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Open access

Jacek Januszewski

Vertical Component of Satellite Navigation Systems

The altitude is one of four coordinates of the user's position obtained from Satellite Navigation System (SNS) measurements. The distributions (in per cent) of VDOP coefficient value for different constellations of three SNS - GPS, GLONASS and Galileo - for different masking elevation angles for different user's latitudes are presented in the paper. The results of the measurements of GPS position and vertical accuracy in mode "3D" and position accuracy in mode "2D" for different GPS receivers and different receiver's antenna heights are demonstrated also. Additionally the use of vertical component of SNS in maritime navigation like the determination highly accurate sea-floor depths is presented.

Open access

Jacek Januszewski

Visibility and Geometry of Glonass Constellation

Nowadays there are two worldwide satellite navigation systems - American GPS, fully operational and Russian GLONASS, no fully operational. The number of GLONASS satellites is less than nominal 24; in June 2009 spatial segment consists of 20 satellites, 18 operational and 2 in maintenance. The number of GLONASS satellites visible in open and restricted area, the distributions (in per cent) of the Geometric Dilution of Precision (GDOP) coefficient values and No Fix (without 3D position) for different numbers of GLONASS satellites (interval [18, 24]), for different masking elevation angles (interval [0°, 25°]) at different observer's latitudes (9 zones, each 10° wide), latitude of Poland (zone 50°-60°), in particular, are demonstrated in the paper. Additionally the detailed distributions of satellite azimuths (8 intervals, each 45° wide) and the percentage of satellite visible in open area above given angle at different latitudes for different numbers of satellites are showed. The knowledge of all these distributions are very important, especially after the publication of the U. S. Government report in which we can read that in 2010 the overall GPS constellation will fall below the number of satellites required the actual level of GPS position fix accuracy.

Open access

Jacek Januszewski

The Problem of Compatibility and Interoperability of Satellite Navigation Systems in Computation of User's Position

Actually (June 2011) more than 60 operational GPS and GLONASS (Satellite Navigation Systems - SNS), EGNOS, MSAS and WAAS (Satellite Based Augmentation Systems - SBAS) satellites are in orbits transmitting a variety of signals on multiple frequencies. All these satellite signals and different services designed for the users must be compatible and open signals and services should also be interoperable to the maximum extent possible. Interoperability definition addresses signal, system time and geodetic reference frame considerations. The part of compatibility and interoperability of all these systems and additionally several systems under construction as Compass, Galileo, GAGAN, SDCM or QZSS in computation user's position is presented in this paper. Three parameters - signal in space, system time and coordinate reference frame were taken into account in particular.

Open access

Jacek Januszewski

Abstract

The European Space Agency (ESA) confirmed that it plans to declare an Initial Operational Capability (IOC) once a constellation of 18 satellites is achieved in 2014 and after few Soyuz and Ariane launches Full Operational Capability (FOC) once a constellation of 26 satellites next year or later. In the paper are presented the distribution of the number of satellites visible by the observer and the distribution of GDOP coefficient values both for different masking elevation angles (Hmin) at different observer’s latitudes for three constellations, with 18, 22 and 26 satellites, the distribution of satellite azimuths in open area and the percentage of satellites visible above given angle. Additionally for latitude of Poland (zone 50-60°) No Fix (in per cent) and the detailed distribution of GDOP values for six angles Hmin for all these constellations and the results of other calculations are showed. Finally the results concern the possibility of the positioning and its accuracy for different numbers of Galileo satellites at different observer’s latitudes

Open access

Jacek Januszewski

Combined Constellations GPS and Galileo Systems

As for the users of satellite navigation systems the actual slogan is GPS and Galileo the advantages and disadvantages of different combined constellations of these systems must be taken into account. The distributions (in per cent) of the numbers of satellites visible by the observer at different latitudes situated in open and restricted (urban canyon) area for different masking elevation angles (Hmin) for two combined constellations GPS + Galileo systems (I - 29 GPS satellites + 27 Galileo satellites, II - 29 GPS + 30 Galileo) are presented in this paper. In addition to it the detailed distributions for the observer at latitudes 50-60o for other constellations & elevation angles are demonstrated.

For the first constellation the difference between the number of GPS satellites visible by the observer above horizon (Hmin = 0o) at latitudes 50-60o and the number of Galileo satellites visible by the same observer at the same time can be equal each number between plus 7 and minus 7. This fact must be taken into account in the production and the determination of the number of channel of GPS-Galileo integrated receivers.

Open access

Jacek Januszewski

Abstract

Since many years the coordinates of the position can be obtained with the use of satellite navigation and augmentation systems, SNS and SBAS, respectively. All these systems are called GNSS (Global Navigation Satellite Systems). The main task of the user segment is to transform the products delivered by the GNSS infrastructure into services that users are mainly interested in. That's why GNSS receiver selection depends on user application. Nowadays several hundred different receivers provided by more than one hundred manufacturers are available on the world market. The review of the performance parameters of GNSS receivers accessible in 2014 and last three years is presented in this paper. Additionally the paper gives the reply to some important questions as: for how many applications the given model is destined, which is the percentage of the receivers designed for marine and navigation users, which equipment features of the receiver are the most important for given application, which satellite signals apart from GPS signals can be tracked in the receiver?

Open access

Jacek Januszewski

Abstract

Nowadays (November 2015) there are two global fully operational satellite navigation systems, American GPS and Russian GLONASS. Two next are under construction, Galileo in Europe and BeiDou in China. As the error of observer’s position obtained from these systems depends on geometry factor DOP (Dilution Of Precision) among other things the knowledge of the number of satellites visible by this observer above given masking elevation angle Hmin and the distributions of DOP coefficient values, GDOP in particular, is very important. The lowest and the greatest number of satellites visible in open area by the observer at different latitudes for different Hmin, the percentage of satellites visible above angle H (9 intervals, each 10O wide), distributions (in per cent) of satellites azimuths (8 intervals, each 45O wide) and GDOP coefficient values (8 intervals) for Hmin = 5O for all these four systems at different observer’s latitudes (9 intervals, each wide 10O wide) are presented in the paper. Additionally the lowest elevation for which the number of satellites visible at different latitudes by the observer in open area above this angle is equal 4 or 3 and the distributions (in per cent) of GDOP coefficient values for different Hmin at observer’s latitudes 50-60O for the same four systems are showed. All calculations were made for constellation of GPS 27 satellites, GLONASS 24, Galileo 30 and BeiDou 27 MEO satellites.

Open access

Jacek Januszewski

Abstract

Since few years the significance of the navigation at high latitudes (60° and more), increases incessantly, e.g. northern passages between Atlantic and Pacific Waters. In these regions the user’s position can be obtained mainly from global satellite navigation systems (SNS). Nowadays (September 2016) two systems, American GPS and Russian GLONASS, are fully operational, two next, Galileo in Europe and BeiDou in China, are under construction. As the error of user’s position obtained from these systems depends on geometry factor DOP (Dilution Of Precision) among other things the knowledge of the number of satellites visible by this user above given masking elevation angle Hmin and the distributions of DOP coefficient values, GDOP in particular, is very important. The lowest and the greatest number of satellites visible in open area by the user at high latitudes for different Hmin, the percentage of satellites visible above angle H, distributions of satellites azimuths and GDOP coefficient values for different Hmin for all these four SNSs at different user’s latitudes (beginning from 60°) and other distributions are presented in the paper. All calculations were made for constellation of BeiDou 27 MEO satellites, Galileo 24 satellites, GLONASS 24 and GPS 31 satellites.