A MULTI-SCALAR PHOTOGRAMMETRIC RECORDING APPROACH IN TERMEZ (UZBEKISTAN)

: This paper presents the preliminary results obtained during the 3D recording campaign carried out in 2018 by the Spanish-Uzbek IPAEB mission in the archaeological site of Termez (southern border of Uzbekistan). Ancient Termez is an important historical city within the Silk Road located in the ancient Bactria region. The archaeological work performed at the site since the beginning of the 20 th century allowed a large fortified urban complex to be identified that includes other walled enclosures inside it, i.e., a Hellenistic-Seleucid fortress founded after the campaigns of Alexander the Great in the late 4 th century BC, several Buddhist monastic complexes dated to the Kushan period (1 st to mid-3 rd centuries), and a large urban settlement dated to the Islamic period which includes the city proper or shahristan and the suburbs or rabad . After the destruction by Genghis Khan in 1220, Termez was rebuilt following a different plan. Major changes involved the movement of the pottery workshops from the rabad to the previous shahristan . The research focuses on: a) the identification, study and archaeological contextualization of ceramic production centres located in different areas of the ancient Termez from the Kushan to the Islamic period (1st to 14th centuries AD); b) the integration of the pottery workshops into the general topography of the site and c) the study of their evolution in relation to the transformation of the urban design. Since the site is currently located in a military area – close to the border area between Uzbekistan and Afghanistan –, the archaeological work is restricted to specific zones and the use of aerial devices such as drones is forbidden. However, this research requires both micro and macro spatial approaches to accurately record all the archaeological structures and to evaluate the integration and evolution of the pottery workshops into the general topography of the city. In order to fill this gap, declassified images of the CORONA satellite program were analyzed and compared to historical and archaeological data. In addition, we propose a geometrical and graphical recording and distribution system of the kilns –located in the rabad and the shahristan –and the ceramics produced and used in Termez during the period studied by means of photogrammetric techniques. The results are aimed at management through open-source 3D formats and web mapping GIS libraries combined with historical satellite information that defines the different archaeological areas.


INTRODUCTION OF THE ARCHAEOLOGICAL SITE: TERMEZ (UZBEKISTAN)
Termez is located on the right bank of the Amu Darya and near the mouth of its tributary, the Surkhan Darya.The region of Termez is characterized by an almost flat topography (mean altitude 300 m) and a few small hills that are the southernmost residual reliefs of the Baysuntau-Kugitangtau range.The Amu Darya-Surkhan Darya floodplain forms part of the Afghan-Tajik depression which comprises a Hercynian basement formed by highly metamorphosed Precambrian-Palaeozoic rocks and by Permian-Triassic sedimentary and volcanic rocks.The city was one of the most important urban centres in northern Bactria/Tokharistan, a historical region that included the present-day territories of southern Uzbekistan and Tajikistan (Figure 1), and northern Afghanistan.The exact date of the founding of Termez is unknown.It has been related to the campaign to conquer the ancient Bactria and Sogdiana by Alexander the Great (between 329 and 327 BC) as well as dated in the period of the first Seleucid kings (Leriche 2001;Pidaev 2001;Leriche/Pidaev 2007;Leriche/Pidaev 2008).
Termez includes several walled enclosures inside it.The earliest of them has provided evidence of Greek occupation.Thus, pottery in Hellenistic tradition has been recovered in the lower levels of the fortress (Citadel) located on the right bank of the Amu Darya.According to their features, the vessels should be dated to the late 4th or the early 3rd centuries AD (Pidaev, 1991).The second enclosure (Tchingiz Tepe) is located North-West of the Citadel.A recent archaeological investigation carried out in several sectors by our team, comprising a complete study of the archaeological sequence supported by radiocarbon analysis, allowed to date the construction of the walls between the early 2nd and the mid-1st centuries BC.Therefore, the walls of Tchingiz Tepe could be dated immediately after the arrival to the region of the nomadic tribes known by the name of Yuezhi (Martínez et al. 2014;Gurt et al. 2015).Under the rule of Kushan kingdom (1st century ADmid-3rd century AD) a new fortified area, the sharistan, was built.During this period, Termez became an important religious centre that hosted a number of Buddhist monasteries such as Fayaz Tepe, Kara Tepe, Tchingiz Tepe and Zurmala (Abdullaev, 2013;Stavisky, 2001).The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XLII-2/W15, 2019 27th CIPA International Symposium "Documenting the past for a better future", 1-5 September 2019, Ávila, Spain

