecture is partly based on:Blok, C., 2006. Data visualization. E-lecture of the Distance Course Principles of GIS. ITC, Enschede, The Netherlands2Slide3

Contents

GIS and mapsThe visualization processVisualization and strategiesThe cartographic ‘toolbox’data characteristicsrepresentation of these characteristicsExamples, how to map:qualitative dataquantitative data(terrain or statistical) elevation, timeMap cosmetics: the finishing touchMap dissemination3Slide4

1 GIS and maps

In a GIS environment, maps can be used to:Input for GISCommunicate GIS resultsSupport spatial analysisMaps are not only final products (output)!4Data Capture and Preparation

Storage and Maintenance

Manipulation and Analysis

Data PresentationSlide5

Map Characteristics

Main characteristics of maps1. Maps provide answers (in graphical form) to questions related to the three basic components of geographic datageographic location (Where?)thematic attributes (What?)time (When?)5“Where did the students of a department come from?” Slide6

Main characteristics of maps

1. Maps provide answers (in graphical form) to questions related to the three basic components of geographic datageographic location (Where?)thematic attributes (What?)time (When?)6“What is the type of land use?” Slide7

Main characteristics of maps

1. Maps provide answers (in graphical form) to questions related to the three basic components of geographic datageographic location (Where?)thematic attributes (What?)time (When?)7“When did the longest coast line occur?” Slide8

Main characteristics of maps

2. Maps offer abstract representations (models) of reality, that are:simplifiedclassifiedsymbolized8Details in the aerial photograph are omitted from the map. For example, cars are not symbolized in the map.Slide9

Main characteristics of maps

2. Maps offer abstract representations (models) of reality, that are:simplifiedclassifiedsymbolized9Features in the photo are classified using predefined criteria. For example, roadways are classified as major or minor roadways.Slide10

Main characteristics of maps

2. Maps offer abstract representations (models) of reality, that are:simplifiedclassifiedsymbolized10Symbolization is used to highlight differences in features. Major and minor roadways are symbolized differently.Slide11

Main characteristics of maps

3. Maps are representations at scaleScale: ratio between distance on the map and corresponding distance in reality11Maps that show much detail of a small area are called large-scale maps.ScaleDistance on mapDistance in reality

1:5,000Large scale1cm

50m

1:1,000,000

Small scale

1cm

10kmSlide12

Main characteristics of maps

3. Maps are representations at scaleScale: ratio between distance on the map and corresponding distance in reality12Maps that show less detail of a large area are called small-scale maps.ScaleDistance on mapDistance in reality1:5,000

Large scale1cm50m

1:1,000,000

Small scale

1cm

10kmSlide13

a little more about scale

Scale indicationsverbale.g. one-inch-to-the milerepresentative fractione.g. 1 : 100 000graphical (scale bar)suitable in digital environments!13Slide14

Scale indications

verbale.g. one-inch-to-the milerepresentative fractione.g. 1 : 100 000graphical (scale bar)suitable in digital environments!14Slide15

Scale indications

verbale.g. one-inch-to-the milerepresentative fractione.g. 1 : 100 000graphical (scale bar)suitable in digital environments!Digital graphical scaleAdvantage of scale bar in digital environment is that its length changes when zooming in or out15Slide16

Definition of a Map

Now we can have a definition for the mapA map is:a representation or abstraction of geographic reality; a tool for representing geographic information in a way that is visual, digital or tactile.a reduced and simplified representation of (parts of) the Earth’s surface on a plane.16These maps can be perceived visually, on a computer screen or printed mapSlide17

A map is:

a representation or abstraction of geographic reality; a tool for representing geographic information in a way that is visual, digital or tactile.a reduced and simplified representation of (parts of) the Earth’s surface on a plane.17These maps are stored in a databaseSlide18

A map is:

a representation or abstraction of geographic reality; a tool for representing geographic information in a way that is visual, digital or tactile.a reduced and simplified representation of (parts of) the Earth’s surface on a plane.18A tactile map is a map for blind or seriously visually impaired users, it can be perceived by touch instead of visually.Slide19

Types of Maps

Traditional distinction in mapstopographic mapsaccurate representation of the Earth’s topographythematic mapsone or more particular themes are emphasized19A topographic map of the New York state.Slide20

Traditional

distinction in mapstopographic mapsaccurate representation of the Earth’s topographythematic mapsone or more particular themes are emphasizedLess relevant distinction in a digital environment20(a) New York County Map(b) New York Rivers Map

