Browsing by Subject "Accuracy"

Now showing 1 - 6 of 6
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    Accuracy of a Modular GPS/GLONASS Receiver
    (University of Minnesota Duluth, 2018) Joyce, Michael; Moen, Ronald
    One of the main factors that affect GPS location accuracy is the type of GPS receiver being used. In general, more expensive receivers (e.g., mapping-grade or survey-grade receivers) provide better accuracy, and GPS users must balance GPS receiver cost with location accuracy when determining which receiver to use. Applications of GPS often require use of GPS receivers in less than ideal conditions while GPS manufacturers often report accuracy specifications that can be expected under ideal conditions. Forest canopies reduce GPS accuracy by interfering with signal transmission between GPS satellites and the GPS receiver and causing multipath errors. When GPS receivers are to be used in forest conditions and accuracy thresholds must be met, it is important to conduct accuracy testing in forest conditions rather than relying on accuracy specifications provided by the manufacturer. We tested the accuracy of the SXBlue II + GNSS, a modular, mapping-grade GPS receiver, under forest canopies in northeastern Minnesota. We estimated cumulative accuracy to evaluate the relationship between collection period and accuracy. GPS test sites covered a range of canopy conditions. We compared accuracy among sites to determine how canopy closure influenced location accuracy. Finally, we compared post-hoc methods to evaluate accuracy based on characteristics of the sites and acquired GPS fixes. The SXBlue II + GNSS receiver typically provided meter or sub-meter accuracy, even under forest canopy. Maximum accuracy was achieved after 10-30 minutes. Accuracy was lower at sites with higher canopy closure values. In sites with canopy closure >65%, maximum accuracy was reduced to 1.5 m. Post-hoc filtering to remove outliers did not improve accuracy. There was a strong, positive relationship between 50% CEP, a measure of location precision, and accuracy, suggesting that 50% CEP can be used for post-hoc accuracy assessment. Our results suggest that the SXBlue II + GNSS provides sufficient accuracy for a wide range of applications, including those that require GPS location measurement in forest conditions.
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    Accuracy of a Modular GPS/GLONASS Receiver
    (University of Minnesota Duluth, 2018) Joyce, Michael; Moen, Ronald
    One of the main factors that affect GPS location accuracy is the type of GPS receiver being used. In general, more expensive receivers (e.g., mapping-grade or survey-grade receivers) provide better accuracy, and GPS users must balance GPS receiver cost with location accuracy when determining which receiver to use. Applications of GPS often require use of GPS receivers in less than ideal conditions while GPS manufacturers often report accuracy specifications that can be expected under ideal conditions. Forest canopies reduce GPS accuracy by interfering with signal transmission between GPS satellites and the GPS receiver and causing multipath errors. When GPS receivers are to be used in forest conditions and accuracy thresholds must be met, it is important to conduct accuracy testing in forest conditions rather than relying on accuracy specifications provided by the manufacturer. We tested the accuracy of the SXBlue II + GNSS, a modular, mapping-grade GPS receiver, under forest canopies in northeastern Minnesota. We estimated cumulative accuracy to evaluate the relationship between collection period and accuracy. GPS test sites covered a range of canopy conditions. We compared accuracy among sites to determine how canopy closure influenced location accuracy. Finally, we compared post-hoc methods to evaluate accuracy based on characteristics of the sites and acquired GPS fixes. The SXBlue II + GNSS receiver typically provided meter or sub-meter accuracy, even under forest canopy. Maximum accuracy was achieved after 10-30 minutes. Accuracy was lower at sites with higher canopy closure values. In sites with canopy closure >65%, maximum accuracy was reduced to 1.5 m. Post-hoc filtering to remove outliers did not improve accuracy. There was a strong, positive relationship between 50% CEP, a measure of location precision, and accuracy, suggesting that 50% CEP can be used for post-hoc accuracy assessment. Our results suggest that the SXBlue II + GNSS provides sufficient accuracy for a wide range of applications, including those that require GPS location measurement in forest conditions.
