Hop on board as we continue our journey Around the World in 80 Models! We began our itinerary at Sketchfab headquarters in New York and are working our way through Europe, Africa, Asia, Oceania, South America, and North America. To catch up on past destinations, check out the rest of the Around the World in 80 Models series.
This week the team at the Balkan Heritage Foundation takes us to the Republic of Macedonia to tell us about the Roman Temple of Isis at Stobi.
Stobi, Republic of Macedonia: Temple of Isis
We’re an interdisciplinary and international team made up of professionals from the Republic of Macedonia, Bulgaria and Canada who work under Dr. Silvana Blazevska, director of the National Institution Stobi. In collaboration with Balkan Heritage Foundation, a non-profit foundation based in Sofia, Bulgaria, and Queen’s University, Canada, NI Stobi began a pilot project in 2015 to introduce new techniques of archaeological documentation to the site, and to provide high-quality training to undergraduate and graduate students from around the world in computational photographic methods within the Balkan Heritage Field School Program. These included Reflectance Transformation Imaging, Digital Photogrammetry, Virtual Tours, Object Virtual Movies, Reflected IR/UV Photography, and Colour Decorrelation Enhancement.
The 2015 field school in the application of new 3D methods to archaeology was only one chapter in a long-standing collaboration with Balkan Heritage Foundation that began with the first field school at NI Stobi in 2010. In addition to training in traditional methods of archaeological excavation and documentation, students can also receive instruction in the conservation and restoration of ceramics and glass, as well as wall-paintings and mosaics with the talented staff of NI Stobi. The integration of new documentation technologies with tried and tested methods of recording at the object and site-scale was a natural fit for NI Stobi and these efforts have continued with the completion of a successful season in 2016 where students were instructed in the use of photogrammetry, CAD, analytical stereo-plotting and precise GNSS and Total-Station surveying techniques in order to advance archaeological research in the Republic of Macedonia.
The ancient site of Stobi, first mentioned in Livy’s Ab Urbe Condita as already an “old town” in 197 BCE, is located at the favourable confluence of two rivers, the Crna (ancient Erigon) and the Vardar (ancient Axios), and fell under the power first of Macedon in the late third-century BCE and then under Rome less than a century later. From 69 CE onwards Stobi had the status of municipium (the second highest rank among Roman provincial towns) and minted its own coins with the inscription of MUNICIPIUM STOBENSIUM.
As a result of an administrative reform in the Roman Empire at the end of the third and the beginning of the fourth century CE the Roman Province of Macedonia was divided into two smaller provinces Macedonia Prima and Macedonia Salutaris. Later, in the 5th century Macedonia Salutaris was renamed in Macedonia Secunda with Stobi as its capital. In the fourth century CE, Stobi became an important Christian center and the seat of powerful bishops. Later, in the fifth and sixth centuries, Stobi suffered from the depredations of the Huns, Ostrogoths, Avars and Slavs. The constant threat of barbarian raids as well as climatic changes lead to the gradual abandonment of the city in the second half of the sixth century CE. Some records mention a small Slav community that settled and lived there in later centuries. The last historical reference to Stobi describes the victory of the Byzantine troops over Stobi’s local militia during the 11th century CE.
A temple dedicated to the Egyptian deities was discovered at the lowest terrace of the ancient city of Stobi in 2008. In 2012 a monumental marble sculpture of the goddess Isis found in front of the temple confirmed the dedication. The discovery of a votive marble relief in 2015 proved that Isis was worshiped together with her counterpart Sarapis. The temple was erected in the first half of the second century CE as a private donation of a wealthy citizen of Stobi. It is a typical Roman temple on a high podium with two underground vaulted chambers and is surrounded by a large religious complex. A large marble altar was found in the front part of the temple and two marble pedestals for sculptures or dedicatory inscriptions on the northeastern side. The temple was destroyed in the early 5th century CE when the surrounding complex was reused as residential area.
Our team used a 36 mega-pixel Nikon D800e and a 20mm f/2.8D Nikkor lens exclusively for architectural modeling around the site in the 2015 field season, a project that included the splendid Episcopal Basilica and Baptistery in addition to the Temple of Isis. The excellent base-to-distance ratio provided by a wide-angle lens in close-range photogrammetry applications (1:1 to 1:4 in this case) meant that millimetric levels of accuracy could be achieved in 3D reconstruction, although the ground pixel-size was less than with the standard 50mm prime lens commonly used in “Structure from Motion” photogrammetry techniques. Camera calibration was performed using ADAMTech CalibCam, part of the class-leading Australian 3DM Analyst Mine Mapping Suite designed for engineering surveys.These levels of accuracy were confirmed by the use of both ground control and check-points on the structure taken with a Leica TCRM 1201+ Total Station with 1 arc-second angular accuracy; the final standard-error of the control network adjustment was 3mm, within the Second Order specifications of the NI Stobi control network earlier established by the Leica Geosystems representative in Skopje, Dr. Aleksander Postolovski of GeoWILD MAK. The final photo-realistic textured model for Sketchfab was output using Agisoft Photoscan Professional at the “High” setting (one-half resolution images). The dense point cloud comprised of 3 770 330 points. The mesh uploaded to SketchFab, with only minor editing, has 745 066 faces, 378 003 vertices.
In addition to the photo-realistic model posted to Sketchfab, our team also derived several valuable scientific outputs from the point-cloud data using PointCab Suite, a very fast and intuitive tool that allows us to extract 2D, georeferenced sections and elevations from the complex structure for subsequent inclusion in the AutoCAD site plan.
The cross-section below shows how techniques of underground photogrammetry used in the mining industry could be deployed to capture the small interior chambers of the temple. This interior data was aligned with the outside model by means of control points shot from a total station traversed into the chambers themselves.
Our team at NI Stobi looks forward to posting more of our work on Sketchfab, on both the artefact and site-scale, and welcome questions from the public and scientific community.
To see more of the Balkan Heritage Foundation’s models here on Sketchfab, check out their profile.