Engineering topics
Sparks, L.
Publications and source records attributed to Sparks, L..
Extreme ionospheric storms and their impact on WAAS
Satellite-based augmentation systems (SBAS) in the absence of selective availability, the ionosphere represents the largest source of positioning error for single-frequency users of the Global Positioning System (GPS).
Estimating SBAS ionospheric delays without grids: the conical domain approach
This paper presents an alternative model of slant delay measurements that allows direct computation of the user's slant delay estimate without the intervening use of a vertical delay grid.
On the ionospheric impact of recent storm events on satellite-based augmentation systems in middle and low-lattitude sectors
In this paper, we use GPS measurements of geomagnetic storm days to perform a quantitative assessment of WAAS-type ionospheric correction algorithms in other parts of the world such as the low-latitude Brazil and mid-latitude Europe.
An assessment and comparison of WAAS ionosheric correction algorithms in CONUS and Europe
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Characterizing the dependence of satellite-based augmentation systems upon the spatial distribution of GPS measurements
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Alternative ionospheric correction algorithms for satellite-based augmentation systems in low-latitude region
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An alternative ionospheric correction algorithm for satellite-based augmentation systems in low-latitude region
In this paper, we use data from the South American region to perform a quantitative assessment of WAAS-type ionospheric correction algorithms in this region.
Characterizing the dependence of satellite-based augmentation systems upon the spatial distribution of GPS measurements
This paper presents a method for characterizing in terms of a scalar metric the degree which a given spatial region is sampled densely and uniformly by a given set of GPS measurements.
The dependence of WAAS ionospheric error bounds upon the spatial distribution of GPS measurements
This paper examines the dependence of the threat model upon the spatial distribution of GPS measurements.
The conical fit approach to modeling ionospheric total electron content
The Global Positioning System (GPS) can be used to measure the integrated electron density along raypaths between satellites and receivers. Such measurements may, in turn, be used to construct regional and global maps of the ionospheric total electron content (TEC). Maps are generated by fitting measurements to an assumed ionospheric model.
Large-scale ionospheric disturbances during the April 2002 storms
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An assessment of the current WAAS algorithm in the South American region
In this paper, we use a network of 230 GPS receivers worldwide, each equipped with dual-frequency GPS receivers. We assessed the WAAS's planar fit algorithm in the equatorial region where the spatial gradients and the absolute slant TEC are known to be the highest in the world.
Sudden ionospheric delay decorrelation and its impact on WAAS
In the absence of selective availability, the ionosphere represents the largest source of positioning error for single-frequency users of the GPS. In differential GPS systems such as the Wide Angle Augmentation System, vertical ionospheric delays are modeled at regularly-spaced intervals in latitude and longitude. The broadcast bound on the error at each of these points is designated the grid ionospheric vertical erorr (GIVE). A critical integrity requirement of WAAS is that the broadcast GIVE bounds residual error with a very high degree of confidence.
Sudden ionospheric delay decorrelation and its impact on WAAS
We report a methodology for assessing the impact on WAAS posed by a sudden increase in the level of ionospheric disturbance. The methodology is based upon the forming an estimate of the probability P(D) that a WAAS user will confront a sudden increase in the level of ionospheric disturbance following a period of relative calm. By restricting the tabulation of fit residuals to only those fits where the spatial coverage of the fit points is sufficiently good, we have determined a limiting upper bound of P(D) to be 2x10(sup -6).
The WAAS ionospheric threat model
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Assessing the threat of undersampled ionospheric irregularities for wide area differential GPS systems
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Assessing the threat of undersampled ionospheric irregularities for wide area differential GPS systems
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