Relief Portrayal
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Transcript of Relief Portrayal
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Relief Portrayal
January 23, 2006Geog 258: Maps and GIS
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Outlines
How relief is portrayed?1. Absolute-relief portrayal methods2. Relative-relief portrayal methods3. Combining relief portrayal methods4. Dynamic relief portrayalDigital data for relief portrayal5. 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
Relief models
Raised relief topographic map
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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 RelativeContour Physical
modelIsobath Perspective
viewsHypsometric 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 RelativeContour Physical
modelIsobath Perspecti
ve 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