St canice cross_surface_riconstruction_arland_2013

Digital Recording & Community ArchaeologySt. Canice’s Graveyard, Finglas

Date of survey: Sept. 2011

Ruth Johnson, Dublin City ArchaeologistAndrea Acinelli, Survey & Mapping Division (DCC)

John Tierney, Eachtra Archaeology Ltd. (Historic Graves Ireland)

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Digital Recordingof the “Nethercross”

St. Canice’s Graveyard, Finglas

Date of survey: Sept. 2011

Ruth Johnson, Dublin City ArchaeologistAndrea Acinelli, Survey & Mapping Division (DCC)

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2013, Dublin

Location map showing Finglas and Tallaght, the “two eyes of Ireland”.ArcLand

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Finglas

Tallaght

City Centre

Osi Barony map from 1886 showing the Baronies of Nethercrosss and Uppecross.ArcLand

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Nethercross

uppercross

Map of Finglas Village (1869) showing location of High Cross and ortho image (2008) showing modern context.

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N2 National Road

High Cross

St. Canice’s Graveyard

St. Canice’s Graveyard

High Cross

Historic photo ( early 20th Century) and antiquarian sketch (19th Century)ArcLand

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Finglas Heritage Trail

Designed by Yellowstone for DCCArcLandConference

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2013, Dublin

Finglas Heritage Trail

Designed by Yellowstone for DCC

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Why? (1)

Accurate & complete digital record of the geometric information to use for:

• Art historical analysis andarchaeological analysis

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Why? (1)

Laser

Nakedeye

Scanning

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Accurate & complete digital record of the geometric information to use for:

• Condition monitoring• Raising awareness - community & education• Multimedia publication• Other

…. Because now we can!

Why? (2)

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How?

In 2011 Survey & Mapping Division (DCC) evaluated and recognized the benefits for introducing remote

sensing technologies:

Acquired a Phase-Shift Laser Scanner (Faro 3D)

Developed technical skills

Upgraded hardware

Improved network storage and communication

…... a time consuming process!!

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Spatial information from different 3D Acquisition Systems

3D Model

Range-Based

Reality-Based

Image-Based

GPS

Total Station

Lidar

Laser Scanner

Satellite Imagery

Arial Photogrammetry

Close-Range Photogrammetry

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Data collection (1)

1 Day field work (sunny day!!)

Equipment:

Faro 3D laser scanner (hired)

Trimble 5800 GPS receiver

Trimble S8 total station

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Data collection (2)

Laser scanning survey:

9 scan stations (2.5m to 5m from the cross)

10 reference objects: 7 spheres and 3 flat targets

Scans details:

Scans resolution 3mm

Overlap between scans 40-50% (final res. 0.5 – 1.5mm)

Over 9GB of data collected & …... “millions” of points

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Data collection (3)

STN1

STN2

1-2

3-4

5-6

7-8

9

Survey stations

Scanner positions

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Data Processing (1)

Manual recognition of all targets was very quick & reliable

Scans registration using “Scene” software (by Faro)

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Data Processing (2)

• Segmentation• Noise reduction • Outliers removal• Decimation • Merging

MeshLabOpen Source Software

Point cloud pre-processing

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Data Processing (3)

• Vertex normals are computed• Very dense point cloud• Object completely covered

MeshLabOpen Source Software

Poisson Surface reconstruction

It works very well if:

It create a closed and water-tight surface.

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Data VisualizationBasic visualization methods

MeshLabOpen Source Software

Points

Wireframe

Shaded

Shaded

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Data Visualization MeshLabOpen Source SoftwareTools for enhancing surface shading

Ambient Occlusion

Mean Curvature

ZBrush

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Thank you!