3D Capture, Representation and Manipulation of Cuneiform Tablets

S.I.Woolley, N.J.Flowers, T.N.Arvanitis, A.Livingstone, T.R.Davis and J.Ellison

Keywords : 3D imaging, cuneiform tablets, laser scanning, forensic analysis, 
data archival, data compression.

Abstract : This paper will present the digital imaging results of a 
collaborative research project working toward the generation of an on-line 
interactive digital image database of signs from ancient cuneiform tablets.  An 
important aim of this project is to enable the forensic analysis of the 
cuneiform symbols to identify scribal hands.

The paper will describe the challenges encountered in the 2D digital image 
capture of a sample set of tablets held in the British Museum, explaining the 
reasons for attempting 3D imaging and the results of initial experiments.  
Additional information can be found on the project website: www.cuneiform.net

3D Imaging of Cuneiform Tablets : Cuneiform (from the Latin word cuneus, meaning 
wedge) tablets are moulded clay tablets. Their dimensions can range from those 
of a credit card to those of a palmtop computer.  They are inscribed with 
triangular indentations made by a reed stylus.  They are amongst the earliest 
records of written communication, and contain a variety of different scripts, 
including pictographic, alphabetic, and syllabic writing. The earliest examples 
are up to 5,000 years old, and the writing technique remained in use for some 
3,000 years. The writing was deciphered in the last 150 years; hundreds of 
thousands of tablets have been discovered and are now preserved in museum 
archives.  Unfortunately, only a small fraction of these tablets can be made 
available for display and much important academic work has yet to be performed 
on the very large numbers of tablets to which there is necessarily restricted 
access.

Many of the tablets contain densely compacted inscriptions on both sides, with 
text running over rounded edges and frequently continuing along each side edge, 
making the complete 2D capture of symbol sets problematic even with many 
exposures. Our need for sign recognition and forensic analysis dictated high-
resolution capture, which proved particularly difficult in the case of the 
smaller tablets.  Conventional NTSC video cameras are convenient to use but only 
provide 480 lines of resolution.  Still digital cameras give significantly 
higher resolution although they have practical limitations. In addition, the 
depth of the impressions makes getting the lighting right both difficult and 
time-consuming.

When reading the tablets, experts tend to rotate them constantly; both grossly 
in order to present all the signs to inspection, but also subtly in order to use 
light and shadow to bring out the indentations clearly. In a digitised tablet, 
this manipulation would ideally be enabled with high-resolution 3D rendering, 
rotation control and light source adjustment. Our experiments indicated that 
sufficiently high-resolution scans are not easily realisable, and that in any 
case the resulting file sizes would prohibit remote access and real-time 
manipulation.  Experimental scans were performed using laser stripe 
triangulation at resolutions of 10 and 25 lines per millimetre producing files 
in excess of 100Mbytes. The current cost and complexity of the appropriate 
scanning processes make remote capture, formatting, storage and communication 
even more challenging.

The paper will present the results of experimental 3D laser scans from the 
smaller, more densely inscribed tablets; we will also discuss the tractability 
of 3D digital capture, representation and manipulation, and investigate the 
requirements for scaleable data compression and transmission methods.