Lecture07

Lecture07 - The number of features and labels we can...

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1 Geography 12: Maps and Spatial Reasoning Lecture 7: Map generalization Professor Keith Clarke Let’s start here 1:1550 1:6227
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2 1:12450 1:24910 1:46390 1:89060
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3 1:172 910 1:344 200 About 1:500 000 About 1:2M
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4 About 1:5M While we zoom • Detailed to generalized • Features drop off • Jaggies to blurry • Extent increases • Earth model matters more • Different levels of interpretation possible • Hard to convert measurements with RF Some common map scales Round numbers makes life easier • 1:24 000 • 1:50 000 • 1:100 000 • 1:62 500 • 1:63 360 • 1:250 000 • 1:500 000 •1 :
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5 What happens as we generalize? • Selection • Simplification • Combination • Displacement • Exaggeration Simplicity, VA 17SQB2898706830 Just enlarging doesn’t work Intermediate Scales: Simplicity gone!
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6 On OSM Coarse scales Selection
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Unformatted text preview: The number of features and labels we can display depends on the space available! Need to select features to display by some criterion, e.g. population size of villages Need to carefully assign and place labels Dawson City, 1 327 Montreal, 1 620 693 Simplification 7 Bend, TX: Simplification Combination Fairhope, AL A complex process 8 Displacement: Separation Point, WY Displacement Hwy 217 Hwy 217 to canal = 10m 9 Without displacement, lines are not separable 10 m at 1:100,000 = 0.1 mm Solution: Move the lines! 10m becomes 200m! Exaggeration Attribute generalization 10 Summary: generalization is necessary when scale changes These things happens when we generalize Selection Simplification Combination Displacement Exaggeration...
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This note was uploaded on 12/27/2011 for the course GEOG 12 taught by Professor Gautier during the Fall '08 term at UCSB.

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Lecture07 - The number of features and labels we can...

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