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Modern information technologies, especially 3D scanning techniques, can be a substantial aid in
documenting and preserving the state of heritage monuments.
Inside the Tillya-Kori madrassa, in Registan Square (Samarkand, Uzbekistan), there is the city's main
mosque known as the Golden Mosque. An earthquake in the 19th century caused the outer dome of the
Golden Mosque above the drum to collapse. The dome of the Golden Mosque was rebuilt in the 1970s.
During the rebuild a number of errors were allowed, such as the use of bricks instead of ceramic tiles in the
outer layer of the dome and a large amount of building materials, unnecessarily increasing the weight of
the outer dome. As a result, it was suspected that the weight of the outer dome was causing the foundation
of the mosque building to subside. The management of the Registan Ensemble Museum carried out recently
a renovation which included dismantling the outer layer of the dome and replacing with a new one.
As an aid to this a team of scientists from the Lublin University of Technology (Poland) in June
2018, performed a 3D scanning of the interior of the Golden Mosque in order to, on the basis of the
geometry of the base of the inner dome, assess the size of the subsidence. A Terrestrial Laser Scanner (Faro
Focus) has been used during measurement. During the scan, 7 partial scans were performed in the settings
compliant with the mosque layout and measurement spots were chosen on the inner dome ring.
It allowed for the measurement of the inner dome leveling. The dome is located over 14 meters above
the floor and the direct measurement would require construction of scaffolding and closing the mosque for
tourists and faithful, which was inacceptable for the authorities. Possibility of utilizing 3D scanning without
interrupting normal tourist traffic was a solution. The self-levelling ability of the scanner ensured that each
of the partial scans performed was levelled with an error of no more than 0.015°. Using that error value and
the diameter of the dome base: d=10.75m the absolute error of dome levelling using the 3D scanning
method is 0.283cm.
The results of the measurements confirmed that the dome tilts from the level to a minimum of 23.12
cm with the diameter of the base of the inner dome just over 10m. The measured tilt is significantly bigger
than the possible measurement error which is estimated to be less than 0.1% of the measured value.
Following a secondary scanning has been conducted in year 2021 – just after the dome replacing by
a new one. The setup of scanning positions and measurement spots has been kept same to the prior scanning.
It revealed an increase in tilt of 1.14cm maximum. That tilt increase is still several times bigger than
measurement error thus confirming the change in the dome leveling.
The presented technique confirmed the thesis about the foundation of the mosque building to subside
unevenly. The measurements conducted so far cannot answer the question if the renovation of the dome
has contributed to slowing down the process of the building subsiding. The renovation took place in the
last part of the 3 year time frame between measurements. Further measurements should be performed afterhe same time period (in the year 2024) to check whether the renovation has stopped or slowed down the
subsidence. It can be done earlier (e.g. in 2022).
The presented method of digital documentation of monuments has proven to be worthy and cost-
effective method of acquiring reliable data about the heritage object current state, which gathered once can
be utilized for many scientific purposes.
This research was funded by Polish National Agency for Academic Exchange (NAWA), grant
number PPI/APM/2019/1/00004.
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