The Khentkawes Town (KKT) - Ancient Egypt Research Associates

www.aeraweb.org
Modeling
The custom-designed, portable Zoser Scanner (ZS), was
equipped with four DEVELO Scanning Range Finders,
four 1/2-inch CCD digital cameras (C mount), a gyroscope,
a target for Leica TCRP 1205+ and a tablet PC.
The gyroscope of the ZS measures its position, orientation,
and velocity at the rate of 100 Hz (100 times per
second). The four digital cameras accompanying each
scanner took rapid sequence photographs of the pyramid
fabric (fig. 5).
The body of the ZS was automatically traced by the
Leica TCRP 1205+ at the rate of 6-10 Hz, and the data was
eventually synchronized by a GPS timer. The accuracy of
the gyroscope depends on the number of satellites, and
their orbits need to calibrate for at least half an hour after
starting. Once it starts, the device should work with an
uninterrupted power supply. If power is interrupted, the
gyroscope needs to be re-calibrated. Therefore, the ZS was
connected to a long power cord during the survey to assure
a continuous supply of electricity. The width of the
ZS wings is 2.5 m each. This required that the climbers,
Yamamoto and Sato, rappel each face about 25 times (the
monument is 109.02 m north-south × 121 m east-west ×
58.63 m high).
The scanning of the whole pyramid with the ZS was
theoretically supposed to be completed within 14 days, but
some practical difficulties, such as slow descending speed
due to deterioration of the stones and the requirement of
an uninterrupted power supply, required us to modify the
original plan. But overall, the entire coverage of the pyramid
was completed with the Topcon GLS-1000 scanning at
the rate of 5 mm mesh from 35 different positions. The top
of the pyramid, the four corner ridges, and one area at the
southern side of the southern bottom step remained the
only “shadow” areas, not covered by our scanning. This
data was integrated during post-processing.
Rendering/Data Processing
All the scanned data of GLS-1000 was integrated into
a single point-cloud model on a computer at the headquarters
of Topcon in Tokyo. Topcon’s original software,
ScanMaster, generated point-cloud representations
during post-processing. Color information from digital
photographs taken by the built-in cameras on the
scanner complemented 500 million points. We also used
photos from a conventional hand-held digital camera to
supplement color information.
After this process, Tomii created a three-dimensional
movie (1280 × 720 pixels, 30 ftp) and orthophotographs
(3,000 pixels) of a plan and sections of the pyramid.
However, due to the excessive quantity of data, it was not
feasible to export 20,000 pixel orthophotographic images
of the Step Pyramid with Pointools. So, Dr. Kosuke
Sato and Dr. Ichiroh Kanaya developed a special program
which can generate large size orthophotographic images
from the point-cloud data.
Results
Our original aim was to create an image of the Step Pyramid
as it really is rather than an interpreted line drawing. An
extensive three-dimensional point-cloud model of the
exterior of the pyramid was mainly produced by Topcon
GLS-1000(s), but supplemented by the custom creation
and implementation of the Zoser Scanner. We produced
a plan, and four cardinal elevations of the pyramid, all of
which can be printed out in a 1:100 size of the monument
at 350 dpi (see Color Plates 7 and 8).
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Giza Plateau Mapping Project Season 2008 Preliminary Report