From September 5 to 6, the G20 Summit took place in St. Petersburg. On the first day, participants were presented with a laser show, using the Grand Palace and the Grand Cascade of fountains in Peterhof as the projection “screen”. To ensure that all visual effects looked as realistic as possible, the developers needed to calculate every step with extreme precision. Highly accurate calculations required a detailed 3D model of the Grand Palace and the Grand Cascade.
To implement the laser scanning and 3D modeling project, the G20 organizers chose Trimetari Consulting. During the fieldwork, the company’s specialists used a ScanStation P20 laser scanner from the Swiss company Leica Geosystems.
The device has several technical features:
– Accuracy: The scanner allows measurements at a distance of up to 120 m (at 18% reflectivity) with high accuracy (1 mm) and speed (1,000,000 points/s).
– Weather resistance: The Leica ScanStation P20 has a high level of dust and moisture protection (IP54) and is the only high-precision scanner that allows work at temperatures down to -20°C.
– Self-calibration function: The Leica ScanStation P20 can be calibrated without the intervention of a service center.
The project work consisted of two stages: field and office.
1. Field stage – laser scanning of the part of the Grand Palace facade facing the Lower Park, and the Grand Cascade. The survey was conducted in a local coordinate and height system. The field stage was completed in 1 day. Peterhof is a popular tourist destination, and the large number of museum visitors caused some difficulties. Dense crowds of people not only limited the visibility of the building’s facade but also obscured the targets used to stitch the scans into a single coordinate system. For this reason, targets were placed with greater density and, where possible, higher than human height, totaling around 100 targets. During the fieldwork, the targets were not scanned separately in the field but were recognized later in the office phase using Leica Cyclone software.
In total, 16 instrument setup points were made. This number was sufficient to cover the entire required survey area. At each point, 360° scanning was performed with a resolution of 3 mm at 10 m, along with panoramic photography. As a result of the fieldwork, a point cloud and panoramic photographs were obtained, which can be used to colorize the point clouds in real colors. With a scanning detail of at least 1 point per 1 cm², the resulting accuracy was estimated at 1 cm (RMS error).
2. Office processing. During the processing stage, scan registration and the construction of a 3D model of the facade and cascade were performed. The result of the work was presented as a point cloud in ASCII TEXT (XYZIRGB) format and a 3D triangulated polygonal model. In accordance with the Terms of Reference (ToR), the facade walls, risalits, visible part of the roof, pediments, pilasters, window and door openings, and the external part of the window fillings were modeled. The modeling process itself involved fitting geometric primitives into the point cloud. Sculptures and other complex-shaped elements were modeled using tools that wrap the point cloud with TIN surfaces.
The result of the modeling was a 3D triangulated model in OBJ format.
The 3D model was used to create a laser show of unique scale. For the video mapping, 18 powerful projectors were used, projecting the image onto a 293-meter-long facade. Recordings of the laser show can be viewed on YouTube.