(a)

(b) Slide21

Map dimensions

You can distinguish types of maps based on the number of dimensions used for the representation:Flat (2D)Flat + Height (3D)Flat + Height + Time (4D)212 dimensional (flat) representation of the ITC building and surroundings.Slide22

You can distinguish types of maps based on the number

of dimensions used for the representation:Flat (1D, 2D)Flat + Height (3D)Flat + Height + Time (4D)223 dimensional (flat + height) representation of the ITC building.Slide23

You can distinguish types of maps based on the number

of dimensions used for the representation:Flat (1D, 2D)Flat + Height (3D)Flat + Height + Time (4D)Flat + Height + Time + Scale (5D?)234 dimensional (flat + height +time) representation of the ITC building, at three moments in time during its construction.Slide24

2 The visualization process

Maps are the result of a visualization process24Slide25

Cartographic Tools

Visualization methods and techniques are applied using cartographic ‘tools’:functions(e.g. algorithms)rules(e.g. generalization, cartographic grammar)habits or conventions(e.g. water is represented in blue)25An algorithm can be used to smooth lines and improve the appearance of features. Slide26

Visualization methods

and techniques are applied using cartographic ‘tools’:functions(e.g. algorithms)rules(e.g. generalization, cartographic grammar)habits or conventions(e.g. water is represented in blue)26Rules tell us to use proportional symbols to display absolute quantities.Slide27

Visualization methods

and techniques are applied using cartographic ‘tools’:functions(e.g. algorithms)rules(e.g. generalization, cartographic grammar)habits or conventions(e.g. water is represented in blue)27Traditionally water is represented in blue.Slide28

3 Visualization and strategies

‘Visualization’ has several meanings:generic: to make info visible (presentation in graphical form)more specific: to use sophisticated computer technology and ‘toolboxes’ to make data/info visible for specific use: visual exploration this process is often called:scientific visualization: meant to stimulate thinkingkeywords: interaction, dynamics28Slide29

Geovisualization

Two main strategies of visualization: exploration, presentationprivate visual thinking: involves an individual playing with the spatial data to determine its significancepublic visual communication: concerns maps aimed at a wide audienceIf maps are visually explored, we also talk about geovisualization29Slide30

Geovisualization

is accelerated by:the possibility to generate maps at any stage in geoinformation processinghard- and software developmentsnew output mediachanging needs / expectations of usersavailability of abundant data, from different sources30Slide31

Cartographic visualization process

The cartographic communication process, based on “How do I say what to whom, and is it effective?”Information loss or gain: Information derived by the map user is not the same as the information that the cartographic communication process started with.31Information loss refers to that fact that not all info put into the map by the map maker is (usually) extracted by the user. Gain refers to the fact that, because of background knowledge or experience, uses might also understand (gain) information that is not really included in the map. Slide32

4 The cartographic ‘toolbox’

Analysis of the characteristics of dataWhat is the common ‘denominator’? Used for the title of the map (theme, area, year)What is the nature of the data or What are the measurement scales ?32The common denominator refers to a common label for all the attributes/attribute values that are mapped (here: geological units). The nature of this data, geologic units, is qualitative and is measured on a nominal scale.Slide33

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Measurement scales are linked to the way in which people perceive visual variablesSlide34

Basic elements of a map:

point symbols line symbols area symbols textThese elements can all be varied in appearance34Slide35

Bertin’s visual variables

Bertin’s visual variables: an elementary way in which point, line and area symbols can be graphically varied.sizecolorvalue (lightness)grain/ textureorientationform/shape35Slide36

The visual variables enable observers to perceive:

what belongs together, or is of equal importance (e.g. all red symbols represent danger)order(e.g. the population density varies from low to high, represented by light and dark color tints, respectively)quantities(e.g. symbols changing in size with small symbols for small amounts) an instant overview of the whole representation36Slide37

5 ExamplesHow to map:

qualitative dataabsolute quantitative datarelative quantitative dataterrain elevationthematic data in 3Dtime series37Slide38

How to map qualitative data

38What is the common denominator of the data? WatershedsWhat is the nature of the data? qualitative (nominal)Solution: Colors of equal visual weight or brightness which allow the user to quickly differentiate between watersheds.Slide39

How NOT to map qualitative data

39Map image suggests differencesin importance, but that is NOTwhat you want to communicateMisuse of bright color resultsin attention to specific area onthe mapSlide40

