Piloting Simulated GNSS in Underground Spaces

Global navigation satellite systems (GNSS)-based navigation services are widely used above ground in open-pit mining operations for safety management, process optimalization and fleet management. Extending these location-based services (LBS) to underground operations may increase efficiency and safety in mining, underground research and development, as well as, in mine reuse projects. Numerous different methods and technologies have been proposed and utilized for positioning and navigation in indoor areas and underground tunnels. Depending on the detection technology, there have been four main categories of LBS with varying levels of complexity and accuracy: 1) inertial navigation systems, 2) radio frequency (RF) based positioning, 3) multi-sensor (hybrid) navigation and 4) pseudolite-based positioning. The main motivation for deploying GNSS technology in underground conditions is to utilize the already existing, robust infrastructure, with simple off-the-shelf receiver devices. The tested system has high potential to enable high accuracy positioning in traditional GNSS-denied areas. 

The simulated underground GNSS approach is tested in a 400-meter-deep tunnel section in the Pyhäsalmi mine located in Northern Finland. At the test site, 17 signal emulators have been installed in a 200-meter-long mine tunnel to provide GNSS access. The goal is to test the simulated underground GNSS and its ability to support a wide range of common above-ground GNSS end-user devices and services. These may include applications for worker safety, mine environment monitoring and operational efficiency. The accuracy, reliability and coverage of the tested system will affect its usability significantly. In this paper, we measure positioning accuracy in different underground conditions and environments, assess applicability of a hybrid positioning approach using WLAN supported services, and test functionality of the system with common GNSS devices. The collected positioning data is analyzed with spatial analyses and statistics in geographic information systems. Results of the study will indicate how GNSS emulation techniques could be adopted to deep underground spaces and what are the possible development needs of the technology. 

This project received funding from the European Union's Horizon 2020 innovation programme under grant agreement number: 839398.