Chapter 11 - Terrain Analyses Flashcards
This describes the vertical and horizontal dimensions of a land surface
Terrain
What is another name for terrain?
Land relief
This is “land relief” or terrain for underwater surfaces
Bathymetry
What are at least three of five processes that are impacted by terrain?
- Hydrology; 2. Soils/erosion; 3. Weather/climate; 4. Construction; 5. Military operations
This terrain variable describes elevation above datum
Height
This terrain variable describes rise over run
Slope
This terrain variable describes the direction of slope
Aspect
This terrain variable describes the watershed above a point
Upslope area
This terrain variable describes the longest path to a point
Flow length
This terrain variable describes terrain curvature
Profile curvature
This terrain variable describes site obstruction
Visibility
Is terrain analysis well-established in GIS?
Yes
Do many data and analytical methods exist for terrain analysis in GIS?
Yes
Are terrain analysis calculations difficult to program?
No
Are terrain analysis results shown to be inaccurate?
No
Is elevation data available for most surfaces?
Yes
Are elevation data sets frequently updated?
Yes
Is terrain analysis data cheap to collect?
No
What are three ways terrain can be modeled in GIS?
Raster, vector, TIN
What is the most commonly used data type for terrain analysis?
Raster
What are two reasons why raster is the most commonly used method for terrain analysis?
Simple structure and clear-cut math operations
Raster terrain analysis uses this approach
Moving window
Different these are used for different calculations in moving window raster terrain analysis
Kernels
These are connected lines of equal elevation
Contour lines
What is another name for contour lines?
Isoclines
Contour lines represent elevation at these
Fixed intervals
This aspect of contour lines varies among maps and scales
Interval
Contour lines run this way to slope
Perpendicular
This aspect of contour lines portrays terrain shape
Shape and density of lines
Contour lines are an old method of symbolizing terrain on these
Maps
Contour lines are a feature of these maps
USGS 7.5’ + 15’ quads
What are two ways of creating contour line maps?
- Stereo aerial photos; 2. Grid of sampled elevation points
This describes the shape of a landscape
Terrain morphology
Terrain morphology affects the direction and rate of movement of these
Surface processes
What are at least three of four common measures of terrain morphology?
- Slope; 2. Aspect; 3. Plan curvature; 4. Profile curvature
This is the change in elevation over distance, or the tilt of land
Slope
Slope is measured along the path of this
Steepest vertical change
What are the three ways to express slope?
- Degree slope; 2. Percent slope; 3. Ratio
This expresses slope as an angle
Degree slope
This expresses slope as rise over run
Percent slope
This expresses slope as a vertical distance over a horizontal distance
Ratio
Calculating slope with raster data must integrate these two things
Elevation change in X direction and elevation change in Y direction
Do slopes usually pass through cell centers?
No
This describes the cardinal direction of a slope
Aspect
Aspect is reported as this
Azimuth (0-360 degrees)
Aspect is calculated based on this
dZ/dx + dZ/dy
This describes concave and convex terrain
Curvature
Curvature is a complex calculation using these for a 9-cell neighbor
Elevation values
What are the two types of curvature?
Plan and profile curvature
What are three types of morphometric features?
Pits, peaks, saddles
These maps show concavities and convexities
Morphometric maps
DEM data is used extensively for the study of this
Hydrology
This quantifies direction of overland or subsurface flow
Flow direction
What are two ways to express direction of flow?
- Compass heading (0-360 degrees); 2. Cell ID that flow moves toward
Flow direction can be calculated using aspect and other elevation measures among these
Adjacent cells
These cause problems in hydrological analysis and must be identified and filled
Spurious ‘pits’
This is an area that supplies flow through a point on a landscape
Watershed
What are three other terms for watershed?
Basin, catchment, drainage
This is used to find watershed boundaries
Flow direction
These define areas with likely surface water
Drainage networks
These identify flow divergent and convergent zones
Wetness indices
What are three things that wetness indices can predict?
Soil moisture, flooding, plant communities
This describes the surface area visible from a point
Viewshed
What are at least two of three uses of viewsheds?
- Locating roads/factories/utilities; 2. Managing scenic areas; 3. Military field operations
Viewsheds are calculated using this
Cell-to-cell visibility
In viewshed analysis, lines of sight are drawn between these
View cells and target cells
These depict terrain as landscapes of light and shadow
Shaded relief maps
What is another term for shaded relief maps?
Hillshade maps
How are shaded relief maps produced?
By calculating surface brightness of each cell
What are two things that shaded relief maps depend on?
Terrain and sun position
When are shaded relief map cells brightest?
When angle = 90 degrees