NovAtel CORRECT with Precise Point Positioning (PPP) for High Accuracy Kinematic Applications

A. Jokinen, C. Ellum, I. Webster, S. Masterson and T. Morley

Abstract:	Precision GNSS users are continuously pushing the technology for improved performance that includes better accuracy, operation in more challenging conditions, and the ability to keep working for extended periods of time. The availability of reliable, high quality position solutions to meet these ever increasing demands in variable applications is the heart of NovAtel CORRECT™. There are a large number of applications that benefit from globally available cm-level positioning and, pairing core GNSS technology with corrections delivered by data providers like TerraStar, enables cm-level GNSS positioning in harsher conditions for applications like precision agriculture and mobile mapping. NovAtel CORRECT™ uses both PPP and RTK technologies to provide users with globally or locally available centimeter-level positioning. RTK has been widely used for many years. It enables the rapid acquisition of centimeter-level positions that are suitable for virtually all sky-visible high-precision applications. However, the logistical challenges associated with deploying and using RTK have meant that many applications have not been able to reap the benefits of high-precision positioning. NovAtel CORRECT™ expands the availability of centimeter-level positioning into many of these previously un-served applications. It combines globally valid and distributed corrections with advanced PPP algorithms, and lies near the apex of high-precision positioning technologies. This paper will discuss the recent developments of NovAtel CORRECT™ using the latest TerraStar correction data. From a user’s perceptive, the most important new feature is immediate re-convergence, in which the receiver can recover from short signal outages back to a similar level of position error as before the outage. Under normal conditions, complete signal interruptions of at least 60 seconds can be recovered from. Depending on the ionosphere and other observing conditions, even longer interruptions can be tolerated. This ability to recover quickly from GNSS and correction signal outages translates into increased working time for the user which can reduce downtime and increase overall productivity in any application. The improved kinematic performance of NovAtel CORRECT™ with the latest TerraStar data is demonstrated in this paper using agricultural-application field test data collected in Brazil and Canada. In addition, the initial convergence and final accuracy improvements of the TerraStar service are discussed and demonstrated. The key algorithmic improvement in NovAtel CORRECT™ is the addition of PPP carrier-phase integer ambiguity resolution. Ambiguity resolution is necessary to unlock the full accuracy of carrier-phase positioning. Furthermore, it enables the aforementioned immediate re-convergence. In NovAtel CORRECT™, PPP ambiguity resolution is enabled by the phase bias corrections broadcast by TerraStar. Resolution is carried out in two steps: wide-lane and narrow-lane resolution. In the first step, dual-frequency wide-lane ambiguities are estimated from the Melbourne-Wübbena combination and the ambiguities fixed to integers using the bootstrapping method. In the second step, narrow-lane ambiguities are calculated based on float ionosphere-free ambiguities and fixed wide-lane ambiguities. Narrow-lane ambiguity resolution is done by employing the LAMBDA method and the ambiguities validated using the ratio test.
Published in:	Proceedings of the 28th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2015) September 14 - 18, 2015 Tampa Convention Center Tampa, Florida
Pages:	1123 - 1152
Cite this article:	Jokinen, A., Ellum, C., Webster, I., Masterson, S., Morley, T., "NovAtel CORRECT with Precise Point Positioning (PPP) for High Accuracy Kinematic Applications," Proceedings of the 28th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2015), Tampa, Florida, September 2015, pp. 1123-1152.
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