terrain mapping dems contours slope aspect hillshades

Terrain Mapping

• DEMs

• Contours

• Slope

• Aspect

• Hillshades

Digital Elevation Model (DEM)

Mt. Hood

Counters

• Generates a polyline Shapefile

Contours

DEM Cross Section

2000m

1900m

2100m

2200m

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

Slope

Aspect – Direction of the slope

Slope

Aspect (Direction)

Angle

Rise

Run

Slope = (Rise/Run) * 100%

Aspect

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

Color Hillshade

• Transparent DEM with Color Ramp

Hillshade: RMNP

Resample Can Remove Artifacts

Resolution*2, Bicubic

Create Your Own Backgrounds!