Incorporating GNSS into the First Responder Tracking Prototype

Abstract

In emergency scenarios, accurate and continuous positioning of First Responders (FRs) is critical for the safety of personnel and the effectiveness of rescue operations. However, conventional Global Navigation Satellite System (GNSS) technologies are limited in environments where satellite signals are unavailable or severely degraded, such as indoor settings, tunnels, or urban canyons. This Master’s Thesis presents the integration of GNSS-based positioning into an existing prototype designed for first responder tracking, called NavShoe, which employs the FootSLAM algorithm to provide location estimates in GNSS-denied environments. The main objective of incorporating GNSS into the system is to obtain an absolute global position reference, enabling the precise geolocation of the first responder within a global coordinate system. Once GNSS coverage is lost or significantly degraded, the system seamlessly activates the FootSLAM algorithm, which then continues to estimate the responder’s location relatively, using inertial data referenced to the last known GNSS position. This hybrid approach ensures consistent and coherent tracking throughout the entire mission, regardless of environmental conditions. To transmit this critical information in real time to a central operations unit, the system employs LoRa modulation in raw mode. LoRa is particularly well-suited for this application due to its long-range, low-power communication capabilities and its robustness in challenging environments where technologies like WiFi, Bluetooth, ZigBee, or even certain 5G network nodes may fail to operate reliably. One of the key challenges addressed in this project is the limited bandwidth inherent to LoRa communication. To overcome this constraint, a highly efficient byte stream format was developed to encode and transmit positioning data with minimal overhead. Additionally, a custom communication protocol was implemented to manage transitions between GNSS and FootSLAM modes, determine transmission intervals, handle error control, and ensure rapid recovery from spontaneous communication loss. This technology has the potential to significantly enhance situational awareness in mission-critical operations such as firefighting, natural disaster response, underground rescues, special operations, and exploration activities. By continuously monitoring and recording responder trajectories, it improvescoordination and safety, while also offering post-mission analysis capabilities for operational refinement and training.