Transcript Relief portrayal - DePaul Geography

Relief Portrayal
January 23, 2006
Geog 258: Maps and GIS
Outlines
How relief is portrayed?
1. Absolute-relief portrayal methods
2. Relative-relief portrayal methods
3. Combining relief portrayal methods
4. Dynamic relief portrayal
Digital data for relief portrayal
5. DEM (Digital Elevation Model)
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
Contours
• Think of contours
as lines obtained
by cutting terrain
horizontally with
imaginary planes
in equal intervals
• Contours are lines
of equal elevation
Types of contours
• What would terrain
look like inside
depression contour?
• Not all contours are
labeled: index contour
is labeled, shown as
thick lines
What is contour interval from this map?
Isobaths
• Lines of equal water depth
Further questions:
Any difference compared
to contour map?
Hypsometric tinting
• Space between contour lines is colorcoded
Does this look better
than a contour map?
Why do you think so?
Hypsometric tint
Is color coding scheme good?
Hypsometric tint
Spectral color progression
Vignetted hypsometric tints
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
Physical model of relief
• Physical 3D model of relief
Raised relief globes
Raised relief topographic map
Relief models
Perspective views
• Creates 3D effect with oblique vantage points
Perspective views
Landscape drawings
Perspective views
Fishnet maps (terrain profiles)
Block diagram
Relief shading
• Creates 3D effect using an imaginary light source
Shaded relief map
Vertical aerial photo
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?
Which methods are combined in this map?
Absolute
Relative
Contour
Physical
model
Isobath
Perspective
views
Hypsometric Relief
tinting
shading
Which methods are combined in this map?
Absolute
Relative
Contour
Physical
model
Isobath
Perspective
views
Hypsometric Relief
tinting
shading
Which methods are combined in this map?
Absolute
Relative
Contour
Physical
model
Isobath
Perspecti
ve views
Hypsomet Relief
ric tinting shading
Which methods are combined in this map?
Absolute
Relative
Contour
Physical
model
Isobath
Perspective
views
Hypsometric
tinting
Relief
shading
Which methods are combined in this map?
Absolute
Relative
Contour
Physical
model
Isobath
Perspective
views
Hypsometric
tinting
Relief
shading
Which methods are combined in this map?
Absolute
Relative
Contour
Physical
model
Isobath
Perspective
views
Hypsometric
tinting
Relief
shading
Which methods are combined in this map?
Absolute
Relative
Contour
Physical
model
Isobath
Perspective
views
Hypsome Relief
tric tinting shading
Which methods are combined in this map?
Absolute
Relative
Contour
Physical
model
Isobath
Perspective
views
Hypsome Relief
tric tinting shading
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/
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