Image processing
The photogrammetric process includes a total of 52 control points in order to achieve better adjustment in the spatial referencing of the block of images during the photogrammetric restitution process.These points were taken in the field in April, 2018 using a GNSS sensor with sub-metric accuracy.Their distribution is related to the localization of a series of interesting archaeological elements which were worth documenting during this fieldwork campaign.These GCP occupied a small space within the whole image.Therefore, we used QGIS-digitizing tools to digitize a series of points on the georeferenced CORONA images.Although the accuracy of the resulting coordinates may be questionable, they very easily localized on the images during the photogrammetric process.This process is justified in view of the lack of a wide orthophotography of the area and of the impossibility of creating it ourselves as drones are not allowed in this zone.
We mainly used two software products for photogrammetric restitution.One is ERDAS Imagine Photogrammetry; in the non-metric cameras category we worked with focus width (609,602 mm) and the resolution used in scanning (7 µm) to set the interior orientation.This model is fit to use with the CORONA images free from interior calibration parameters of the main and fiducial points (Altmaier and Kani, 2002;Galiatsatos, 2004).We also used The Automatic Terrain Extraction tool (ATE), which allows for obtaining DEM from the restituted photogrammetric block (Bellido, 2018).
Next, we performed a photogrammetric restitution based on the SfM technique in Agisoft Metashape Professional (Watanabe et al., 2017).Like Imagine Photogrammetry, interior orientation was obtained based on focus width and scanning resolution.Fiducial points cannot be localized given that they are inexistent, thus distortion rates are left blank so that the software can calculate them during bundle block adjustment.
Following the bibliography on CORONA image correction (Shin and Schenk, 2008) and on rotation angle measurement based on GPS data (Wierzbicki and Krasuski, 2015), we carried out a first estimation of the exterior orientation parameters ( Both photogrammetric restitution processes are aimed at obtaining an orthorectified and georeferenced image.In this regard, numerous approximations have been performed by changing the images used in multiple combinations: whole images, images cut over the area of study, non-georeferenced images, images georeferenced with 2 nd degree polynomials and images georeferenced with 1 st degree polynomials (affine transformation).Furthermore, both GPS and QGIS-digitized control points have been interchangeably used to obtain the desired result.Unfortunately, we were not able to perform the DEM with the selected CORONA images due to overlapping problems between them and a lack of key data, unclassified by the NGA for photogrammetric restitution.Consequently, in order to reconstruct the DEM of recent times, we obtained altimetry data from the relief map by Dumont, Reynard and Person in the context of the French-Uzbek archaeological mission in Bactria (Pidaev, 2001a).Figure 4 shows the altitudinal data in level curves at 0,5 meter intervals and in a series of bench marks and topographic points.The localized walls and buildings of the site appear as auxiliary information providing context to the relief.
Figure 4. Interpolated 3D model of current period with the location of the ceramic kilns (above).Longitudinal section on the DEM between the T5 and T8 area of ceramic kilns (below).
As to archaeological interpretation, the image has been adjusted in different ways in order to improve the visualization of remains still buried.First, we performed basic contrast, brightness and histogram adjustments.Next, the work method's algorithms were applied to the LiDAR data, namely Analytical Hillshading, Hillshading from multiple directions, Simple Local Relieve Model, Principal Components Analysis, Sky-view Factor and Positive/negative openness.

Data acquisition
The second documentation level involved acting over different ceramic kilns in the site.Due to logistic difficulties in the field, we used those photogrammetric techniques that would allow for rapid extensive documentation.Regarding the photogrammetric system used for the data extraction of the kilns already excavated, a 5 meter pole with a micro four thirds Olympus EPM 1 camera and a Zuiko Digital ED lens 12mm f2 perpendicular to the ground was set up.The final height obtained with this system was 5,7 meters with an angle between 40° and 45° in order to facilitate data collection with a linear movement every two meters, both longitudinally and transversal to the excavation so as to obtain a redundant overlap between images that was valid for three-dimensional reconstruction.

Table 2 .
Table of the initial exterior orientation parameters of the images.
The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XLII-2/W15, 2019 27th CIPA International Symposium "Documenting the past for a better future", 1-5 September 2019, Ávila, Spain Approach Using Ikonos and SRTM Data.Photogrammetric engineering, 14.Galiatsatos, N., 2004.Assessment of the CORONA series of satellite imagery for landscape archaeology: a case study from the Orontes valley, Syria, Durham theses, Durham University.Available at Durham E-Theses Online: http://etheses.dur.ac.uk/281/