Browsing by Subject "Global Positioning System (GPS)"

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    Real-time Kinematic Positioning: Background, Assessment and Forecasting
    (2018-07) Jackson, John
    This thesis presents an introduction and work performed related to real-time kinematic (RTK) positioning. RTK positioning is a differential positioning method that uses signals from global navigation satellite systems (GNSS). Position solutions using RTK methods have a nominal accuracy on the order of centimeters and are available in real-time, making them useful for such applications as autonomous vehicles and mobile robotics, driver-assist technologies, and precise geospatial data collection. First, a background on positioning using GNSS and RTK methods is presented. Next, an assessment of low-cost RTK receivers for the Minnesota Department of Transportation is described. Several low-cost RTK-capable receivers were assessed using metrics related to accuracy, availability, continuity and ini- tialization in different environments during static and dynamic tests. The low-cost mul- tifrequency receiver tested performed more consistently than the single-frequency low-cost receivers, especially for the dynamic tests. Of the low-cost single frequency receivers, there is a wide range in performance metrics. In addition, a multi-thousand dollar receiver was tested and outperformed all of the low-cost receivers in all environments. Finally, a fore- casting method using recurrent neural networks is explored to increase the robustness of RTK positioning. The methodology presented here was unable to create a reliable RTK solution, but suggestions are offered for future work. The goal of this thesis is to familiarize the reader with the basic premise of RTK positioning and educate them on the capabilities of low-cost receivers.
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    Value of reliability: actual commute experience revealed preference approach.
    (2010-07) Carrion, Carlos
    This research investigates the value placed by travelers on HOT lanes because of improvements in travel time reliability. This value depends on how the travelers regard a route with predictable travel times (or small travel time variability) in comparison to another with unpredictable travel times (or high travel time variability). For this purpose, commuters were recruited and equipped with Global Positioning System (GPS) devices and instructed to commute for two weeks on each of three plausible alternatives between their home in the western suburbs of Minneapolis eastbound to work in downtown or the University of Minnesota: I-394 HOT lanes, I-394 General Purpose lanes (untolled), and signalized arterials close to the I-394 corridor. They were then given the opportunity to travel on their preferred route after experiencing each alternative. This revealed preference data was then analyzed using mixed logit route choice models. Three measures of reliability were explored and incorporated in the estimation of the models: standard deviation (a classical measure in the research literature); shortened right range (typically found in departure time choice models); and interquartile range (75th - 25th percentile). Each of these measures represents distinct ways about how travelers deal with different sections of reliability. In all the models, it was found that reliability was valued highly (and statistically significantly), but differently according to how it was defined. The estimated value of reliability in each of the models indicates that commuters are willing to pay a fee for a reliable route depending on how they value their reliability savings. Furthermore, a meta-analysis is performed in order to explain the differences across valuation ratio estimates across studies. The results indicate differences are significant across regions, choice dimension (e.g. mode choice), travel time unit (e.g. data collected at AM or PM), and year of study.