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3.6 Creation of multiple digital objects from a single physical one

It should already be evident that there are a number of complex steps in the movement from physical object to digital representation. The process starts with a number of independent scans (from six to many more) that are then merged into a single digital object. The data were then output in OBJ format. As each of these digital objects contains somewhat different but closely related data, it is essential that key steps in the process be recorded in the metadata associated with each digital object to inform future users.

In summary, the following sequence was applied to each physical object and yielded the related digital objects:

  1. Acquisition of multiple individual scans
    1. Resulting digital objects are multiple individual scans — typically 6-12 or sometimes more — maintained in both instrument-native binary and/or ASCII formats
      1. consisting of 2.5D depth maps and co-registered colour image maps
      2. each represented in a unique coordinate system
  2. Alignment of multiple scans into a single coordinate system.
    1. Resulting digital object is still considered a collection of individual scans but now with transformations into a unified coordinate system
      1. and maintained in both native binary and ASCII formats
  3. Processing of aligned scans to pre-mesh format. Editing includes overlap reduction and additional manual edits to remove scan errors, etc.
    1. Resultant digital object is now considered a point cloud in that remaining points are thought to represent the surface of the object. This is a key intermediate digital object, as all resultant meshed objects will derive from it. It is maintained in ASCII format
  4. Creation of a final high-resolution polygon mesh digital object
    1. This is a single 'full resolution' meshed digital object that is necessary for many further derived products and for scholarly analyses and is maintained in a OBJ file format. It has undergone hole filling, despiking, optional smoothing, and other editing operations
  5. Creation of various derived digital objects (if desired)
    1. These may have different data resolutions and provide the data in different formats for viewing and reusing the data in other applications
      1. 3D-PDF
      2. X3D
      3. Low-resolution OBJ

In addition to the various digital objects there were also a number of collateral data objects collected during the process or from other sources, including various photographs and database entries describing each object. Later in this article we will discuss the challenges that this processing structure creates for the development of metadata and archival procedures.

The recording, processing and archiving of objects obviously involves a number of technically sophisticated steps and involves the use of equipment that is not inexpensive. The costs for high-quality scanning systems can range upwards from many tens of thousands of dollars/pounds/euros. There are lower resolution instruments for much less. However, these do not, at least currently, support detailed digital metric analyses but they are useful for digital 'display' purposes. The process and labour needed to scan an object clearly varies with the complexity and other properties but for the Hampson and Amarna collections a 'typical' object could be scanned within 15 to 60 minutes and processing of the data to the finished digital versions required some 4 to 6 additional person hours.

Is this investment worth it? It appears to us that the answer to that question resides in these three subsidiary questions: (a) what analyses/studies can be done with these digital representations that cannot be done with the physical ones (if anything?) (b) how valuable is increased access to the data and (c) how important is a digital record when the physical object may not be accessible? We suggest a series of analytical operations that both parallel traditional analysis and newer methods that are enabled by digital representations. The second and third questions are important to consider. In order to study an object it is usually necessary to travel to the location (museum, site, etc.) and take measurements/observations. With a digital object the object can come to you, eliminating the travel and access elements. Perhaps more significantly, however, the digital object provides a permanent point of reference for future scholarship. If a future scholar questions a conclusion or wishes to replicate a study, the availability of a digital version dramatically improves the process. In many cases access to the actual physical object may be restricted for any one of a number of reasons (e.g. governmental policies or collections restrictions) and the digital surrogate can (at least in part) remedy this limitation. Finally, we can anticipate that some physical objects may be destroyed, lost or damaged. Digital versions taken in advance of this loss would then be invaluable.

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