Efficient and effective result presentation with GIS

1. GIS in the Sciences ERTH 4750 (38031) Efficient and effective result presentation with GIS Xiaogang (Marshall) Ma School of Science Rensselaer Polytechnic Institute Tuesday, Apr 16, 2013

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

3. Contents • GIS and maps • The visualization process • Visualization and strategies • The cartographic ‘toolbox’ • data characteristics • representation of these characteristics • Examples, how to map: • qualitative data • quantitative data • (terrain or statistical) elevation, time • Map cosmetics: the finishing touch • Map dissemination

4. 1 GIS and maps • In a GIS environment, maps can be used to: • Inputfor GIS • CommunicateGIS results • Supportspatial analysis • Maps are not only final products (output)! Data Capture and Preparation Storage and Maintenance Data Presentation Manipulation and Analysis

5. Map Characteristics • Main characteristics of maps • 1. Maps provide answers (in graphical form) to questions related to the three basic components of geographic data • geographic location (Where?) • thematic attributes (What?) • time (When?) “Where did the students of a department come from?”

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

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

8. Main characteristics of maps • 2. Maps offer abstract representations (models) of reality, that are: • simplified • classified • symbolized Details in the aerial photograph are omitted from the map. For example, cars are not symbolized in the map.

9. Main characteristics of maps • 2. Maps offer abstract representations (models) of reality, that are: • simplified • classified • symbolized Features in the photo are classified using predefined criteria. For example, roadways are classified as major or minor roadways.

10. Main characteristics of maps • 2. Maps offer abstract representations (models) of reality, that are: • simplified • classified • symbolized Symbolization is used to highlight differences in features. Major and minor roadways are symbolized differently.

11. Main characteristics of maps • 3. Maps are representations at scale Scale: ratio between distance on the map and corresponding distance in reality Maps that show much detail of a small area are called large-scale maps.

12. Main characteristics of maps • 3. Maps are representations at scale Scale: ratio between distance on the map and corresponding distance in reality Maps that show less detail of a large area are called small-scale maps.

13. a little more about scale • Scale indications • verbal • e.g. one-inch-to-the mile • representative fraction • e.g. 1 : 100 000 • graphical (scale bar) • suitable in digital environments!

14. Scale indications • verbal • e.g. one-inch-to-the mile • representative fraction • e.g. 1 : 100 000 • graphical (scale bar) • suitable in digital environments!

15. Scale indications • verbal • e.g. one-inch-to-the mile • representative fraction • e.g. 1 : 100 000 • graphical (scale bar) • suitable in digital environments! • Digital graphical scale • Advantage of scale bar in digital environment is that its length changes when zooming in or out

16. Definition of a Map • Now we can have a definition for the map • 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. These maps can be perceived visually, on a computer screen or printed map

17. 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. These maps are stored in a database

18. 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. A tactile map is a map for blind or seriously visually impaired users, it can be perceived by touch instead of visually.

19. Types of Maps • Traditional distinction in maps • topographic maps • accurate representation of the Earth’s topography • thematic maps • one or more particular themes are emphasized A topographic map of the New York state.

20. Traditional distinction in maps • topographic maps • accurate representation of the Earth’s topography • thematic maps • one or more particular themes are emphasized • Less relevant distinction in a digital environment (a) (b) (a) New York County Map (b) New York Rivers Map

21. 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) 2 dimensional (flat) representation of the ITC building and surroundings.

22. 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) 3 dimensional (flat + height) representation of the ITC building.

23. 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?) 4 dimensional (flat + height +time) representation of the ITC building, at three moments in time during its construction.

24. 2 The visualization process • Maps are the result of a visualization process

25. 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) An algorithm can be used to smooth lines and improve the appearance of features.

26. 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) Rules tell us to use proportional symbols to display absolute quantities.

27. 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) Traditionally water is represented in blue.

28. 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 thinking • keywords: interaction, dynamics

29. Geovisualization • Two main strategies of visualization: exploration, presentation • private visual thinking: involves an individual playing with the spatial data to determine its significance • public visual communication: concerns maps aimed at a wide audience • If maps are visually explored, we also talk about geovisualization

30. Geovisualization is accelerated by: • the possibility to generate maps at any stage in geoinformationprocessing • hard- and software developments • new output media • changing needs / expectations of users • availability of abundant data, from different sources

31. 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. Information 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.

32. 4 The cartographic ‘toolbox’ • Analysis of the characteristics of data • What 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 ? The 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.

33. Measurement scales are linked to the way in which people perceive visual variables

34. Basic elements of a map: • point symbols • line symbols • area symbols • text • These elements can all be variedin appearance

35. Bertin’s visual variables • Bertin’s visual variables: an elementary way in which point, line and area symbols can be graphically varied. • size • color • value (lightness) • grain/ texture • orientation • form/shape

36. 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 representation

37. 5 Examples • How to map: • qualitative data • absolute quantitative data • relative quantitative data • terrain elevation • thematic data in 3D • time series

38. How to map qualitative data • What is the common denominator of the data? Watersheds • What is the nature of the data? qualitative (nominal) • Solution: Colorsof equal visual weight or brightnesswhich allow the user to quickly differentiate between watersheds.

39. How NOT to map qualitative data Map image suggests differences in importance, but that is NOT what you want to communicate Misuse of bright color results in attention to specific area on the map

40. How to map absolute quantitative data • What is the common denominatorof the data? number of inhabitants • What is the nature of the data? absolute quantitative • Solution: symbols varying in size

41. How NOT to map absolute quantitative data Value does not enable estimation of differences in absolute quantities, only order. User is left asking "here there is more, but how much?" The applied four-color scheme makes it impossible to infer whether red represents more populated areas than blue. No perception of order.

42. How to map relative quantitative data • What is the common denominator of the data? Number of inhabitants/sq km • What 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)

43. How NOT to map relative quantitative data The values tints are out of sequence, the user will perceive wrong order (e.g. darkest is not highest in density) No perception of order

44. How to map the terrain elevation • Different methods to map terrain elevation: • Contours • Layer tints • Shaded relief • 3D view Cartographic technique where lines connect points of equal elevation at a selected interval.

45. Different methods to map terrain elevation: • Contours • Layer tints • Shaded relief • 3D view A cartographic technique of showing relief on maps by coloring in different shades those parts which lie between selected levels.

46. Different methods to map terrain elevation: • Contours • Layer tints • Shaded relief • 3D view Cartographic technique where lines connect points of equal elevation at a selected interval.

47. Different methods to map terrain elevation: • Contours • Layer tints • Shaded relief • 3D view Cartographic technique where lines connect points of equal elevation at a selected interval.

48. 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'

49. How to map time series • Single static map: specific graphic variables and symbols are used to indicate change or represent an event • Series 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.

50. 6 Map cosmetics: the finishing touch • Additional information marginal info (or metadata): makes the map more usable • Adding text improves the identification of features • Contrast improves overall map legibility