GEOG5060 GIS

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GEOG5060 GIS Environment
School of Geography FACULTY OF ENVIRONMENT

• Dr Steve Carver
• Email S.J.Carver_at_leeds.ac.uk

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Lecture 7 Terrain modelling geomorphometrics

• http//www.geog.leeds.ac.uk/people/a.turner/teachi
  ng/geog5060/2008/

• Andy Turner
• http//www.geog.leeds.ac.uk/people/a.turner/
• A.G.D.Turner_at_leeds.ac.uk
• http//www.geog.leeds.ac.uk/people/a.turner/teachi
  ng/geog5060/2008/

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Course Component

• Lecture
• Workshop
• Practical
• Assignment
• Assessment

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Lecture Outline

• Introduction
• Basic metrics
• Equidistant orthogonal comparisons
• Other geomorphometrics
• State of play

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Assignment

• This part of the course is about working together
  to improve our teaching and research on
  geomorphometrics
• During the lecture consider areas in which you
  could address some of the gaps I will mention
• I am asking you to contribute and develop this
  part of the course
• Your contribution really could be anything!
• I am also keen for you to collaborate and work
  together in groups or en masse

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Some assignment ideas

• Update wikipedia or other encyclopedia type web
  content
• http//www.wikinfo.org/index.php/Geomorphometrics
• http//www.wikipedia.org/wiki/Geomorphometrics
• Improve course materials
• Contribute a research article based on applied or
  investigative work
• Develop software
• Results visualiser
• Graphical User Interface

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Definition

• Geomorphometrics are measures of the state and
  change in surface geometry of geophysical
  horizons. They are topographic measures that can
  be used in terrain analysis and geographical
  modelling.
• http//www.geog.leeds.ac.uk/people/a.turner/resear
  ch/interests/geomorphometrics/

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Apologies and acknowledgement

• Last night I spent hours developing these lecture
  slides only to lose most of the work
• I am probably more annoyed by this than you will
  be
• Hopefully you wont suffer as much as me as a
  consequence
• What follows are some slides developed by some in
  the class of 2007 with a new template applied and
  jiggled around a bit so you can see all the
  various images and text.

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Last 2 Lectures

• Terrain analysis 1
• DEMs and DTMs
• derived variables
• example applications
• Terrain analysis 2
• access modelling
• landscape evaluation
• hazard mapping

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Origins

• Peter Fisher
• Peakiness
• Development of a grids package
• The SPIN!-project
• MedAction, DesertLinks and tempQsim
• Desire for greater flexibility, capability and
  freedom than that offered by commercial
  proprietary GIS

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Overview

• So what are geomorphometrics?
• Measures of the relative heights of the land of
  the earths surface to allow comparison of
• Topography
• Terrain analysis e.g. how peaky is an area?
• Surface geometry of the earth.

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Raster Elevation Data

• DEM data interpolated from vector data
• Widely available for many planets and regions of
  Earth
• SRTM 3 arc secs
• Publicly available
• OS 10 metre
• Available via chest
• LIDAR 2 meter
• Available but unlicensed
• Getting better all the time
• Uncertainties abound

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Example DEM
Red areas indicate high altitude, green low
altitude
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Future DEMs

• Higher spatial resolution
• Larger regions
• More values
• Larger ranges
• More detailed precision
• 3D spatial
• Temporal change
• Hundreds of thousands of millions of data points

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Data pre-processing

• One of the first things to do is to be able to
  process all this data
• Grids 1.0 beta
• Clean the data
• Mask
• Are there any holes?
• How can we cope best with these

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Data pre-processing continued...

• Define the river basins, catchments and HRUs for
  the DEM
• Develop land degradation risk indicators
• Erosion
• Salinity
• Develop a fully distributed hydrological model

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Recap

• Geomorphometrics compare relative heights of
  cells
• Allowing comparison of terrain, topology
• Uncertainty is always present

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Basic metrics
Slopeyness
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Question

• Can any one suggest the name of another basic
  geomorphometric?

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Slope and Aspect

• Slope is the gradient of an area
• http//en.wikipedia.org/wiki/Slope
• and aspect is the angle to a particular
  orientation over a given region
• http//en.wikipedia.org/wiki/Aspect_28geography2
  9

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Other metrics

• Slopyness
• Upness
• Downess
• Flatness
• Roughness

Flatness calculated for the 2 cell neighbourhood
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What region? How to calculate it?

• Circular region using equidistant orthoganal
  comparisons
• Vector addition
• Distance weighting
• Scale
• NB From the model output white regions indicate
  areas of high values for that metric

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Slope 13 cell neighbourhood
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Slope 49 cell neighbourhood
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Slope 8
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Aspect 2
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Aspect 4
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Aspect 8
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Scale and distance weighting

• Distance weighting
• Differencing to focus on nid-scales can be done
  directly by applying a more complex spatial
  weighting scheme
• Only relevant for some measures
• Not aspect
• What about upness and downness?

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Equidistant orthogonal comparisons

• Rotation invariant metrics

• For each metric, compare each orthoganal set
  within a region
• What is observed?
• hhhh, hhhl, hhll, llhl hlll, llll

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• Axis based metrics

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HLHL / LHLH
HHLL / LHHL / HLLH

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HHHL - saddle
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HHHH - crater
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Geog 5060 GIS Environment Lecture 7
HHLL - slope
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LLLL - peak
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Considerations

• How to treat cells with the same height?
• How to treat cells with no data value?
• What conditioners are appropriate?
• Two types of weight
• Distance weighting
• Difference in elevation weighting
• What is best?

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Example 1w_hhll
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Example 4sumd_abs_xlxh_ai_lllh
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Axis based metrics

• Profile or Contour
• Concavity or Convexity
• Convergence or Divergence

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Considerations

• What other interesting metrics?
• minimum type profile concavity
• maximum type profile convexity
• Better for identifying features?
• Probably best in combination with the other
  metrics
• Sorry, no examples!

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Other geomorphometrics

• Up and down slope type geomorphometrics
• Upslope area
• Complex distance weighting
• More hydrological type metrics
• Flow accumulation
• Visibility based metrics
• Monte Carlo type uncertainty of all

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Software

• Proprietary or closed source
• Commercial
• Research
• LandSerf
• TauDEM
• Open source
• GMT
• Grids

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Summary

• Basic metrics
• Equidistant orthogonal comparisons
• Scale and distance weighting
• Rotation invariant metrics
• Scale and distance weighting - uncertainty

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Next Steps

• Practical
• Experiment with a program to generate
  geomorphometrics in teams
• Friday 1200 to 1600 in Masters computing room,
  Geography East Building.
• Develop an output of some sort and explain the
  processes you went through to produce it.
• Assignment
• Show understanding of geomorphometrics and
  develop the subject

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Next week

• Hydrological modelling 1 catchment models
• Basics of hydrology
• Creating hydrologically correct DEMs
• Modelling catchment variables
• Workshop Catchment modelling in GRID
• Practical Catchment modelling