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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

Lecture 17Terrain modelling: applications

Outline

introduction

access modelling

landscape evaluation

GEOG2750 – Earth Observation and GIS of the Physical Environment

introduction
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

access modelling
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

distance models
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

example distance model output
Example distance model output

Buffer zones

Distance surface

Anisotropic surface

Residuals

GEOG2750 – Earth Observation and GIS of the Physical Environment

routing models
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

example routing output
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

case study modelling remoteness
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

question
Question
  • What other cost factors might we include in a model of off-road accessibility?

GEOG2750 – Earth Observation and GIS of the Physical Environment

remoteness model
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

results
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

what if modelling of mountain bike restrictions mar lodge estate
“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

effects of the cairngorm ski funicular
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

visibility analysis
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

calculating viewsheds
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

slide16

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

example viewsheds
Example viewsheds

GEOG2750 – Earth Observation and GIS of the Physical Environment

uses of visibility analysis
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

wind farm impact assessment
Wind farm impact assessment

GEOG2750 – Earth Observation and GIS of the Physical Environment

landscape evaluation of scotland
Landscape evaluation of Scotland

Intervisibility matrix

(After Miller)

50m DEM

Litton’s 1968 scenic assessment

GEOG2750 – Earth Observation and GIS of the Physical Environment

landscape evaluation of britain
Landscape evaluation of Britain

GEOG2750 – Earth Observation and GIS of the Physical Environment

visual impact of human features
Visual impact of human features

GEOG2750 – Earth Observation and GIS of the Physical Environment

cell phone coverage
Cell phone coverage

GEOG2750 – Earth Observation and GIS of the Physical Environment

military applications
Military applications

GEOG2750 – Earth Observation and GIS of the Physical Environment

virtual gis
Virtual GIS

GEOG2750 – Earth Observation and GIS of the Physical Environment

conclusions
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

practical
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

practical28
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

learning outcomes
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

useful web links
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

next week
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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