Stream Network Flashcards
Surface
geographic phenomenon represented as a set ofcontinuous data, such as elevation or airtemperature over an area. Surfaces can berepresented by models built from regularly orirregularly spaced sample points on the surface.
Surface model
Digital abstraction or approximation of a surface.Because a surface contains an infinite number ofpoints, some subset of points must be used torepresent the surface. Each model contains aformalized data structure, rules, and X,Y,Z point measurements that can be used to represent asurface
Elevation and slope
change across the landscape (Figure11-1) , and this variation determines where rivers flow,lakes occur, and floods arefrequent
Laser Detection And Ranging
a surveying method that measures distance to a target by illuminating thetarget with pulsed laser light and measuring the reflected pulses with a sensor. Differences in laser return times and wavelengths can then be used tomake digital 3D representations of the target
Digital elevation models (DEMs)
are one of many products that can be derived fromlidar data, though they can also be derived from other sources. DEMs are digitalrepresentations of the earth’s topographic surface. They’re a “bare-earth” product because they do not include surface features like buildings and vegetation
Slope
defined as the change in elevation (a rise) with a change in horizontal position (a run), reported in degrees, between zero (flat), and 90 (vertical)
Slope tool
identifies the steepness at each cell of a rasters surface. The lower the slope value,the flatter the terrain; the higher the slope value, the steeper the terrain.
Aspect tool
identifies the direction the downhill slope faces. The values of each cell in the output raster indicate the compass direction the surface faces at that location. It is measured clockwise in degrees from 0 (due north) to 360 (again due north), coming full circle. Flat areashaving no downslope direction aregiven a value of -1
