Data ata Generalization Ge e a at o and a d Mapping app g GEOG380 Fall 2009
Outline `
Scale Generalization
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Term Project
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Project j Memo 1 ((PM1))
The actual map making `
Decisions on ` ` ` ` ` ` ` `
Reproduction method, printing (ch. 13) Types of map (ch. 1&3) Projection (ch. 7&8 ) Measurement, Symbolization (ch. 3&5) Generalization & Mapping – Today (ch. 6) Design (ch.11&12) Color (ch. 10) Intellectual hierarchy (ch.13)
Implications of scale `
Watch the following slide and think about: ` `
What happens to objects in the map? How does the change influence potential map usages?
A cartographic dilemma `
Smaller cartographic scales mean that map extent is (more or less area/detail?), which leads to: ` `
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N d for Need f generalization li i to: `
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Overcrowding & Collision Features (e.g., point and line symbols) require more space than they do in reality Reduce complexity
However, should maintain ` ` `
Space & attribute accuracy Aesthetic quality Logical hierarchy
Generalization `
The process of reducing the amount of detail in a map in a meaningful way `
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“the selection and simplified representation of detail appropriate to the h scale l and/or d/ purpose off the h map”” (ICA 1973)
The basic Th b i principle i i l iis to emphasize h i important i things hi and d omit less important ` ` ` `
Ensure readability E d bili Preserve geographic context Be faithf faithfull to t realit reality Avoid complexity (too much information)
Figure 6.2 (Solcum et al. 2009)
Generalization operations `
Important: nomenclature is not fixed and these categories can be contested ` ` ` ` ` ` ` `
Selection Simplification Smoothing Displacement Enhancement C ll Collapse Merging Cl ifi ti Classification (O (Oct. t 8th and d 13th)
Selection
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Is the feature necessary to make your point? Will removing of the feature ` ` `
make the map harder to understand? make more important features clearer? make the map less noisy?
Simplification
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Weeding out unnecessary detail Can you simplify ` ` ` `
and still recognize the features? without removing vital information? and make features more noticeable? and make the map less noisy?
Smoothing
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Can you smooth a feature ‌ ` ` `
without losing its character? and still be able to recognize it? and make the map less noisy?
Displacement
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Are features interfering? Will displacement ‌ ` ` ` `
make features easier to distinguish? lead to confusion because of the move? make the map look less cluttered? (e.g, road maps)
Enhancement / Exaggeration
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Do you know enough to enhance a feature? Will enhancement ‌ ` ` `
increase understanding? make the feature easier to recognize? possibly lead to misunderstanding?
Dimension change / collapse
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Does dimensional change ‌ ` ` `
remove unnecessary detail? affect how features are understood? help p to make the mapp look less cluttered?
Merging
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Keeping old classes creates too many/small units ` `
Merge classes into new, higher level classes Need to consider the semantics of symbols
Decide the level of generalization `
To deal with errors such as ` ` ` ` `
Intersections where intended Lines entered twice Areas closed Over and undershoots Polygons too small, lines too close
Overgeneralization `
Data from different sources may have the problem
(Slocum et al. 2009)
Example `
mapshaper.org
Generalization in several dimensions `
There is a cognitive part to this as well! `
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Generalization is often a holistic combination of several operations, previously done unspecified in the head of the cartographers t h
Conceptual / Semantic generalization ` `
Needs N d expert knowledge k l d about b ffeatures on the h map E.g. classification of data `
A way of generalization or simplification in which details are lost, lost but we can structure the message for communication
Specific evaluation criteria and points of the course ` `
1. Total points of the course: 100% = 500 points 2. In In-class class work & Homework (30% of total points of the course: 150 points) ` ` ` ` ` `
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3 Term 3. T project j and d related l d workk (40% off totall points i off the h course: 200 points) i ) ` ` ` `
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PM1 (25 points) PM2 (50 points) PM3 (50 points) Final presentation (75 points)
4. Quiz and Test (15% of total points of the course: 75 points) ` ` `
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Map presentation (30 points) Worksheet1 (15 points) Worksheet2 (30 points) Worksheet3 (30 points) Worksheet4 (20 points) Worksheet5 (25 points)
Test1 (25) Test2 (25) Quiz (25)
5. Final exam ((15% of total ppoints of the course: 75 ppoints))
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Project Memo1 (PM1)
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For next time `
Ch. 11&12