Efficient DOP Calculation for GPS with and without Altimeter Aiding

Geometric Dilution Of Precision (GDOP) is a factor that describes the effect of geometry on the relationship between measurement error and position determination error. It is used to provide an indication of the quality of the solution. Conventional closed-form GDOP calculation formula applied to all possible combinations of visible satellites is rather time consuming, especially as the number of satellites grows. Approximations, such as the maximum volume method, are faster but optimum selection is not guaranteed. In this paper, a more concise but efficient solution for the calculation of GDOP value in the case of four Global Positioning System (GPS) satellites is firstly reviewed and then extended to cover the other forms of dilution of precision (DOP) values, including vertical DOP (VDOP) and horizontal DOP (HDOP). Secondly, a review and extension of the conventional solution is performed in the case of three GPS satellites aided by an altimeter. Based on the ideas gained from these two approaches, a simpler closed-form DOP formula for three GPS satellites aided by an altimeter is derived. The advantage of the proposed formulation is that it is simpler and thus reduces the computational load in comparison to the conventional one.

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KNOWLEDGE-BASED METHODS FOR OPTIMUM APPROXIMATION OF GEOMETRIC DILUTION OF PRECISION

International Journal of Computational Intelligence and Applications ◽

10.1142/s1469026810002835 ◽

2010 ◽

Vol 09 (02) ◽

pp. 153-170 ◽

Cited By ~ 2

Author(s):

M. R. MOSAVI

Keyword(s):

Measurement Errors ◽

Adaptive Filters ◽

Essential Feature ◽

Positioning System ◽

Dilution Of Precision ◽

Knowledge Based ◽

Gps Satellites ◽

Satellite Geometry ◽

Influence Measurement ◽

Geometric Dilution Of Precision

Global Positioning System (GPS) satellites signal processing to obtain all in view satellite measurements and to use them to find a solution and to do integrity monitoring forms a major component of the load on the receiver's processing element. If processing capability is limited there is restriction on the number of measurements which can be obtained and processed. Alternatively, the number of measurements can be restricted and the resulting saving in load on the processor can be used to offer more spare processing time which can be used for other user specific requirements. Thus if m visible satellites can provide measurements only n measurements can be used (n < m). The arrangement and the number of GPS satellites influence measurement accuracy. Dilution of Precision (DOP) is an index evaluating the arrangement of satellites. Geometric DOP (GDOP) is, in effect, the amplification factor of pseudo-range measurement errors into user errors due to the effect of satellite geometry. The GDOP approximation is an essential feature in determining the performance of a positioning system. In this paper, knowledge-based methods such as neural networks and evolutionary adaptive filters are presented for optimum approximation of GDOP. Without matrix inversion required, the knowledge-based approaches are capable of evaluating all subsets of satellites and hence reduce the computational burden. This would enable the use of a high-integrity navigation solution without the delay required for many matrix inversions. Models validity is verified with test data. The results are highly effective techniques for GDOP approximation.

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Methodology to estimate ionospheric scintillation risk maps and their contribution to position dilution of precision on the ground

Journal of Geodesy ◽

10.1007/s00190-020-01344-0 ◽

2020 ◽

Vol 94 (2) ◽

Cited By ~ 1

Author(s):

Alexandra Koulouri ◽

Nathan D. Smith ◽

Bruno C. Vani ◽

Ville Rimpiläinen ◽

Ivan Astin ◽

...

Keyword(s):

Ionospheric Scintillation ◽

Navigation Systems ◽

End User ◽

Equatorial Anomaly ◽

Dilution Of Precision ◽

Global Positioning ◽

Risk Maps ◽

The Given ◽

Satellite Receiver

Abstract Satellite-based communications, navigation systems and many scientific instruments rely on observations of trans-ionospheric signals. The quality of these signals can be deteriorated by ionospheric scintillation which can have detrimental effects on the mentioned applications. Therefore, monitoring of ionospheric scintillation and quantifying its effect on the ground are of significant interest. In this work, we develop a methodology which estimates the scintillation-induced ionospheric uncertainties in the sky and translates their impact to the end users on the ground. First, by using the risk concept from decision theory and by exploiting the intensity and duration of scintillation events (as measured by the $$S_4$$ S 4 index), we estimate ionospheric risk maps that could readily give an initial impression on the effects of scintillation on the satellite-receiver communication. However, to better understand the influence of scintillation on the positioning accuracy on the ground, we formulate a new weighted dilution of precision (WPDOP) measure that incorporates the ionospheric scintillation risks as weighting factors for the given satellite-receiver constellations. These weights depend implicitly on scintillation intensity and duration thresholds which can be specified by the end user based on the sensitivity of the application, for example. We demonstrate our methodology by using scintillation data from South America and produce ionospheric risk maps which illustrate broad scintillation activity, especially at the equatorial anomaly. Moreover, we construct ground maps of WPDOP over a grid of hypothetical receivers which reveal that ionospheric scintillation can also affect such regions of the continent that are not exactly under the observed ionospheric scintillation structures. Particularly, this is evident in cases when only the global positioning system is available.

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Influence of Ephemeris Error on GPS Single Point Positioning Accuracy

Artificial Satellites ◽

10.2478/arsa-2013-0011 ◽

2013 ◽

Vol 48 (3) ◽

pp. 125-139

Author(s):

Ma Lihua ◽

Meng Wang

Keyword(s):

Global Positioning System ◽

Simulation Analysis ◽

Single Point ◽

Line Of Sight ◽

Positioning System ◽

Gps Satellites ◽

Time Period ◽

Global Positioning ◽

Orbital Position ◽

The Relationship

Abstract The Global Positioning System (GPS) user makes use of the navigation message transmitted from GPS satellites to achieve its location. Because the receiver uses the satellite's location in position calculations, an ephemeris error, a difference between the expected and actual orbital position of a GPS satellite, reduces user accuracy. The influence extent is decided by the precision of broadcast ephemeris from the control station upload. Simulation analysis with the Yuma almanac show that maximum positioning error exists in the case where the ephemeris error is along the line-of-sight (LOS) direction. Meanwhile, the error is dependent on the relationship between the observer and spatial constellation at some time period.

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Temperature distribution in a cigarette oven during baking

Thermal Science ◽

10.2298/tsci1504201z ◽

2015 ◽

Vol 19 (4) ◽

pp. 1201-1204 ◽

Cited By ~ 1

Author(s):

Qing Zhang ◽

Jia-Cun Shao ◽

Hang Zhao ◽

Kai Zhang ◽

Zhong-Di Su

Keyword(s):

Temperature Field ◽

Energy Consumption ◽

Temperature Distribution ◽

Flow Field ◽

Finite Volume Method ◽

Numerical Investigation ◽

Finite Volume ◽

Volume Method ◽

The Relationship

Baking treatment is one of the most important processes of cigarette production, which can significantly enhance quality of tobacco. Theoretical and numerical investigation on temperature distribution in a cigarette oven during baking was carried out. The finite volume method was used to simulate the flow field. The relationship between the uniformity of temperature field and impeller?s speed was given finally, which is helpful to optimize cigarette oven with better quality and less energy consumption.

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