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Lecture 17 Terrain modelling: applications

Lecture 17 Terrain modelling: applications. Outline introduction access modelling landscape evaluation. Introduction. Many applications of terrain models visualisation covered already: hillshading and orthographic views animation and photorealism others: access modelling

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Lecture 17 Terrain modelling: applications

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

  2. 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 GEOG2750 – Earth Observation and GIS of the Physical Environment

  3. 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 GEOG2750 – Earth Observation and GIS of the Physical Environment

  4. 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 GEOG2750 – Earth Observation and GIS of the Physical Environment

  5. Example distance model output Buffer zones Distance surface Anisotropic surface Residuals GEOG2750 – Earth Observation and GIS of the Physical Environment

  6. 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 GEOG2750 – Earth Observation and GIS of the Physical Environment

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

  8. 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 GEOG2750 – Earth Observation and GIS of the Physical Environment

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

  10. 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° GEOG2750 – Earth Observation and GIS of the Physical Environment

  11. 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. GEOG2750 – Earth Observation and GIS of the Physical Environment

  12. “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 GEOG2750 – Earth Observation and GIS of the Physical Environment

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

  14. 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? GEOG2750 – Earth Observation and GIS of the Physical Environment

  15. 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 GEOG2750 – Earth Observation and GIS of the Physical Environment

  16. Calculating an inter-visibility matrix Offset a Offset b v nv v nv v nv without offset b with offset b not visible visible GEOG2750 – Earth Observation and GIS of the Physical Environment

  17. Example viewsheds GEOG2750 – Earth Observation and GIS of the Physical Environment

  18. 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 GEOG2750 – Earth Observation and GIS of the Physical Environment

  19. Wind farm impact assessment GEOG2750 – Earth Observation and GIS of the Physical Environment

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

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

  22. Visual impact of human features GEOG2750 – Earth Observation and GIS of the Physical Environment

  23. Cell phone coverage GEOG2750 – Earth Observation and GIS of the Physical Environment

  24. Military applications GEOG2750 – Earth Observation and GIS of the Physical Environment

  25. Virtual GIS GEOG2750 – Earth Observation and GIS of the Physical Environment

  26. 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. GEOG2750 – Earth Observation and GIS of the Physical Environment

  27. 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 GEOG2750 – Earth Observation and GIS of the Physical Environment

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

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

  30. Useful web links • Access modelling • http://www.geogr.ku.dk/dkgs/image/pub_pdf/artikler/2002/GT2002_05tb.pdf • Archaeology and viewshed analysis • http://www.casa.arizona.edu/MPP/viewshed/vspaper.html • Scenic highway designation • http://crssa.rutgers.edu/projects/highway/highway.html GEOG2750 – Earth Observation and GIS of the Physical Environment

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

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