GEOG5060 GIS & Environment Lecture 7 GEOG5060 - GIS and Environment1 Lecture 7. Terrain analysis 3:...

Lecture 7 GEOG5060 - GIS and Environment 1

GEOG5060GIS &

EnvironmentLecture 7

Lecture 7.Terrain analysis 3: geomatics;

geomorphometrics

Andy Turner


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Course component

• Lecture

• Workshop

• Practical

• Assignment

• Assessment


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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 adress some of the gaps I will mention – it really could be anything!


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Definitions

• Geomatics– Geomatics is a modern discipline, which integrates

acquisition, modelling, analysis, and management of spatially referenced data, i.e. data identified according to their locations

http://en.wikipedia.org/wiki/Geomatics

• Geomorphometrics– Geomorphometrics are measures of the state and change in

surface geometry of the Earth's physical 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/


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Idea for assignment

• Develop wikipedia pages on geomorphometrics and link it to the geomatics wikipedia page– What other things are related?

• Hydrology– Hydroinformatics– Surface water hydrology

• Landform identification• Geomorphology

- What combination of metrics can be used to identify different landforms?– What other than the standard offering would be useful?– You can even base your project on previous years work –

ask me


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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

height

slopeaspect

hillshading

plan curvature FeatureFeature

extractionextraction


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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 earth’s 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 based

• Raster Elevation Data– DEM data interpolated from vector data– Widely available– 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

• SRTM DEM data is being produced at a 1 arc second resolution– America is available

• Soon after we will have higher resolution…• We have 10 meter resolution DEM for the UK…

– Again hundreds of thousands of rows and columns– How was it produced?– Is it any good?

• Soon we will have more higher spatial resolution


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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 contd.

• 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

Slopyness and Levelness calculated for the 2 cell neighborhood


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Question

• Can any one suggest the name of a 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_%28geography%29


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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

B4

A4

E3

D4

C4

D3

B3

E4

A3 E2

C3

*

C1

A1 B1

D1

C2

D2

E1

A2

B2 . A .

. B C B .

A C X C A

. B C B .

. A .

•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

B4

A4

E3

D4

C4

D3

B3

E4

A3 E2

C3

*

C1

A1 B1

D1

C2

D2

E1

A2

B2


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H

L r H

L

H

L r L

H

HHLL / LHHL / HLLH

HLHL / LHLH


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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 1:w_hhll


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Example 4:sumd_abs_xlxh_ai_lllh


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Axis based metrics

• Profile or Contour

• Concavity or Convexity

• Convergence or Divergence

B4

A4

E3

D4

C4

D3

B3

E4

A3 E2

C3

*

C1

A1 B1

D1

C2

D2

E1

A2

B2


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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 used

• Proprietary or closed source– Commercial– Research

• LandSerf• TauDEM

• Open source– GMT– Grids


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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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Other geomorphometrics

• Up & down slope type geomorphometrics– Upslope area

• Complex distance weighting

– More hydrological type metrics• Flow accumulation

• Visibility based metrics• Time and dynamics• Sensitivity & Monte Carlo type uncertainty

of all


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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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Assignment

• Show understanding of geomorphometrics

• Experiment with the program in teams. Friday 2-4.

• Develop an output of some sort and explain the processes you went through to produce it.


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Next week…

• Hydrological Modelling 1:– Catchment Models– With Katherine Arrell

GEOG5060 GIS & Environment Lecture 7 GEOG5060 - GIS and Environment1 Lecture 7. Terrain analysis 3:...

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