0 Maps are the principle means of displaying spatial data

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2 Why cartography? 0 Maps are the principle means of displaying spatial data 0 Exploration: visualization, leading to conceptualization of patterns and processes. (Chap 13) 0 Communication: convey information and findings that are difficult to express verbally. (Chap 12)

3 Exploration and Communication 0 A 3D-perspective map that illustrates the relative spatial density of reported pirate incidents in the Gulf of Aden for Suspected hijacked vessel locations and traffic patterns through the Gulf of Aden were identified using satellite imagery. 0 This work was done by UNOSAT in support of the ongoing humanitarian operations across the Horn of Africa and in response to the UN Security Council Resolution 1816 (2008) adopted June 2, 2008, and IMO resolution adopted November 29, 2007, calling for continued monitoring of Somali pirate activity. 0 Courtesy of UNITAR/UNOSAT,

4 Cartographic communication Synthesis Presentation Confirmation Exploration

5 Why cartography? To become a complete GIS analyst, you need to become familiar with the basic elements of cartography and, in particular, map design.

6 Map design criteria 0 What is the motive, intent or goal of the map? 0 Who will read the map (the audience)? What are Map design criteria? 0 How will the map be used: stand alone, in a report, or simply for your viewing? What things / circumstances would require you to design a map differently? Real world Conceptualization Measurement & representation Analysis Interpretation, validation & exploration

7 Cartographic transformations Three stages in the transformation of the Earth's surface from reality to map can be recognized: 0 Primary: geometric -- map projections Going from 3-D reality to 2-D cartographic representation requires several transformations. 0 Secondary: semi-geometric -- geoid to ellipsoid What would they be? (Datums) 0 Tertiary: generalization 0 Generalization is a non-reversible process, and therefore must be carefully considered.

8 Generalization 0 Generalization has four main components: 0 Simplification: excluding unwanted, enhancing desired 0 Classification: reduces complexity (qualitative, quantitative) 0 Symbolization: implicit or explicit, mimetic or abstract 0 Induction: logical inference--integration of parts into a whole What are the main concepts / requirements / processes involved in generalization? 0 Mandates & the scale at which the data will be displayed are a prime consideration.

9 Generalization Simplification Classification Both processes reduce the detail

10 Simplification Impact of simplification tolerance Simplification routines are available in most GISystems. The first image: ungeneralized data set, the second: generalized at an 0.1 foot tolerance, the third: generalized at a 10 foot tolerance. A necessary process as the scale changes ArcMap s simplify line ArcMap s Generalization toolset

11 Classification 0 Categorical (nominal, ordinal) vs numerical (interval, ratio) data [NOIR] 0 Categorical classification: mostly qualitative 0 Numerical classification: quantitative 0 Number of classes? (4-6 is considered best)

12 Classification schemes 0 Dividing up data: numerical classification 0 Exogenous schemes 0 Arbitrary schemes (e.g., equal interval) 0 Ideographic schemes (e.g., natural breaks, quantiles) 0 Serial schemes (e.g., standard deviation) When looking at numerical data, what ways of grouping the data can you think of? 0 Unclassified schemes 0 You should always explore your data (e.g., histograms) and try different class schemes before settling on one. Know your data!

13 Symbolization components (PGEs) In creating symbols, what can you vary? Can you identify ways in which graphic components can be varied in order to distinguish different graphic elements? (Such as allowing a reader to distinguish different lines, different areas.) Primary Graphic Elements Is the data quantitative or qualitative? A useful site that explains statistics.

14 Bertin s graphic primitives, extended from seven to ten variables (the variable location is not depicted) [Info here] PGEs You must also consider how the spatial primitives (point, line, area) interact with the Primary Graphic Elements (PGEs). Source: MacEachren 1994 (from Visualization in Geographical Information Systems, Hearnshaw H.M. and Unwin D.J. (eds.). Reproduced by permission of John Wiley & Sons, Ltd.)

15 0 Abstract vs mimetic 0 (Implicit vs explicit) Qualitative data symbolization

16 Ternary plots

17 Visual hierarchy Other cartographic concerns, such as the visual hierarchy, are also important. The proper use of type is also very important.

18 Every map must contain some fundamental elements Inset map Scale Author North Arrow Map Body Data Source All maps should be enclosed by a neat line. Title Grid Legend Projection Depending on the scale, you may or may not need a grid and an inset map.

19 Map design is an art It is easy to make a map, but making a great looking map... requires consideration of all of the elements, and a sense of design.

20 Dasymetric maps Dasymetric maps use the intersection of two datasets to obtain a more precise estimate of a spatial distribution. For example, census tracts often contain large tracts of land whereon people cannot live (e.g., parks, industrial areas). Excluding those areas when determining statistics such as population density can make a significant difference to the values.

21 Summary 0 Cartography is both an art and a science. 0 Maps are fundamental to any GIS project. 0 Modern advances in GISoftware make it very easy to produce both good and bad maps. 0 Any map is just one of all possible maps. 0 Complex maps can be difficult to understand.

22 Summary 0 We have only scratched the surface with respect to the elements of cartography that are important in presenting the results of your GIS-based analyses. 0 The quality of the map will determine, to a large extent, the reception of your work. 0 A poorly produced map suggests that the analyses were also poorly handled. 0 A quality map suggests that the analyses were also done properly and with due care.

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