How to map absolute quantitative data

What is the common denominator of the data? number of inhabitantsWhat is the nature of the data? absolute quantitative Solution: symbols varying in size40Slide41

How NOT to map absolute quantitative data

41Value does not enable estimation ofdifferences in absolute quantities,only order. User is left asking "herethere is more, but how much?"The applied four-color schememakes it impossible to infer whetherred represents more populated areasthan blue. No perception of order.Slide42

How to map relative quantitative data

What is the common denominator of the data? Number of inhabitants/sq kmWhat is the nature of the data? relative quantitative Solution: Value has been used to display the density from low (light tints) to high (dark tints)42Slide43

How NOT to map relative quantitative data

43The values tints are out of sequence,the user will perceive wrong order(e.g. darkest is not highest in density)No perception of orderSlide44

How to map the terrain elevation

Different methods to map terrain elevation:ContoursLayer tintsShaded relief3D view44Cartographic technique where lines connect points of equal elevation at a selected interval.Slide45

Different methods to map terrain elevation:

ContoursLayer tintsShaded relief3D view45A cartographic technique of showing relief on maps by coloring in different shades those parts which lie between selected levels.Slide46

Different methods to map terrain elevation:

ContoursLayer tintsShaded relief3D view46Cartographic technique where lines connect points of equal elevation at a selected interval.Slide47

Different methods to map terrain elevation:

ContoursLayer tintsShaded relief3D view47Cartographic technique where lines connect points of equal elevation at a selected interval.Slide48

How to map the thematic data in 3D

Statistical (socio-economic data) can also be represented a an elevated surface. Here, the municipalities in the province of Overijssel are elevated proportionally to their number of inhabitants. The resulting map is called a 'prism map'48Slide49

How to map time series

Single static map: specific graphic variables and symbols are used to indicate change or represent an eventSeries of Static Maps: A single map in the series represents a ‘snapshot’ in time. Together, the maps depict a process of change.Animated map: Change is perceived to happen in a single image by displaying several snapshots after each other, just like a video.49Slide50

6 Map cosmetics: the finishing touch

Additional information marginal info (or metadata): makes the map more usableAdding text improves the identification of featuresContrast improves overall map legibility50Slide51

Additional information marginal info (

or metadata): makes the map more usableAdding text improves the identification of featuresContrast improves overall map legibility51Slide52

Additional information marginal info (

or metadata): makes the map more usableAdding text improves the identification of featuresContrast improves overall map legibility52Slide53

6 Map dissemination (output)

Map design is influenced by:data characteristics & user strategies (see before)output medium, e.g., paper or screen mapsScreen maps:often smallerlegend is not always visibleand they enable:access to a data baselinks to other dataembedding in multimediadynamics and interaction53Slide54

Web maps

The Web as output medium increases the functions of maps:insight in spatial data (traditional role)interface to additional information / servicespreviews of data that can be acquiredClassification of maps on the WebStatic mapsDynamic maps54Slide55

Some historical maps of interest

55Leo Belgicus, a map of the low countries drawn in the shape of a lion, by Claes Jansz. Visscher (II), 1609Slide56

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Netherlands - Principal Industries, from Map No. 76863, by the U.S. Central Intelligence Agency, 1970Slide57

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Monthly Average Temperature, from The National Atlas of the United States of America, 1970. p.102-103Slide58

Sites for maps of interest

http://www.lib.utexas.edu/maps/ 58Slide59

Summary

Role of map in a GIS environment: more than just outputBasics: how to translate characteristics of spatial data into symbols on a map, with particular attention to:analysis of the measurement scale of the datameasurement scales can be linked to perception properties of visual variablesselection of those variables that best translate the nature of the dataAfter translation of the data, the map has to be finalized to make it usable (taking care of visual contrast, adding text, marginal information)Finally the map is disseminated to users, e.g. via hardcopies or the Web59Slide60

Reading assignments

for this weekMapInfo Professional 11.0 User GuideChapter 12 Stylizing your map for presentations and publishing Chapter 16 Working with data from a web service60Slide61

Next classes

Friday class:Lecture: Dr. Gavin Schmidt, " What are climate models good for?"When: Friday, April 19, 2013 4:00 PM - 5:00 PMWhere: EMPAC Concert HallNext TuesdayGuest lecture: Dr. David Rossiter, Advanced topics in point pattern analysis61