Aberdeen Institute for Coastal Science and Management, University of Aberdeen Team (alphabetical...
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Transcript of Aberdeen Institute for Coastal Science and Management, University of Aberdeen Team (alphabetical...
Aberdeen Institute for Coastal Science and Management,University of Aberdeen
Team (alphabetical order):
Alastair DawsonCristina GomezDavid GreenWilliam RitchieAmy TaylorRobert Wright
TERRAIN MODELLING FOR THE ASSESSMENT OF COASTAL CHANGE
Society of Cartographers Annual Summer Conference 2008 (1st September)
Overview
Society of Cartographers Annual Summer Conference 2008 (1st September)
• Background
• Objective
• Location of study sites
• Data used
• Methodology
• ResultsVisualization: DTM, photo mosaics
• Analysis and interpretation:Visual interpretation of geomorphologyPlanimmetric changeVolumetric change
BACKGROUND
OBJECTIVE
•Coastal environment importance: dunes and coast line.
•Lack of data of the causes and rate of change in Scotland’s natural heritage.
•Evidence of morphology change.
Study recent (last decades) changes in beach and dune systems in Scotland
Work done for the project: “Assessment of the rates and causes of change in Scotland’s beaches and dunes” (AICSM for SNH)
Society of Cartographers Annual Summer Conference 2008 (1st September)
SITES LOCATION
Selection criteria:
• Out of human excessive influence
• Areas of submergence and emergence(postglacial)
• Availability of aerial photography:
• two different dates • metric (useful for analytical
photogrammetry)
Society of Cartographers Annual Summer Conference 2008 (1st September)
DATA
Aerial photography: stereo pairs to create the DEM (Digital Elevation Model)-DTM
GCP (Ground Control Points): for photography orientation and aero triangulation
For reference and comparison:Ancillary maps: OS 1800’s coast lines for comparisonRecent maps: OS digital recent maps
Society of Cartographers Annual Summer Conference 2008 (1st September)
METHODOLOGY
Interior orientation
Import frames
Triangulation
Mosaic images DTM creation
Edition
Aerial photos
Ground Control Points Photogrammetry (Socetset)
ASCII to raster
Raster algebra Surface analysis Spatial analysis Visual analysis
Change map Contours Volume Flythrough
GIS (ArcGis)
Export to ASCII
Society of Cartographers Annual Summer Conference 2008 (1st September)
DTM creation
Overlapping60 % end lap30 % lateral
Society of Cartographers Annual Summer Conference 2008 (1st September)
Import frames: Stereo pairs
ComplexityBig areas - many stereo pairsGround Control PointsTie points
Triangulation
Society of Cartographers Annual Summer Conference 2008 (1st September)
• DTM resolution (size of raster cell)
Small enough to capture the variability of the terrain
Big areas-----big files
2-5 m
Important to compare DTMs
Finer resolution tested– disturbances, spikes
• Sources of error
PhotosGCP: 0.1 m------ but good distribution???Algorithms for triangulation and DTM creation
• Accuracy--- Better than 0.5 m
DTM creation
Product: Digital Elevation Model
Sands of Forvie 2001Sands of Forvie 1967
Results
Society of Cartographers Annual Summer Conference 2008 (1st September)
Traditional visualization of height map
Results
Society of Cartographers Annual Summer Conference 2008 (1st September)
Detail of DEM, raster Detail of DEM, contour
3D visualization of height map
DTM: Visualization
Society of Cartographers Annual Summer Conference 2008 (1st September)
Photo draped on DEM
Society of Cartographers Annual Summer Conference 2008 (1st September)
DTM: Visualization
Lucebay parallel dunes Sands of Forvie south dune in 1984 with key contour lines
Photo MosaicsVisualization
Society of Cartographers Annual Summer Conference 2008 (1st September)
Morrichmore in 2005
Analysis and interpretation
Planimmetric change: mapping and comparing lines for different dates
vegetation boundary linezero meter Above Ordnance Datum (0 m line)HWMOST (high water mark ordinal spring tide)
Volumetric change: raster algebra with pairs of DTM for comparison
Visual interpretation of DTMs geomorphology
Society of Cartographers Annual Summer Conference 2008 (1st September)
Visualization
Society of Cartographers Annual Summer Conference 2008 (1st September)
Sandwood Bay in 2004
Analysis: planimmetric change
Society of Cartographers Annual Summer Conference 2008 (1st September)
Culbin Sands
Analysis: planimmetric change
Society of Cartographers Annual Summer Conference 2008 (1st September)
Analysis: planimmetric change
Society of Cartographers Annual Summer Conference 2008 (1st September)
Society of Cartographers Annual Summer Conference 2008 (1st September)
Analysis: planimmetric change
Analysis: planimmetric changePlanimetric changes: zero m AOD line
Society of Cartographers Annual Summer Conference 2008 (1st September)
Volume change calculation: raster algebra
Analysis: volumetric change
Society of Cartographers Annual Summer Conference 2008 (1st September)
Analysis: Volumetric change
Morrichmore map of height change 1967-2005
Society of Cartographers Annual Summer Conference 2008 (1st September)
2D
3D
Visualization of volumetric changes
Society of Cartographers Annual Summer Conference 2008 (1st September)
Scheme of colours:red: erosionwhite: no changegreen: accretion
Analysis: Volumetric change
Flythroughs
Society of Cartographers Annual Summer Conference 2008 (1st September)
Location of areas with major changeEvaluation of change:
erosionaccretion
Interpretation of change, causes:climateothers
Temporal/Permanent
Analysis and Interpretation
Analysis and Interpretation
Contrast with former studies or theories
Confirmation of hypothesis
Society of Cartographers Annual Summer Conference 2008 (1st September)
Profiles for interpretation
Fo B1
-2
0
2
4
6
8
10
12
14
16
18
20
2 10 18 26 34 42 50 58 66 74 82 90 98 106
Distance (m)
Hei
gh
t (m
)
1967
2001
Fo B2
-2
0
2
4
6
8
10
12
14
16
2 10 18 26 34 42 50 58 66 74 82 90 98 106 114
Distance (m)
Hei
gh
t (m
)
1967
2001
Fo B3
-2
0
2
4
6
8
10
2 10 18 26 34 42 50 58 66 74 82 90 98 106 114
Distance (m)
Hei
gh
t (m
)
1967
2001
Society of Cartographers Annual Summer Conference 2008 (1st September)
Analysis and Interpretation
Methodology conclusions
Coastal environments present special problems in creation of DTM:
WavesPermanent water
Applicability is conditioned by:
Photography: availability, date, qualityField quality data: GCP
Sources of error: data, algorithms.
Results have to be carefully interpreted and used
Society of Cartographers Annual Summer Conference 2008 (1st September)
Main findings of the project
Scotland’s beaches and dunes are dynamic features and subject to rapid but variable rates of change. Some coastlines are advancing, some retreating.
The main factor affecting the change appears to be sediment availability and recycling.
The most recent tide data points to a typical rise in relative sea across Scotland over the last 150 years of around 30 centimeters.
The geomorphological effects on Scotland’s beaches and dunes of storminess history may be much more important but there is no firm evidence to link this to any long-term rise in relative sea level or any other aspect of climate change.
Society of Cartographers Annual Summer Conference 2008 (1st September)
Thanks for your attention
Society of Cartographers Annual Summer Conference 2008 (1st September)