Browsing by Subject "Murrian"
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Item A Dense Reference Network for Mass-Market Centimeter-Accurate Positioning(2016-04) Murrian, Matthew J.; Gonzalez, Collin W.; Humphreys, Todd E.; Novlan, Thomas D.The quality of atmospheric corrections provided by a dense reference network for centimeter-accurate carrierphase differential GNSS (CDGNSS) positioning is investigated. A dense reference network (less than 20 km inter-station distance) offers significant benefits for mass-market users, enabling lowcost (including single-frequency) CDGNSS positioning with rapid integer ambiguity resolution. Precise positioning on a massmarket platform would significantly influence the world economy, ushering in a host of consumer-focused applications such as globally-registered augmented and virtual reality and improved all-weather safety and efficiency for intelligent transportation systems, applications which have so far been hampered by the several-meter-level errors in standard GNSS positioning. This contribution examines CDGNSS integer ambiguity resolution performance in terms of network correction uncertainty, and network correction uncertainty, in turn, in terms of network density. It considers the total error in network corrections: a sum of ionospheric, tropospheric, and reference station multipath components. The paper’s primary goal is to identify the network density beyond which mass-market users would see no further significant improvement in ambiguity resolution performance. It finishes by describing development and deployment of a low-cost dense reference network in Austin, Texas.Item Dense RTK: Mass-Market Positioning for Automated Vehicles(2016-09-15) Humphreys, Todd E.; Pesyna, Ken; Shepard, Daniel; Murrian, Matthew; Kerns, AndrewItem Low-Cost Precise Urban Positioning(2016-09-14) Humphreys, Todd; Pesyna, Ken; Shepard, Daniel; Murrian, Matthew; Kerns, AndrewItem On the Feasibility of cm-Accurate Positioning via a Smartphone’s Antenna and GNSS Chip(2016-04) Humphreys, Todd E.; Murrian, Matthew; Pesyna, Kenneth M. Jr; Sergei Podshivalov, Frank van DiggelenThe feasibility of centimeter-accurate carrier-phase differential GNSS (CDGNSS) positioning using a smartphone’s internal GNSS antenna and GNSS chip is investigated. Precise positioning on a mass-market platform would significantly influence the world economy, ushering in a host of consumer-focused applications that have so far been hampered by the several-meter-level errors in traditional GNSS positioning. Previous work has shown that GNSS signals received through a mass-market smartphone’s GNSS antenna can be processed to yield a centimeter-accurate CDGNSS position solution, but this earlier work processed all GNSS signals externally to the smartphone. The question remains whether a smartphone’s internal oscillator and GNSS chip can produce observables of sufficient quality to support centimeteraccurate carrier-phase-based positioning. This paper answers the question by accessing and processing the raw code- and carrierphase observables produced by a mass-market smartphone GNSS chip—observables that have heretofore been unavailable to the research community. The phone’s carrier phase measurements are shown to suffer from five anomalies compared to those from a survey-grade GNSS receiver, four of which are readily fixed in post-processing. The remaining anomaly, an error in the phase measurement that grows approximately linearly with time, currently prevents the phone’s phase measurements from satisfying the conditions for CDGNSS positioning. But the phone’s measurements seem otherwise fully capable of supporting cmaccurate carrier-phase differential GNSS positioning. A separate analysis of a smartphone’s GNSS signal strength dependency on azimuth and elevation reveals that multipath-induced deep fading and large phase errors remain a significant challenge for centimeter-accurate smartphone positioning.