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    Assessing the Accuracy and Reliability of Root Crack and Fracture Detection in Teeth Using Sweep Imaging with Fourier Transform (SWIFT) Magnetic Resonance Imaging (MRI)
    (2017-08) Schuurmans, Tyler
    Introduction: Magnetic Resonance Imaging (MRI) has the potential to aid in determining the presence and extent of cracks/fractures in teeth due to more advantageous contrast, without ionizing radiation. An MRI technique called Sweep Imaging with Fourier Transform (SWIFT) has overcome many of the inherent difficulties of conventional MRI with detecting fast-relaxing signals from densely mineralized dental tissues. The objectives of this in vitro investigation were to develop MRI criteria for root crack/fracture identification in teeth and to establish intra- and inter-rater reliabilities and corresponding sensitivity and specificity values for the detection of tooth-root cracks/fractures in SWIFT MRI and limited field of view (FOV) CBCT. Materials and Methods: MRI-based criteria for crack/fracture appearance was developed by an MRI physicist and 6 dentists, including 3 endodontists and 1 Oral and Maxillofacial (OMF) radiologist. Twenty-nine human adult teeth previously extracted following clinical diagnosis by a board-certified endodontist of a root crack/fracture were frequency-matched to 29 non-cracked controls. Crack/fracture status confirmation was performed with magnified visual inspection, transillumination and vital staining. Samples were scanned with two 3D imaging modalities: 1) SWIFT MRI (10 teeth/scan) via a custom oral radiofrequency (RF) coil and a 90cm, 4-T magnet; 2) Limited FOV CBCT (1 tooth/scan) via a Carestream (CS) 9000 (Rochester, NY). Following a training period, a blinded 4-member panel (3 endodontists, 1 OMF radiologist) evaluated the images with a proportion randomly re-tested to establish intra-rater reliability. Overall observer agreement was measured using Cohen’s kappa and levels of agreement judged using the criteria of Landis and Koch. Sensitivity and specificity were computed with 95% confidence interval (CI); statistical significance was set at 0.05. Results: MRI-based crack/fracture criteria were defined as 1-2 sharply-delineated, high-signal (bright/white) line shape(s) that must be visible on multiple contiguous image slices. The line shape(s) must present as: single entities, or parallel pairs in close proximity, or pairs in close proximity exhibiting convergence or divergence extending from the external boundary of the tooth to the pulpal cavity. Intra-rater reliability for MRI was fair-to-almost perfect (κ=0.38-1.00) and for CBCT was moderate-to-almost perfect (κ=0.66-1.00). Inter-rater reliability for MRI was fair (κ=0.21; 95%CI:0.10-0.31; p< 0.001) and for CBCT was moderate (κ=0.45; 95%CI:0.34-0.56; p<0.001). Sensitivity: MRI=0.59 (95% CI:0.39-0.76; p=0.46); CBCT=0.59 (95% CI:0.59-0.76; p=0.46). Specificity: MRI=0.83 (95% CI:0.64-0.94; p<0.01); CBCT=0.90 (95% CI:0.73-0.98; p<0.01). Conclusions: Education and training for both imaging modalities is needed to improve reliabilities for the identification of tooth-root crack/fractures. Despite the advantages of increased contrast and absence of artifact from radio-dense materials in MRI, comparable measures of sensitivity and specificity (in relation to CBCT) suggest quality MRI improvements are needed, specifically in image acquisition and post-processing parameters. Given the early stage of technology development and multiple available pathways to optimize MR imaging of teeth, there may be a use for SWIFT MRI in detecting cracks and fractures in teeth.
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    Development and Demonstration of a Cost-Effective In-Vehicle Lane Departure and Advanced Curve Speed Warning System
    (Minnesota Department of Transportation, 2018-12) Faizan, Muhammad; Hussain, Shah; Hayee, M. I.
    A Lane-Departure Warning System (LDWS) and Advance Curve -Warning System (ACWS) are critical among several Advanced Driver- Assistance Systems (ADAS) functions, having significant potential to reduce crashes. Generally, LDWS us e different image processing or optical s canning techniques to detect a lane departure. Such LDWS have some limitations such as harsh weather or irregular la ne markings can influence their performance. Other LDWS use a GPS receiver with access to digital maps with lane-level resolution to improve the system's efficiency but make the overall system more complex and expensive. In this report, a lane-departure detection method is proposed, which uses a standard GPS receiver to determine the lateral shift of a vehicle by comparing a vehicle’s trajectory to a reference road direction without the need of any digital maps with lane-level resolution. This method only needs road-level information from a standard digital mapping database. Furthermore, the system estimates the road curvature and provides advisory speed for a given curve simultaneously. The field test results show that the proposed system can detect a true lane departure with an accuracy of almost 100%. Although no true lane departure was left undetected, occasional false lane departures were detected about 10% of the time when the vehicle did not actually depart its lane. Furthermore, system always issues the curve warning with an advisory speed at a safe distance well ahead of time.
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    Exploring the Accuracy of School Rankings for Accountability Decisions
    (2023-12) Vue, Yi
    In the U.S., the school accountability system in education uses testing as a major part of its decision-making process. Part of this decision making comes from the result of student test scores, which are aggregated to estimate school scores (typically in the metric of percent proficient). Regarding precision of such school metrics, measurement error is assumed to have a net value of zero across the population of students within a school, but students are not randomly assigned to schools. The aggregation of student scores to obtain school scores retains the measurement error from the students within their respective schools. This study used available data to emulate how one state uses test scores to rank schools and simulated various conditions to examine how the accuracy of the school rankings might be affected.The conditions examined multiple measurement error models to evaluate changes in accuracy based on the various measurement error models. If measurement error has a net value of zero, accuracy should not be affected across this condition. Another condition examined the different methods of aggregating student scores to obtain school scores. If student measurement error is aggregated along with the student score to estimate school scores, some schools may have more error than other schools, and this information may be helpful when making interpretations about school rankings. The last condition was the reliability of the test. Real data summary statistics were used in the study, so the minimum and maximum test reliability was examined regarding how accuracy was affected across the other conditions. Several major takeaways were found. When there was more error variance, the accuracy of school rankings dropped, but changes in the specification of the error distribution did not change the accuracy of school rankings. The biggest association with accuracy of school rankings was how student test scores were aggregated to obtain school scores. The aggregation of student scores condition had the largest difference in accuracy across the conditions, on average. In this study, I hoped to inspire more research to provide validity evidence to support the decision-making process of the accountability system, especially studies that attempt to minimize error within these processes.
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    Predicting intervention effectiveness from oral reading accuracy and rate measures through the learning hierarchy/instructional hierarchy
    (2012-11) Szadokierski, Isadora Elisabeth
    The current study used the Learning Hierarchy/Instructional Hierarchy (LH/IH) to predict intervention effectiveness based on the reading skills of students who are developing reading fluency. Pre-intervention reading accuracy and rate were assessed for 49 second and third grade participants who then participated in a brief experimental analysis (BEA) to determine whether each participant responded best to an acquisition or a proficiency intervention package. Analyses indicate significant baseline differences between students who responded to each intervention package. Moreover, accuracy and rate have a positive correlation with proficiency intervention effectiveness and a negative correlation with acquisition intervention effectiveness. Predictive models and potential accuracy and rate cut scores for making intervention decisions were also investigated.