Integrated StarFire GPS with GLONASS for Real-Time Precise Navigation and Positioning

The integrated StarFire (TM) GPS with GLONASS system was developed and launched by John Deere's NavCom Technology unit to provide precise real time navigation and positioning services for receivers supplied by NavCom and John Deere to their customers and resellers. The paper provides a high level overview of the upgraded StarFire system architecture. Multiple aspects of the system are described, including the GNSS reference receiver network, the communications infrastructure, data processing at the network Processing Centers, the correction distribution mechanism and the steps taken to ensure reliability. The real-time monitoring capability and the user receivers are also described. The core of the upgraded StarFire system is an innovative Clock and Orbit Real-time Estimator (iCORE) which estimates and predicts the orbits and clocks of the GNSS satellites in real time after collecting the measurements from a global network of GNSS reference stations. The performance of the real-time orbits and clocks is compared to IGS final GPS and GLONASS products. The 3D RMS for GPS orbits is below 5cm. The GLONASS constellation is integrated into the StarFire system and an accuracy of about 12cm 3D RMS for GLONASS orbits has been achieved. Using the improved GPS and GLONASS orbit and clock products, the NavCom GNSS receivers, with integrated StarFire L-band signal tracking, can provide improved StarFire navigation by using both GPS and GLONASS satellites in a combined real-time solution. Test results show high accuracy, availability and reliability, both in open sky and in challenging environments, as well as significantly reduced convergence time. The NavCom StarFire GNSS receivers are able to achieve a global RMS accuracy of 5 centimeters horizontal and 10 centimeters vertical in real-time.