Rendering Effective Route Maps: Improving Usability Through Generalization

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Rendering Effective Route Maps Improving
Usability Through Generalization

• Maneesh Agrawala, Chris Stolte
• Stanford University
• Presented by Ken Deeter

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(No Transcript)
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General Idea

• Automatically generate a route map that has the
  same properties as a hand drawn map.
• Hand drawn maps
• Exaggerated Lengths (non-constant scale factor)
• No irrelevant information

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More Specifically

• Constant scale factor
• Road lengths on a conventional map vary in
  several orders of magnitude gt small roads and
  neighborhoods are hard to navigate with large
  maps
• Information irrelevant to navigation
• Names of locations, places, cities, etc. that are
  all far away from the route
• Takes up space that would be otherwise useful for
  showing crossroads and relevant landmarks

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Cog. Psych. Research

• Recipe for an effective route map
• Clearly communicate all turning points
• NOT
• Correct lengths
• Correct angles
• Correct shape

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Generalization Techniques

• Generalize Length
• Use more space for short roads, less for longer
  ones. Distribute based on importance, not
  physical length
• Generalize Angle
• Align roads or make room for others
• Generalize Shape
• Navigator doesnt need to know roads shape.
• Simpler roads are easier to differentiate on a
  map.

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Route Map Generation Pipeline

• Input Route data
• Process
• Shape simplification
• Road Layout
• Label Layout
• Context Layout
• Decoration
• Output Map image

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Shape Simplification

• Simplify roads but with specific constraints
• No missing intersection
• No false intersection
• No wrong turn direction
• For roads where shape is important (curvy such as
  highway ramps) be more conservative.

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Road Layout

• Formulated as a search in the space of all road
  layout configurations.
• Simulated annealing to find optimal layouts
• Requires layout scoring function, and
  perturbation function
• Perturbation modifies a length of a road by up to
  20 or orientation by 5 degrees

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Layout Scoring

• Penalize for short roads
• Penalize for change in ordering of length of
  roads
• Penalize for change in orientation from original
• Penalize for missing and false intersections
  (many tricky details.. See paper for speficics)
• Penalize for bad shape if orientation of start
  and endpoints is different, or if they are too
  close

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Remaining Layout

• Label Tries to layout labels deterministically,
  then resorts to search for conflict resolution
• Context Adds crossroad and landmark information
• Decoration global orientation arrow, explicit
  turn points,

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Output Image Size

• Estimate at first by using simple distortion.
• For small displays find orientation that takes
  best advantage of devices vertical scrolling
  capability (most routes are not square)
• At the same time try to keep north as up
• Resolution 200 pixels for routes with 10 steps
  10 pixels/step

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Evaluation

• 2200 users, voluntary feedback (self-selected)
• More than 95 percent said they would use the
  system

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Drawbacks

• Layout still fails in some cases
• Random search does not converge to optimal layout
• Sometimes impossible to stay within all
  constraints
• Not useful for long trips
• Not useful for when people get lost
• PDA displays more likely to have problems of
  overlapping labels

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Demo at mapblast.com