Lecture 5: Terrain Analysis Department of Geography and Urban Studies, Temple University GUS 0265/0465 Applications in GIS/Geographic Data Analysis Lecture 5: Terrain Analysis

Terrain Operations slope aspect (orientation) hillshade intervisibility

Digital Elevation Model (DEM) 3 3 3 3 4 3 3 3 4 4 3 3 4 4 4 4 4 4 5 5 4 4 5 5 5

Percent Slope Calculation % slopee = where a b c d e f g h i

% slopee = 7 5 3 e 2 1 = (7 + 2(5) + 2) – (3 + 2(2) +1) = 11 10 m resolution 7 5 3 e 2 1 = (7 + 2(5) + 2) – (3 + 2(2) +1) = 11 = (7 + 2(5) + 3) – (2 + 2(1) +1) = 15 a b c d e f g h i = 80 = 80

% slopee = 10 m res = 7 5 3 e 2 1 = a b c d e f g h i ~0.23 =

Aspect (orientation)

Aspect (orientation)

Hillshade

Intervisibility

Intervisibility observer DEM Visibility 1 Elevation in meters 32 35 34 42 47 43 33 44 53 52 46 39 55 56 45 54 32 35 34 42 47 43 33 44 53 52 46 39 55 56 45 54 1 Elevation in meters resolution = 100 meters Is there a higher elevation between observer and each cell? 0 not visible 1 visible

Hydrologic Modeling Fill Sinks Flow Direction Flow Accumulation Eliminate ‘pits’ in the DEM Flow Direction cell value indicates the direction of flow from a given cell Flow Accumulation cell value indicates the number of cells flowing into a given cell Stream Delineation cell value indicates whether a cell is a stream Watershed Delineation cell value indicates whether a cell is within an upslope contributing area of a given cell

Fill Sinks

Flow Direction

Flow Accumulation

Stream Delineation Selects cells above a certain threshold flow accumulation value

Basin Delineation

Watershed Delineation