More Than One Way to Scan a Cat

Published: Tuesday, November 12, 2013 - 14:05

Although 80 percent of Accurex’s business lies in the industrial application of precision metrology and scanning, the company always enjoys the occasional cultural heritage project. When the Accurex team was called upon to scan the Sphinx of Hatshepsut, it was ready for the challenge.

Hatshepsut was the principal queen of her half-brother, Pharaoh Thutmose II. After he died she became regent for Thutmose III, her stepson and nephew. She adopted the title of Pharaoh, making her the young prince's senior co-ruler. Sculptures of Hatshepsut soon depicted the queen in male regalia.

After Hatshepsut died, Thutmose III ordered the dismantling of all male representations of her. Thousands of statue fragments, discovered in two pits near Hatshepsut’s funerary temple, have been painstakingly reassembled by scholars at the Metropolitan Museum of Art.

Figure 1: Sphinx of Hatshepsut

The Colossal Sphinx of Hatshepsut, which was scanned by Accurex Measurement, is most likely one of a pair of protective works that were placed symmetrically on the lower terrace of Hatshepsut’s mortuary temple, Djeser-djeseru (“Holy of Holies”), in the western Theban site of Deir el-Bahri.

The sphinx’s body is a recumbent lion and its head is that of Hatshepsut adorned with the male royal headdress and false ceremonial beard. It has a bull’s tail that is indicative of ancient Egyptian royalty’s powerful procreative ability.

Scanning the sphinx

Figure 3: Scanning the sphinx

The Sphinx was scanned using a Breuckmann SmartScan white light scanner that produces high-resolution 3D scans with millions of data points. Although the close-range scanner is a robust solution for industrial and engineering applications sucxh as quality inspection and reverse engineering, it generates 3D scan data that is also very useful in archeology, paleontology, and cultural heritage applications for dimensional analysis and study. 

Figure 4: Photogrammetric reference targets

For a project such as this, which contains many hundreds of scans, automatic alignment of the scans is a useful capability. The graphical representation of the scans on the screen shows in which areas data are missing, and these gaps can be closed by taking additional scans. The technique of automatic alignment cuts down on the number of scans that would be needed if a method such as using the geometry of adjacent scans were used for alignment purposes. Using the geometry of adjacent scans to align them would require approximately 50 percent more scans.

Figure 5: Scanner projects fringe patterns

The basic scan of the sphinx was conducted using the Breuckmann scanner set to a large (700 mm) field of view. A unique capability of the scanner is that it can be easily and quickly reconfigured to a smaller field of view by switching the carbon-fiber base bar between the camera and projector. This was especially useful for this application because certain areas on the sphinx, such as those between the forelegs, contain intricate hieroglyphics. For these areas a scanner configuration with a field of view of 200 mm was used. Because each scan captures the same number of points but over a smaller area, much higher resolutions can be achieved.

Figure 6: Automatic recognition of photogrammetry
targets

Results

More than 200 scans were required for complete coverage of the sphinx. The completed model contained many details that are difficult to see with the naked eye. The final result was delivered in STL format, which can be used for analysis, archiving, or creating replicas.

Recently, Hatshepsut herself has been in the news. Her remains were long considered lost, but in June 2007 a mummy from Tomb KV60, known as the “Strong One” was publicly identified as her remains by means of a DNA comparison with the mummy of Ahmose Nefertari, Hatshepsut’s grandmother.

Figure 7: Final model showing individual overlapping scans

About The Author

Accurex

Accurex has years of experience in precision dimensional metrology and scanning. Accurex has expanded its product offering to include a range of advanced portable 3-D coordinate measurement systems. We have been expanding our staff with highly experienced individuals to bring knowledge and ideas that help us understand the issues and challenges facing your business.