The noise term of GPS phase data can be calculated from the measured carrier-to-noise power density ratios (C/NO). The C/NO values are used in the proposed SIGMA-s model to calculate the variance matrix of double-differenced GPS phase data. Examples show the capability of this model to yield higher accuracies for GPS surveys than the use of the standard weighting scheme. Most importantly, the SIGMA-e model allows the use of noisier phase data from very low elevation satellites to overcome poor satellite geometry problems.
Convergence across the Java Trench has been estimated for the first time, from annual Global Positioning System (GPS) measurements commencing in 1989. The directions of motion of Christmas and Cocos Islands are within 1° of that predicted by the No‐Net Rotation (NNR) NUVEL‐1 plate motion model for the Australian plate although their rates are 25% and 37% less than predicted, respectively. The motion of West Java differs significantly from the NNR NUVEL‐1 prediction for the Eurasian plate with a 21° difference in direction and a 40% increase in rate. We infer that either West Java moves with a distinct Southeast Asian plate or this region experiences plate margin deformation. The convergence of Christmas Island with respect to West Java is 67±7 mm/yr in a direction N11°E ± 4° which is orthogonal to the trench. The magnitude of convergence agrees with the rescaled NUVEL‐1 relative plate model which predicts a value of 71 mm/yr between Australia and Eurasia. The direction of motion matches the direction inferred from earthquake slip vectors at the trench but may be more northerly than the N20°E±3° predicted by NUVEL‐1. On June 2, 1994, almost a year after the last GPS survey, an Mw=7.5 earthquake with slip vector direction N5°E occurred south of central Java.
Least-squares estimation (LS) yields results of low accuracy in the presence of GPS phase-corrupting environmental conditions. We present a robust estimator that clearly identifies outlying observations caused by obstacles like diagonal cables, branches, or leaves. It performs significantly better than standard LS and signal-to-noise ratio dependent weighting if unfavorable signal distortion occurs, and is equal to LS otherwise. The estimator is realized by an iterated LS algorithm using an equivalent weight matrix. It is a generalization of the Danish Method to heterogeneous and correlated observations. The excellent performance of the estimator for processing short static sessions is demonstrated using data obtained from an investigation of GPS signal obstruction.
This study compared three-dimensional release parameters and important features of the throwing technique for male javelin throwers of three different skill levels (elite, club, novice), recorded using three-dimensional cine or video. As expected, significant differences (p < .01) in throw distances and release speeds were found between all three groups. The only other release parameter for which a significant difference was found (between club and novice groups) was the yaw angle. The increase in release speed with increasing skill across the groups may be attributable in part to greater run-up speeds. Also important were significantly greater peak speeds of the throwing shoulder, elbow, and hand during the delivery stride for the elite group compared to the other groups. Significantly longer acceleration paths at the start of the delivery stride and a delay in elbow flexion until after final foot strike for the elite throwers were also important in generating greater release speeds.
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