1. Week 21GEOG2750 – Earth Observation and GIS of the Physical Environment1 Lecture 17 Terrain modelling: applications Outline – introduction – access modelling – landscape evaluation

2. Week 21GEOG2750 – Earth Observation and GIS of the Physical Environment2 Introduction Many applications of terrain models –visualisation covered already:  hillshading and orthographic views  animation and photorealism –others:  access modelling  visibility analysis and landscape evaluation  slope and hazard mapping  hydrological modelling

3. Week 21GEOG2750 – Earth Observation and GIS of the Physical Environment3 Access modelling Terrain is a vital element for realistic access models –flat, boundless plains of Weberian industrial location analysis just don’t exist! –need to take terrain-based costs into account  Slope as push/pull factor  Barrier features –additional layer in GIS access models

4. Week 21GEOG2750 – Earth Observation and GIS of the Physical Environment4 Distance models Isotropic distance models –don’t take cost factors into account –e.g. eucdistance in GRID or buffer in Arc/Info Anisotropic distance models –take cost factors into account –e.g. costdistance in GRID

5. Week 21GEOG2750 – Earth Observation and GIS of the Physical Environment5 Example distance model output Buffer zonesDistance surface Anisotropic surfaceResiduals

6. Week 21GEOG2750 – Earth Observation and GIS of the Physical Environment6 Routing models Cost or “friction” surfaces can be used to calculate shortest path between two points –Euclidean model takes only distance into account  result is straight line or “as the crow flies” –anisotropic model takes cost or friction surface into account  may be positive (push) or negative (pull)  uses “cost” of traversing a cell in a particular direction to identify least accumulative cost route  result is unlikely to be a straight line

7. Week 21GEOG2750 – Earth Observation and GIS of the Physical Environment7 Example routing output Actual route Predicted route Minimum distance/time surface Crianlarich-Benmore circular walk Check- points

8. Week 21GEOG2750 – Earth Observation and GIS of the Physical Environment8 Case study: modelling remoteness Off-road accessibility is function of: –distance from nearest road –slope relative to direction of travel –ground conditions (trafficability) –barrier features (rivers, lakes, cliffs, etc.) Combine within anisotropic access model as cost or friction surfaces

9. Week 21GEOG2750 – Earth Observation and GIS of the Physical Environment9 Question What other cost factors might we include in a model of off-road accessibility?

10. Week 21GEOG2750 – Earth Observation and GIS of the Physical Environment10 Remoteness model Combined model integrating: –Dijkstra’s Shortest Path Algorithm  calculate shortest path from origin to any destination based on relative costs of movement through set of cells between origin and destination –Naismith’s Rule (1892)  “an hour for every three miles on the map, with an additional hour for every 2,000 feet of ascent”  -10 minutes/300 m descent for slopes 5°>12°; +10 minutes/300 m descent for slopes >12°

11. Week 21GEOG2750 – Earth Observation and GIS of the Physical Environment11 Results Naismith's/Dijkstra's model used to model relative remoteness of Cairngorms area under different scenarios –with and without mountain-bike access along trails –before and after proposed ski funicular ArcGIS alternative Costpath –calculates the least-accumulative-cost distance over cost surface from source cell(s) accounting for surface distance and horizontal/vertical cost factors.

12. Week 21GEOG2750 – Earth Observation and GIS of the Physical Environment12 “What if?” modelling of Mountain bike restrictions Mar Lodge estate With mountain bike use along track from Linn of Dee Without mountain bike use along track from Linn of Dee

13. Week 21GEOG2750 – Earth Observation and GIS of the Physical Environment13 Effects of the Cairngorm Ski Funicular Without parking restrictions at the Day Lodge or along access road With parking restrictions at the Day Lodge and along access road

14. Week 21GEOG2750 – Earth Observation and GIS of the Physical Environment14 Visibility analysis Use of DTM to calculate “viewshed” of particular point –where can point X be seen from on surface Y? –what part of surface Y can be seen from point X? Multiple point viewsheds combined to calculate viewshed of line and area features –where and part of feature X be seen on surface Y? –what part of surface Y can be seen from which point on feature X?

