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GEOG5060 GIS & Environment

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School of Geography

FACULTY OF ENVIRONMENT

GEOG5060 GIS & Environment

Dr Steve Carver

Email: [email protected]

Lecture 7: Terrain modelling â€“ geomorphometrics

- http://www.geog.leeds.ac.uk/people/a.turner/teaching/geog5060/2008/

Andy Turner

http://www.geog.leeds.ac.uk/people/a.turner/

http://www.geog.leeds.ac.uk/people/a.turner/teaching/geog5060/2008/

- Lecture
- Workshop
- Practical
- Assignment
- Assessment

Introduction

Basic metrics

Equidistant orthogonal comparisons

Other geomorphometrics

State of play

Lecture Outline

- 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

- 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

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 wonâ€™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 earthâ€™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

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

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

- Hydrological modelling 1: catchment models
- Basics of hydrology
- Creating hydrologically correct DEMs
- Modelling catchment variables