terrain mapping dems contours slope aspect hillshades
TRANSCRIPT
Terrain Mapping
• DEMs
• Contours
• Slope
• Aspect
• Hillshades
200 Meter Countours
Calculating SlopeDEM Cross Section
Slope Calculation
• Fits a plane through 3x3 pixels around the pixel of interest
• What effect does this have on the uncertainty of the resulting raster?
108 109 113
112 123 128
125 127 130
Slope Calculation
Angle
Rise
Run
Slope = (Rise/Run) * 100%
Can be:-Degrees-Percent
3 x 3 Cell
Angle
Z-Factor
• Converts the elevations in the DEM to the same units as the x,y dimensions
• Easiest approach is to:– Project the DEM to a spatial reference that
is in meters (i.e. UTM)– Scale the elevation values the meters if not
already in meters
Aspect – Direction of the slope
Slope
Aspect (Direction)
Angle
Rise
Run
Slope = (Rise/Run) * 100%
Hillshade
• Creates a raster that appears to be a photo from above the area, shaded by the sun.
• Frequently used as a background, rarely for analysis
• Z-factor can be used to make the hillshade more dramatic
Hill-shade
Hillshade: Z-Factor=1
Hill-shade: Z-Factor=10
Hillshade: RMNP
Resample Can Remove Artifacts
Resolution*2, Bicubic
Create Your Own Backgrounds!