15. Week 21GEOG2750 – Earth Observation and GIS of the Physical Environment15 Calculating viewsheds Uses line of sight from observer point to terrain surface to calculate intervisibility matrix: –visible parts of terrain surface –non-visible areas (i.e. ‘dead’ areas) Use of observation point and terrain offsets –e.g. height of person or observation tower –e.g. height of wind turbine or other feature

16. Week 21GEOG2750 – Earth Observation and GIS of the Physical Environment16 Calculating an inter-visibility matrix Offset b Offset a vvvnv visible not visible without offset b with offset b

17. Week 21GEOG2750 – Earth Observation and GIS of the Physical Environment17 Example viewsheds

18. Week 21GEOG2750 – Earth Observation and GIS of the Physical Environment18 Uses of visibility analysis Many different uses… –visual impact analysis –landscape evaluation –siting of observation towers and cellular communications masts –modelling coverage of cellular communications –military applications –virtual GIS

19. Week 21GEOG2750 – Earth Observation and GIS of the Physical Environment19 Wind farm impact assessment

20. Week 21GEOG2750 – Earth Observation and GIS of the Physical Environment20 Landscape evaluation of Scotland Litton’s 1968 scenic assessment 50m DEM Intervisibility matrix (After Miller)

21. Week 21GEOG2750 – Earth Observation and GIS of the Physical Environment21 Landscape evaluation of Britain

22. Week 21GEOG2750 – Earth Observation and GIS of the Physical Environment22 Visual impact of human features

23. Week 21GEOG2750 – Earth Observation and GIS of the Physical Environment23 Cell phone coverage

24. Week 21GEOG2750 – Earth Observation and GIS of the Physical Environment24 Military applications

25. Week 21GEOG2750 – Earth Observation and GIS of the Physical Environment25 Virtual GIS

26. Week 21GEOG2750 – Earth Observation and GIS of the Physical Environment26 Conclusions Many uses for DEMs in environmental applications of GIS –key variable determining accessibility –important landscape variable –controlling factor in “gravity” hazards including flooding, avalanches, landslides, etc.

27. Week 21GEOG2750 – Earth Observation and GIS of the Physical Environment27 Practical Visibility assessment Task: Calculate viewshed of a wind farm Data: The following datasets are provided… –Digital elevation model (50m resolution 1:50,000 OS Panorama data) –Wind farm turbine location(s) –ITE LCM90 data

28. Week 21GEOG2750 – Earth Observation and GIS of the Physical Environment28 Practical Steps: 1.Display DEM and turbine locations in ArcMap or GRID 2.Calculate viewshed of wind turbines using both 1 and 16 turbines assuming a turbine height of 30m using visibility 3.Display results in ArcMap or GRID

29. Week 21GEOG2750 – Earth Observation and GIS of the Physical Environment29 Learning outcomes Familiarity with the VISIBILITY command in Arc/Info Experience with developing impact assessments based on environmental variables

30. Week 21GEOG2750 – Earth Observation and GIS of the Physical Environment30 Useful web links Access modelling –http://www.geogr.ku.dk/dkgs/image/pub_pdf/artikler/2 002/GT2002_05tb.pdfhttp://www.geogr.ku.dk/dkgs/image/pub_pdf/artikler/2 002/GT2002_05tb.pdf Archaeology and viewshed analysis –http://www.casa.arizona.edu/MPP/viewshed/vspaper.ht mlhttp://www.casa.arizona.edu/MPP/viewshed/vspaper.ht ml Scenic highway designation –http://crssa.rutgers.edu/projects/highway/highway.htmlhttp://crssa.rutgers.edu/projects/highway/highway.html

31. Week 21GEOG2750 – Earth Observation and GIS of the Physical Environment31 Next week… Hydrological modelling –Basics of hydrology –Creating hydrologically correct DEMs –Modelling catchment variables Practical: –Derive stream network from DEM