1. GEOG Mid term

3. Digital Elevation Models (DEM) - Terrain Models (DTM)
A DEM is a continuous grid of elevation values - one height per pixel (grid cell)
They are the modern equivalent of terrain previously stored in contour lines

4. Google Earth – 3D perspectives (and flythroughs)

5. DEM creation by digitising contours (e.g. NTS maps -> NTDB layer).
This is 'second hand' digital, as contours are abstract
stereo photos -> contour lines -> digitised lines -> convert to raster GRID (topo to raster)

6. DEM Grid

7. 2. Digital stereo-photogrammetry: (e.g. BC TRIM)
This is a better option, captured directly from aerial photographs
stereo photos -> mass points -> convert to raster GRID (topo to raster)

8. Traditional method : stereo photos –> contours -> shaded relief Digital method: digital photos –> points –> DEM –> shaded relief and DEM <-> Contours Air Photo DEM Shaded relief
This is the DEM – for data analysis

9. Ikonos 5m 3. Direct image grid DEM (> year 2000)
Stereo digital satellite raster imagery
Ikonos 5m

10. SRTM    (Shuttle Radar Topographic Mission): 90 metre pixels, 56ºS-60ºN

11. DEM sources: global GTOPO30 ~1993 1km

12. LiDAR DEM

13. TYPICAL RESOLUTION (metres)
DEM data
DEMs have been created at a variety of scales by different agencies. Some can be downloaded free – all except the top one in this list
AGENCY 
SCALE 
TYPICAL RESOLUTION (metres)
B. Municipal 
1: 5,000  1 
B. Provincial 
1: 20,000 
25 
A. Federal 
1: 50,000  50
1: 250,000 
200 
A. Global 
1: 1,000,000   
e.g City of PG
BC TRIM
->
CDED:
Canadian Digital Elevation Data
C. Global-SRTM 1: 100,

14. How have DEMs impacted relief depiction ?
Sugar-loafs and hachures – added graphically (not a software option)
Contours
Hypsometric Tints
Shaded relief (hillshading)
Tanaka illuminated contours
Slope zones
3D perspectives
Fly throughs
True 3D

15. Contour lines can be interpolated from DEM heights or pre-exist from digitised maps, and are a standard layer in digital databases and online web mapping for display.

16. Hypsometric Tints Selection of hues, chromas from colour sequences
<- legend labels

17. Shaded relief (hillshading)
Addition of shading from an imaginary Northwest Light source

18. Shaded relief (hillshading) : No longer does the practitioner require artistic ability.
The user selects azimuth and zenith, 315 and 45 standard to match the NW light source.
It is easily generated but may not be as good as from a skilled artist

19. Using the transparency option for shading and tints

20. JLC Geomatique – addition of shaded relief to topographic maps
For BC TRIM maps, see:

21. Tanaka relief contours – not a common software option

22. Tanaka Contours – Forests for the World (by applying hillshading to contours)

23. Slope and aspect layers (GIS analysis)

24. 3D perspectives: Rocky Mountain trench – Castle Creek Glacier

25. Trails – UNBC to Peden Hill Dan Abraham, 2005

26. 3D perspectives
Perspectives are produced by GIS and visualization software. The user selects parameters such as viewing angle, vertical exaggeration and what may overlay the terrain, such as a 'draped' aerial photograph, scanned map or map layers.

27. Whistler – Brandywine Meadows

28. Whistler – Brandywine Meadows (terrain + shaded relief)

29. Four DEMs (North Vancouver): 1km (GTOPO30), SRTM (90m); CDED 1:250,000 (100m); CDED 1:50,000 (25m) CDED = Canadian Digital Elevation Data

30. Four DEMs (North Vancouver): 1km (GTOPO30), SRTM (90m); CDED 1:250,000 (100m); CDED 1:50,000 (25m)
Pick your own map sheet in Lab 7 / assignment #2

31. Physical Models: Challenger map (1947-54) 25 x 25 m ~1:50,000

32. True 3D physical models http://www.stm-usa.com/bc.htm
(40 x 74 feet 1:99,000)