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5.3 Digital object metadata

Metadata for a digital object consists of several levels and is divided into two major categories 1) metadata for data collection (referred to as acquisition metadata) and 2) metadata for data processing. Acquisition metadata is further divided into two major sub-units — project and scan level. Processing metadata is characterised by key processing steps including scan registration, mesh preparation, mesh finalisation, and additional product creation. Metadata entries for acquisition and processing metadata are shown in the tables below.

Table 1: Project level metadata (Payne 2010, 3.2.1)

Element Description
Project nameName of the project
Name of monument, survey area, or objectName of object, monument, or area scanned
Monument/Object numberThe ID number or code, if applicable, of the object or monument
Survey locationExact location of survey with complete address and/or coordinates
Survey date(s)Dates(s) of survey
Survey conditionsThe overall weather trend during survey (sunny, overcast, indoors, etc.)
Scanner detailsDetails of the instrument(s) with serial number(s) and scan units
Company/Operator nameDetails of company and/or scan operator
Control data collected?If yes, then list control_file_name.txt.
Turntable used?Yes/No
RGB data capture?If yes, then specify whether:
- Internal or external?
- Was an additional lighting system used? If yes, then provide a brief description of the lighting system.
Estimated data resolutionThe estimated data resolution across the monument or object.
Total number of scans in projectTotal number of scans
Description of final datasets for archiveWhat datasets will be archived (include file names if possible)
Planimetric map of scan coverage areasIf applicable, then provide the image name.
Additional project notesAdditional notes
Images from surveyOptional, if yes, then provide the image file names

Table 2: Scan level metadata (Payne 2010, 3.2.2)

ElementDescription
Scan filenameThe name of the scan. A suggested filename for original raw scans for archiving is in this format: ProjectName_scan1.txt.
Scan transformation matrixThe name of the transformation matrix used in Global Registration
Name of monument/object area  
Survey date 
Scan number The number of the scan in scan sequence e.g. 3 of 18.
Number of points in scan 
Additional scan notes 
Scanner technology TOF/Phase/Triangulation
Data resolution The data resolution at specific range.
First or last return (TOF scans only) 
Frequency settings (phase scans only) 
Noise settings (phase scans only) 
Camera exposure settings (If RGB acquired) (phase scans only) 
Lens or FOV details (triangulation scans only) 

Table 3: Scan registration metadata (Payne 2010, 3.3)

ElementDescription
Name of registered dataset Filename for the dataset, a suggested naming structure for registered dataset for archiving: ProjectName_GR.txt
Total number of scans used in registration/total number acquired  
Global registration error in units 
Total number of points in final registration 

Metadata for each of the derived products was also needed. This included the pre-mesh point cloud.

Table 4: Pre-mesh point cloud metadata (Payne 2010, 3.4.1)

ElementDescription
Name of pre-mesh datasetThe dataset's filename, a suggested naming convention for pre-mesh point cloud dataset isProjectName_GRE.txt
Number of points in file 
Overlap reduction (Y/N) (optional)
Smoothing (Y/N) (optional)
Subsampling (Y/N) (optional)
Colour editions(Y/N) (optional)
Point deletion summary 

Table 5: Polygon mesh metadata

 
ElementDescription
Name of mesh dataset The file name, a suggested naming convention for the polygonal mesh dataset is *ProjectName_origmesh
Estimated mesh spacing (in units)
Holes filled(Y/N)
Smoothing (Y/N)
Colour editions(Y/N) (optional)
Healing/despiking (Y/N) (optional)
Total triangle count (post-editing, pre-decimation) 
RGB colour included(Y/N)
Data reduction(Y/N). If yes, give percentage of reduction from original
Coordinate system adjustment(Y/N). If yes, a transformation matrix must also be provided.
Additional processing notes  

Table 6: Decimated mesh metadata (Payne 2010, 3.4.2)

ElementDescription
Name of decimated mesh datasetThe file name, a suggested naming convention for the decimated polygonal mesh dataset isProjectName_decimesh_50pcnt for decimated mesh e.g. by 50%.
Total original triangle count 
Decimated triangle count 
RGB colour preserved from original dataset (Y/N)

A fully 'worked example' of these metadata for a single object from the Hampson Museum are provided in the G2GP.

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