Next-Generation Positioning Technology 'Chrono Locate™': Construction Site Demonstration Conducted to Achieve High-Precision Positioning Even in Environments Unreachable by Satellite Signals

Taisei Corporation (President and CEO: Yoshiro Aikawa) and Seiko Group Corporation's (Chairman, Group CEO, and Group CCO: Shinji Hattori) operating companies, Seiko Future Creation Inc. (President: Makoto Ichimura) and Seiko Solutions Inc. (President: Jun Sekine), collaborated to conduct a demonstration experiment aimed at applying the 'Indoor High-Precision Positioning System Chrono Locate™ *²' to construction sites. This system enables highly accurate positioning even in indoor and underground spaces where Global Navigation Satellite Systems (GNSS *¹) are unavailable.

This initiative aims to extend the functionalities that GNSS has brought to construction sites—such as efficient surveying, ICT-driven construction, and digitalized as-built management—into non-GNSS environments. Furthermore, by leveraging the highly accurate and compact features of Seiko's 'Chrono Locate™,' the following applications are envisioned as part of Taisei Corporation's integrated platform, 'T-iDigital Field.'

Specifically, by combining it with advanced technologies like AR (Augmented Reality), it becomes possible to perform high-precision surveying with drones, display 3D blueprints via AR, and elevate safety management by tracking worker movement paths. In addition, it allows for highly accurate positioning and tracking of heavy machinery and construction equipment. This can supplement the surveying and position confirmation work previously performed by workers using surveying instruments.

Moreover, through this demonstration, it was confirmed that this system can acquire 3D positional information with high precision and in real-time. This makes it possible to enhance the sophistication of construction and improve productivity even in non-GNSS environments.

Moving forward, by utilizing this technology, we aim to contribute to addressing labor shortages, improving productivity, and enhancing safety at construction sites.

Driven by initiatives like 'i-Construction' promoted by the Ministry of Land, Infrastructure, Transport and Tourism, efforts to drastically improve construction site productivity through the proactive use of ICT and IoT devices are progressing across the entire construction industry. One of the representative tools is GNSS, which is widely used for efficient acquisition of positional information and the resulting digital transformation (DX) of production processes—from topographic surveying and earthwork support to the operational management of construction machinery and dump trucks.

However, because GNSS cannot be used in environments where satellite radio waves cannot reach, such as inside tunnels or underground spaces, or in construction environments where radio wave reflection occurs, the development of a new system capable of efficiently determining positional information even in non-GNSS environments has been heavily demanded.

Therefore, Taisei Corporation focused on Seiko's 'Chrono Locate™' technology, which can acquire positional information without relying on GNSS, and linked it with its integrated platform 'T-iDigital Field' to commence a demonstration experiment for its application at construction sites.

This technology achieves both nanosecond-level time synchronization and centimeter-level distance measurement simultaneously—a feat previously difficult to accomplish—by having multiple base stations set up in the targeted positioning area transmit and receive radio waves bidirectionally with mobile stations *³. While GNSS relies on one-way radio wave reception from satellites, this technology measures distance by calculating the time difference in the arrival of bidirectional radio waves. Furthermore, it achieves centimeter-level distance measurement by highly accurately synchronizing the time between devices at the nanosecond level via bidirectional communication, thereby increasing measurement precision.

This technology can be described as a 'local GPS' deployed on the ground. Instead of satellites, multiple base stations are installed in the target area, and by extremely precisely measuring the arrival time difference of radio waves reaching the mobile station, it calculates highly accurate positional information (coordinates).

【Overview of the Demonstration Experiment】 ■ Application Site 'Metropolitan Expressway Inner Circular Route (Nihonbashi Section) Tokiwabashi District Tunnel Construction' (Client: Metropolitan Expressway Co., Ltd.; Construction: Taisei-Kawada JV), part of the Nihonbashi section undergrounding project of the Metropolitan Expressway. We conducted test positioning using Chrono Locate™ to verify its applicability under the elevated tracks of the Metropolitan Expressway between Otemachi 2-chome, Chiyoda-ku, and Yaesu 1-chome, Chuo-ku, Tokyo—a construction environment where GNSS reception is unavailable.

Content We installed 12 base stations in the construction area under the elevated tracks of the Metropolitan Expressway and conducted a tracking test of a passing boat (mobile station) navigating the Nihonbashi River. Additionally, we installed mobile stations on both the driver's seat and the rear of the vehicle body of a backhoe on a pontoon boat performing dredging work, and conducted a test to track the swinging status of the boom.

Results 1. The trajectory of the passing boat tracked by this technology almost perfectly matched the results of laser surveying, confirming that the specified positioning accuracy was achieved. By operating multiple areas in combination, we covered a wide construction section and achieved continuous positioning even when the boat moved across multiple areas. 2. We confirmed that the boom's swinging behavior could be continuously and stably tracked using the two mobile stations attached to the front and rear of the backhoe. We confirmed that this can be applied to accurately grasp the dredging position in the future.

Looking ahead, Taisei Corporation plans to implement the positioning function using this technology as an application within 'T-iDigital Field,' an integrated platform that supports construction management with digital technology. Through this, we will promote the sophistication of as-built, quality, and safety management in non-GNSS environments, advancing the DX of the entire production process at construction sites.

Meanwhile, Seiko will expand this technology into diverse industrial sectors beyond construction and civil engineering—such as optimizing movement paths in logistics warehouses and factories where GNSS radio waves cannot be received, and controlling automated guided vehicles (AGVs)—thereby contributing to the construction of new social infrastructure utilizing positional information and improving productivity.

*¹ GNSS: A generic term for satellite-based positioning technologies that receive radio waves transmitted by positioning satellites like GPS (US), QZSS (Japan), GLONASS (Russia), and Galileo (EU) to enable pinpointing current locations, navigation, and acquiring accurate time. Global Navigation Satellite System. *² Chrono Locate™ is a trademark of Seiko Group Corporation (pending) and is a positioning system applying the high-precision time synchronization technology that Seiko has cultivated over many years. It integrates distance information obtained from a minimum of four base stations to accurately pinpoint the 3D position (XYZ coordinates) of a mobile station. *³ This technology incorporates research outcomes from the National Institute of Information and Communications Technology (NICT).