Browsing by Author "Saborio, Ricardo"

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    Characterizing Phase-Center Motion of GNSS Antennas Used in High-Accuracy Positioning
    (Center for Transportation Studies, University of Minnesota, 2019-06) Dave, Aditya; Saborio, Ricardo; Sun, Kerry; Sainati, Robert; Gebre-Egziaher, Demoz; Franklin, Rhonda
    Emerging transportation applications require positioning solutions with accuracy of a few centimeters. Current Global Navigation Satellite Systems (GNSS), such as GPS, GLONASS, and Galileo are, in some instances, capable of providing this level of accuracy. Real-Time Kinematic (RTK) techniques can generate solutions accurate to a few centimeters in a given locale. Precise Point Positioning (PPP) techniques promise to deliver RTK-level performance on a global scale. Even though low-cost, RTK-capable GNSS receivers are available today, antennas are a key component affecting quality of the positioning solution. Unless coupled with a high-quality (thus, more expensive) antenna, a low-cost receiver may not provide the centimeter-level accuracy needed for a safety-critical transportation application (e.g., autonomous vehicle, driver assist systems, etc.). Stability of the antenna phase-center is dependent on the antenna quality and can potentially move on the order of tens of mm if not centimeters. The purpose of the work reported here was to characterize the nature of this motion as a function of antenna quality. Anechoic chamber tests were performed using one high-cost and another low-cost GNSS antenna. The selected antennas represented “book ends” on the cost spectrum. These experiments showed that phase-center motion on the low-cost antenna can be a factor of four times larger than on high-quality antennas. Since anechoic chamber tests are not practical for each antenna installation in transportation applications, methods for antenna-specific, in-situ, phase-center motion calibration (modelling) methods have been suggested. Preliminary results suggested efficacy of these in-situ methods.
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    Evaluation of Low-Cost, Centimeter-Level Accuracy OEM GNSS Receivers
    (Minnesota Department of Transportation, 2018-02) Jackson, John; Saborio, Ricardo; Ghazanfar, Syed Anas; Gebre-Egziabher, Demoz; Davis, Brian
    This report discusses the results of a study to quantify the performance of low-cost, centimeter-level accurate Global Navigation Satellite Systems (GNSS) receivers that have appeared on the market in the last few years. Centimeter-level accuracy is achieved using a complex algorithm known as real-time kinematic (RTK) processing. It involves processing correction data from a ground network of GNSS receivers in addition to the signals transmitted by the GNSS satellites. This makes RTK-capable receivers costly (in excess of $10,000) and bulky, making them unsuitable for cost- and size-sensitive transportation applications (e.g., driver assist systems in vehicles). If inexpensive GNSS receivers capable of generating a position solution with centimeter accuracy were widely available, they would push the GNSS revolution in ground transportation even further as an enabler of safety enhancements such as ubiquitous lane-departure warning systems and enhanced stability-control systems. Recently manufacturers have been advertising the availability of low-cost (< $1,000) RTK-capable receivers. The work described in this report provides an independent performance assessment of these receivers relative to high-end (and costly) receivers in realistic settings encountered in transportation applications.