1. 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

2. Terrain Operations slope aspect (orientation) hillshade
intervisibility

3. 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

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

5. % 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

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

7. Aspect (orientation)

8. Aspect (orientation)

9. Hillshade

10. Intervisibility

11. Intervisibility observer DEM Visibility 1 Elevation in meters32 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

12. 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

13. Fill Sinks

14. Flow Direction

15. Flow Accumulation

16. Stream Delineation
Selects cells above a certain threshold flow accumulation value

17. Basin Delineation

18. Watershed Delineation