Relief%20Portrayal

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Relief Portrayal

• January 23, 2006
• Geog 258 Maps and GIS

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Outlines

• How relief is portrayed?
• Absolute-relief portrayal methods
• Relative-relief portrayal methods
• Combining relief portrayal methods
• Dynamic relief portrayal
• Digital data for relief portrayal
• DEM (Digital Elevation Model)

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1. Absolute-relief methods

• Provides relief in a numeric scale
• You can determine exact value of elevation or
  water depth at individual points from this kind
  of map
• Designed to give precise measurements
• You can measure slope from this kind of map
• You can create profile from this kind of map
• Common methods include
• Contours lines of equal elevation
• Isobath lines of equal water depth
• Hypsometic tints color-coded contour interval

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Contours

• Think of contours as lines obtained by cutting
  terrain horizontally with imaginary planes in
  equal intervals
• Contours are lines of equal elevation

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Types of contours

• What would terrain look like inside depression
  contour?
• Not all contours are labeled index contour is
  labeled, shown as thick lines

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What is contour interval from this map?
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Isobaths

• Lines of equal water depth

Further questions Any difference compared to
contour map?
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Hypsometric tinting

• Space between contour lines is color-coded

Does this look better than a contour map? Why do
you think so?
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Hypsometric tint
Is color coding scheme good?
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Hypsometric tint
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Spectral color progression
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Vignetted hypsometric tints
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2. Relative-relief methods

• Designed to give a general impression of relative
  heights of landform rather than its exact values
  at individual points
• Focused on providing realistic presentation of
  relief
• Different ways to create 3D effect
• Commonly used methods include
• Physical relief model raised relief
• Perspective view oblique vantage point
• Relief shading imaginary light source

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Physical model of relief

• Physical 3D model of relief

Raised relief globes
Raised relief topographic map
Relief models
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Perspective views

• Creates 3D effect with oblique vantage points

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Perspective views
Landscape drawings
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Perspective views
Fishnet maps (terrain profiles)
Block diagram
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Relief shading

• Creates 3D effect using an imaginary light source

Shaded relief map
Vertical aerial photo
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3. Combining relief methods

• Absolute methods are good for making
  measurements, but it is hard to have a general
  sense of terrain variation
• Relative methods are good for gaining a general
  impression, but it does not give precise
  measurements
• Why not combine both?

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Which methods are combined in this map?
Absolute Relative
Contour Physical model
Isobath Perspective views
Hypsometric tinting Relief shading
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Which methods are combined in this map?
Absolute Relative
Contour Physical model
Isobath Perspective views
Hypsometric tinting Relief shading
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Which methods are combined in this map?
Absolute Relative
Contour Physical model
Isobath Perspective views
Hypsometric tinting Relief shading
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Which methods are combined in this map?
Absolute Relative
Contour Physical model
Isobath Perspective views
Hypsometric tinting Relief shading
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Which methods are combined in this map?
Absolute Relative
Contour Physical model
Isobath Perspective views
Hypsometric tinting Relief shading
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Which methods are combined in this map?
Absolute Relative
Contour Physical model
Isobath Perspective views
Hypsometric tinting Relief shading
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Which methods are combined in this map?
Absolute Relative
Contour Physical model
Isobath Perspective views
Hypsometric tinting Relief shading
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Which methods are combined in this map?
Absolute Relative
Contour Physical model
Isobath Perspective views
Hypsometric tinting Relief shading
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4. Dynamic relief portrayal

• Putting relief portrayal into motion
• Can gain dynamic impression of landform
• Animated methods
• A sequence of maps is animated ? detect changes
• A series of images taken from different vantage
  points are combined to create animation ?
  fly-over
• Interactive methods
• You can choose the location, vantage points, and
  so on
• Demo
• http//www2.jpl.nasa.gov/srtm/
• http//geology.asu.edu/reynolds/topo_gallery/topo
  _gallery.htm
• http//www.truflite.com/

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5. Digital Elevation Model

• Some maps can be made by hand
• Relief globe, hachures, block diagram
• These days maps are increasingly generated by
  computers
• Shaded relief map, profile map, fly-over
• Combining methods are easily manipulated
• Basis of computer-generated terrain mapping is
  Digital Elevation Model (DEM)
• DEM stores elevation or water depth in regularly
  sampled points
• DEM can be thought of as varying elevation values
  stored in matrices