In 2022, a real estate developer began constructing a new hotel and office building on an empty lot in the capital city of Vilnius, Lithuania; however, workers discovered the foundation of a water treatment station built between 1910–1914 during excavation of the site.
Archeologiniai Projektai, MB, an experienced archaeological research services company, was brought in to document the structure and assess its historical significance for the Department of Cultural Heritage in Vilnius before work could proceed.
Excavation site of new hotel and office building in Vilnius. Courtesy: GeoNovus.
To accomplish this task, archaeologist Mantas Daubaras chose to utilize scanning technology to create a digital record of the remaining structure. With the assistance of Trimble distributor GeoNovus, the point cloud data and existing 2D drawings and old photographs were used to create an accurate 3D model of this early 20th century building.
Data Capture and Processing Workflow
Step 1: GeoNovus first scanned the excavated foundation, an area of approximately 550 square meters, with a Trimble® X7 3D laser scanner. The crew collected point cloud data and photo panoramas at 44 scanning stations, with each station taking about five minutes. Total on-site time was approximately 4–5 hours.
“We saw many advantages in capturing a 3D scan of the uncovered structure because of the scanner’s efficiency, speed, and precision,” said Mantas Daubaras, Archeologiniai Projektai, MB. “We were able to digitally preserve the remnants of the water station in amazing detail and create an accurate representation.”
The Trimble X7 3D laser scanner captured detailed point clouds of the foundation. Courtesy: Mantas Daubaras.
Step 2: The crew measured eight ground control points (GCP) with a Trimble Catalyst™ GNSS positioning service and DA2 GNSS receiver for georeferencing the project to the local LKS-94 coordinate system. GeoNovus activated its Catalyst 1 subscription to achieve the highest accuracy level of one centimeter.
Some of the scanning stations were registered in the field with Trimble Perspective software. Other stations scanned with less overlap were manually registered in the office using Trimble RealWorks™ office software. Daubaras used the georeferenced .e57 point cloud to draw a 2D plan of the original foundation.
Step 3: Original paper blueprints for the water treatment station were scanned and uploaded to SketchUp® 3D modeling tool on top of the point cloud to produce a draft 3D model. Due to the blueprints being in various scales, GeoNovus adjusted the model to match the actual foundation dimensions. One photo from the early 1900s showed that the building was built slightly differently than the design shown in the blueprints, resulting in further adjustments. In total, the SketchUp modeling work took about three days.
Original paper blueprints provided necessary details for the SketchUp model. Courtesy GeoNovus.
Step 4: The SketchUp model was refined with the georeferenced GCPs and imported to the Trimble SiteVision™ augmented reality system to be viewed at a 1:1 scale at the construction site. The visualization allowed the research team to better understand the spatial relationship between the original building and the current surroundings.
Using Trimble SiteVision augmented reality, the 3D model was viewed on site. Courtesy: GeoNovus.
Comprehensive Scan Data
Digital technology offers new opportunities for preserving historically significant archaeological sites. Laser scanning is fast and comprehensive, the 3D point clouds support modeling and re-creating the original structure, while SiteVision allows visualization of the structure at the scene in real time.
“Scanning and 3D modeling allowed us to capture important historical information without unnecessarily delaying development of the site,” said Daubaras. “I recommend this approach for creating visually striking images and bringing back to life buildings and city panoramas for guests and residents of the city.”
The Board of the Department of Cultural Heritage was impressed by the results of the 3D scan and the fact that the structure was preserved indefinitely as a point cloud. Quickly collecting data and producing a visualization satisfied the regulatory requirements so that construction could proceed.
“We recommended using the laser scanner to collect the data because it was faster than working with a total station, and the 3D point cloud provided more detailed information about the structure,” said Sarunas Prokopimas, CEO at GeoNovus. “The workflow we used in this pilot project demonstrated how easily this technology could be applied to other kinds of architecture, engineering and construction projects as well.”
Original water treatment station circa 1914 compared to 3D SketchUp model. Courtesy: GeoNovus.