High Definition Digital Documentation (H3D): Applications to Architectural and Landscape Heritage Preservation

Terrestrial Laser Scanning (TLS): Applications to Architectural and Landscape Heritage Preservation Part 1

1What is TLS?TLS is an integrated suite of three-dimensional spatial technologies that have significant applications to the preservation of cultural heritage across multiple scales.

2TLS Uses:H3D is an innovative and versatile set of tools for archaeological research.It can be brought to an archaeological investigation to assist in the development of highly accurate models of the site and the surrounding landscape.It can be used to augment prior work and to create accurate maps and models and to conduct spatial analysis.These methods can help to eliminate subjective decisions.

3Scale of Analysis

4Short Range

Kaminaljuy Stela 105Mid Range

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Long Range

7More on H3D:Alliance for Integrated Spatial Technologies, University of South FloridaLaser scanning is a non-contact, non-destructive, and non-invasive method to acquire extremely accurate high resolution data that can be used to analyze, model, and monitor architectural structures and their supporting physical elements. Terrestrial Laser Scanning is a primary component of an H3D approach 8Equipment Dynamic Range Level of Accuracy Points per second

1500 meters 7 mm at 100 m 2,500

300 meters 4-6 mm at 50 m 50,000 70 meters 3 mm at 25 m 120,000

Examples of long and mid range terrestrial laser scanners

9Types of Laser ScannersTOF- Time of Flight short duration burst pulse, used for longer range, less points collected.Phase-based scanner continuous beam, measures the phase difference, used for shorter ranges (~50 to 100 m), high scan rate and accuracyTriangulation-uses laser light to probe the environment. Shines a laser and uses a camera to look for the location of a laser dot. Depending on how far away the laser strikes the surface, the laser dot appears at different places in the camera's field of view. Called triangulation because the laser dot, the camera, and the laser emitter form a triangle with a known position. Can be highly accurate, used for short range, control for environment needed. Structured Light- Structured-light 3D scanners project a pattern of light on the subject and look at the deformation of the pattern. Highly accurate, perhaps better with shiny surfaces, high degrees of environmental control needed.Also, handhelds, hybrids and very low cost options

Time of Flight Laser Scanners

Long Range Terrestrial Laser Scanning (TLS)Also called ground based LiDAR

Alliance for Integrated Spatial Technologies University of South Florida 12Phase-shift scanners

Triangulation

Architecture with Phase Shift

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20Scale Differences that Matter

Alliance for Integrated Spatial Technologies University of South Florida

21Light Detection and Ranging (LiDAR)

Space, Airborne, and Terrestrial laser scanningAirborne Laser Scanning (ALS) Laser scanner mounted on airborne platform Surface models generated from point clouds Often Integrated with Terrestrial Laser Scanning (TLS)

Alliance for Integrated Spatial Technologies University of South Florida 22Point CloudsScanner measures range, azimuth and vertical angle (X,Y, Z plus intensity- and some can add color images quite easily)Gridded data means that you have uniform point spacingpoint clouds have randomly spaced dataPoint clouds are random (not in a grid) creates issues for data storage and analysis big datasetsGrids are more predictableclouds are so dense that you dont see points.

Huge data sets and increases continuing to be seen in scan ratesindustry keeps increasing speed of scanning, and that increases the size of datasets captured. Leads to issues in storage, retrieval and managementCan be mobile or fixed

23Point Clouds

Environmental conditions that effect scanner range and qualityLight daylight reduces range and increases noise in scan. Possible Solutions: scan on overcast or evening conditions; reduce range to targetSurface Qualities shiny, highly reflective surfaces are difficult to scan. Solution: decrease range, increase angle to objectColor darker objects reflect less light. Solution: decrease range, add powder coating, (d)Movement Scanner and target object must both be stationary

25Field and Lab Post-Processing: Microsoft Windows XP, 2000 (Vista for workstations)1 GHz processor (2.5 GHz recommended)1GB RAM(4 GB recommended)Wheel mouse with 2 buttons Graphic card with OpenGL hardware acceleration - 32MByte on board memoryEthernet-card for licensing

26Points to Consider:

What are the short-term and long-term research questions?What is the intended use for the data? Types of projectsCultural sensitivity Potential hazardsWindow of opportunityRegistrationNo registrationLocal registration Global registration LogisticsAccess to first aid Access to the project areaAvailability of Power supplies Access to additional materials Storage facilities Number of personnel required Budget

27On-site Details:Geometry scanner and reference target set-up positions Positioning the ScannerThe scanner will record only what it can see This means that the references and the target object must be in the line of sight of the unit.For registration each scan requires a minimum of 3 visible references; these references should be evenly spaced around the scanner. For better control use 4 references per scan.

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