School of Geography FACULTY OF ENVIRONMENT. GEOG5060 GIS & Environment. Dr Steve Carver Email: [email protected] Lecture 7: Terrain modelling – geomorphometrics. http://www.geog.leeds.ac.uk/people/a.turner/teaching/geog5060/2008/. Andy Turner
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School of Geography
FACULTY OF ENVIRONMENT
GEOG5060 GIS & Environment
Dr Steve Carver
Email: [email protected]
Lecture 7: Terrain modelling – geomorphometrics
Andy Turner
http://www.geog.leeds.ac.uk/people/a.turner/
http://www.geog.leeds.ac.uk/people/a.turner/teaching/geog5060/2008/
Introduction
Basic metrics
Equidistant orthogonal comparisons
Other geomorphometrics
State of play
Lecture Outline
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/research/interests/geomorphometrics/
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 won’t 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.
Terrain analysis 1
DEMs and DTMs
derived variables
example applications
Terrain analysis 2
access modelling
landscape evaluation
hazard mapping
height
aspect
slope
hillshading
plan curvature
Featureextraction
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
So what are geomorphometrics?
Measures of the relative heights of the land of the earth’s surface to allow comparison of:
Topography
Terrain analysis e.g. how peaky is an area?
Surface geometry of the earth.
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
Red areas indicate high altitude, green low altitude
Higher spatial resolution
Larger regions
More values
Larger ranges
More detailed precision
3D spatial
Temporal change
Hundreds of thousands of millions of data points
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
Define the river basins, catchments and HRUs for the DEM
Develop land degradation risk indicators
Erosion
Salinity
Develop a fully distributed hydrological model
Geomorphometrics compare relative heights of cells
Allowing comparison of terrain, topology
Uncertainty is always present
Slopeyness
Can any one suggest the name of another basic geomorphometric?
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_%28geography%29
Slopyness
Upness
Downess
Flatness
Roughness
Flatness calculated for the 2 cell neighbourhood
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
Slope 8
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?
Rotation invariant metrics
E4
A1
B1
B4
D4
C1
D1
E1
A4
C4
*
C2
A2
E3
D3
C3
D2
B2
B3
A3
E2
Axis based metrics
E4
A1
B1
B4
D4
C1
D1
E1
A4
C4
*
C2
A2
E3
D3
C3
D2
B2
B3
A3
E2
HLHL / LHLH
HHLL / LHHL / HLLH
HHHL - saddle
HHHH - crater
Geog 5060 GIS & Environment Lecture 7
HHLL - slope
LLLL - peak
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?
Profile or Contour
Concavity or Convexity
Convergence or Divergence
E4
A1
B1
B4
D4
C1
D1
E1
A4
C4
*
C2
A2
E3
D3
C3
D2
B2
B3
A3
E2
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!
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
Proprietary or closed source
Commercial
Research
LandSerf
TauDEM
Open source
GMT
Grids
Basic metrics
Equidistant orthogonal comparisons
Scale and distance weighting
Rotation invariant metrics
Scale and distance weighting - uncertainty
Summary
Practical
Experiment with a program to generate geomorphometrics in teams
Friday 12:00 to 16:00 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
Next Steps