Capturing & working with 3D data in heritage contexts

Wessex Archaeology

Capturing & working with 3D
data in heritage contexts

A view from the coalface

Paul Cripps
•Geomatics Manager, Wessex Archaeology
•Archaeological Computing Research Group, University of Southampton

http://www.wessexarch.co.uk/geomatics Computer Applications & Quantitative Methods in Archaeology. Southampton. March 2012.

Wessex Archaeology

Overview

• Toolbox
– Laser scanners
– GNSS
– Photogrammetry
– Aerial systems
• How?
– How do we use the tools
available?
– Advantages/disadvantages
– Workflows
• Case studies


Wessex Archaeology

The toolbox approach

• Many tools/techniques now available
• Each have strengths/weaknesses
• Need to apply right tools for the job in hand
• Right people for the job:
– Survey specialists may not fully appreciated needs of
heritage projects
– Heritage specialists may not fully appreciate survey
techniques
– Team effort!


Wessex Archaeology

Laser Scanning

• Terrestrial Laser Scanners (TLS), Close Range Laser
Scanners, Airborne Laser Scanners (ALS) provide
additional survey/recording tools
– Not universal panacea
– Ideal for capturing large amounts of 3D surface measurements
– Part of an armoury which includes traditional measured drawing,
photogrammetry, (rectified) photography, TST, GPS and laser
scanners
• Complementary not replacement
– Typically used as part of an overall survey methodology
– Typically used in conjunction with other equipment/techniques/
methods


Wessex Archaeology

Practicalities (TLS)
• Costs of ownership
– Expensive hardware and software
– Hire vs purchase
– Partnerships
• Skills
– Survey design; how to structure a
survey
– Field survey; how to undertake a
survey
– Data processing; how to prepare
& handle the data
– Visualisation, Analysis &
Interpretation; working with &
producing outputs from the data
• Data
– Massive datasets


Wessex Archaeology

Practicalities (ALS)
• Costs of data
– Relatively inexpensive to
purchase off the shelf
– Expensive to capture new data
• Skills
– Data processing; how to prepare
& handle the data
– Visualisation, Analysis &
Interpretation; working with &
producing outputs from the data
– Using the data as 3D data vs
static imagery
• Data
– Massive datasets


Wessex Archaeology

Global Navigation Satellite Systems

• Useful in a range of situations
– Topographic survey / RCHME style earthwork survey
– Geolocating other surveys eg TLS
• Rapid setup
– Smartnet; dGPS but without the base station
– Corrections received over mobile network
(GPRS/GSM)
• Easy to use
– Nearly all Wessex Archaeology archaeologists trained
to use Leica Viva systems
– Shared interfaces with TS


Wessex Archaeology

Photogrammetry

• A very old & respected technique
• Used to great effect on many projects
– eg original English Heritage / IBM 3D model of
Stonehenge
• Costly in terms of manual processing
• Was seen by many as superceded by laser-
scanning
– Wrong! Laser scanning just another tool
• New life thanks to automated systems
– 123D Catch, Bundler


Wessex Archaeology

Unmanned Aerial Vehicles
• Range of types
– Gyrocopters
– Fixed wing
• Range of payloads
– RGB HD cameras
– Multi-spectral imaging sensors
• Can be used to provide
imagery for photogrammetry
– Wide area, high resolution
topographic survey
– Very cost effective
– 3cm resolution DSM or better


Wessex Archaeology

Workflows

• New techniques, new workflows
– Traditional/specified approaches may not be best
suited
– Traditional/specified outputs may be not be what is
required
• Clients may not know how to achieve what they
want
– Consultation in advance
– Recommend appropriate techniques to achieve
outcomes


Wessex Archaeology

Case studies


Wessex Archaeology

Tamworth Castle
• Original spec for
photogrammetry
– Way too expensive!!
• Existing laser scan dataset
(recycle award…?)
• New photographic survey
– Ground & aerial
• Combined to produce
stone by stone elevation
drawings
• No need for resurvey
– Cost effective
• High quality product
– Prepared to EH Metric
Survey specifications


Wessex Archaeology

Tamworth Castle


Wessex Archaeology

Sandsfoot Castle
• Requirements:
– topographic survey of interior & immediate environs including earthworks
– Stone by stone elevation drawings as record
– Panoramic photography
• Restricted access: dangerous structure (crumbly castle on cliff edge!)
• TLSCAD+GIS
– Drawn elevations
– DSM & contours


Wessex Archaeology

Sandsfoot Castle


Wessex Archaeology

Wakehurst Place
• National Trust property
• Complex external elevations
• Drawn elevations, floor plans, etc
– Traditional products
• Combination approach
– Direct & Indirect survey techniques
– image based methods (rectified photography, images+scan
data)
• Survey control network
– Closed loop traverse
• Located using GNSS
– OS map a little out…


Wessex Archaeology

Wakehurst Place


Wessex Archaeology

Salisbury Plain

• Monitoring of earthworks
– Topographic survey using
TLS
• Restricted access
– Short fieldwork duration
required
– Weeks for GNSS vs days for
TLS
• GIS based analysis
– DSMs
– Derived products; slope
– Models of change


Wessex Archaeology

South Wales

• 19 airborne LiDAR
datasets
• 40km2
• 133.5 million data
points
• 2 surface models Elevation component Intensity component

– Unfiltered elevation
– Intensity
• Transcription of
features
– NMP style


Wessex Archaeology

Tree graffiti
• Record and enhance tree graffiti
– Historical WWI and WWII graffiti warped
by tree growth
• Unwrapping & regression
– Challenging!


Wessex Archaeology

Stonehenge carvings

Left: (top to bottom) stone 3, stone 3 with ‘axes’ highlighted, stone 53 and stone 4

Above: stone 3 lit from below

Right: accessibility shading


Wessex Archaeology

Integration & Analysis: GIS
• Stonehenge Visitor Centre
• Environmental Impact
Assessment
– Modelled proposed structures &
tree planting
– LiDAR DSM @ 1m resolution
– Analysed potential visual impact
on >500 archaeological sites
– Probablistic viewshed model
– As built + 5,10,15yr models
– Many many viewsheds!


Wessex Archaeology

Hamdon Hill

• Topographic survey of earthworks
• Hillfort containing quarry
• Combination approach: Laser scanner
+ GPS


Wessex Archaeology

Tidworth garrison
• Record garrison in
advance of
redevelopment
• Visualisation of
existing buildings
and their context
• Used to target
further recording
works
– Direct Survey
using (TST)
• 0.75 km2 surveyed
• 37 buildings
• 25 billion
measurements
• 18Gb data file
• 10-25mm effective
resolution

Wessex Archaeology

Amesbury Archer bones
• Morphological
analysis of skull
– Cross-sections
– Measurements
– Profiles


Wessex Archaeology

Salisbury Plain

• R&D in collaboration with Leica
• Effectiveness as topographic survey tool
where vegetation is present
– Automated vegetation removal
– Manual workflows


Wessex Archaeology

Thanks!
• Thanks to:
– English Heritage
– Archaeoptics For more info:
– 3D Laser Mapping www.wessexarch.co.uk/geomatics
– Kubit www.archaeogeomancy.net
– LatimerCAD p.cripps@wessexarch.co.uk
– Environment Agency
– Warner Land Surveys
– Leica
– Tamworth Borough Council
– Weymouth & Portland Borough Council
– National Trust
– Aspire Defence
– Defence Estates


Capturing & working with 3D data in heritage contexts

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