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3 TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

3 Januszewski J.

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Sources of error in satellite navigation positioning

Januszewski J.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

2017

Vol. 11, no. 3

419--423

An uninterrupted information about the user’s position can be obtained generally from satellite navigation system (SNS). At the time of this writing (January 2017) currently two global SNSs, GPS and GLONASS, are fully operational, two next, also global, Galileo and BeiDou are under construction. In each SNS the accuracy of the user’s position is affected by the three main factors: accuracy of each satellite position, accuracy of pseudorange measurement and satellite geometry. The user’s position error is a function of both the pseudorange error called UERE (User Equivalent Range Error) and user/satellite geometry expressed by right Dilution Of Precision (DOP) coefficient. This error is decomposed into two types of errors: the signal in space ranging error called URE (User Range Error) and the user equipment error UEE. The detailed analyses of URE, UEE, UERE and DOP coefficients, and the changes of DOP coefficients in different days are presented in this paper.

BeiDou and Galileo, Two Global Satellite Navigation Systems in Final Phase of the Construction, Visibility and Geometry

Januszewski J.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

2016

Vol. 10, no. 3

381--387

Spatial segment is one of three segments of each satellite navigation systems (SNS). Nowadays two SNSs, GPS and GLONASS, are fully operational, two next SNSs, BeiDou in China and Galileo in Europe, are in final phase of the construction. In the case of China system this segment will consist of 35 satellites with three types of orbits ? medium (MEO), geostationary (GEO) and inclined geosynchronous (IGSO). As GEO and IGSO satellites can be used in China and Asia-Pacific region only, BeiDou MEO constellation with 27 fully operational satellites will be taken into account in this paper. The orbital planes of the Galileo constellation will be divided in “slots” that contains at least one operational satellite. The Galileo reference constellation has 24 nominal orbital positions or operational slots in MEO homogeneously distributed in 3 orbital planes; i.e. 8 slots equally spaced per plane. As the error of user’s position obtained from both systems depends on geometry factor DOP (Dilution Of Precision) among other things the knowledge of the number of satellites visible by the 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 observer at different latitudes for different Hmin, the percentage of satellites visible above angle H, distributions (in per cent) of satellites azimuths and GDOP coefficient values for different Hmin for BeiDou and Galileo systems at different latitudes are presented in the paper.

Nominal and Real Accuracy of the GPS Position Indicated by Different Maritime Receivers in Different Modes

Januszewski J.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

2014

Vol. 8, no. 1

11--19

Nowadays on the ship’s bridge two or even more GPS receivers are installed. As in the major cases the coordinates of the position obtained from these receivers differ the following questions can be posed – what is the cause of this divergence, which receiver in the first must be taken into account etc. Based on information published in annual GPS and GNSS receiver survey it was estimated the percentage of GPS receivers designed for marine and/or navigation users. The measurements of GPS position based on the four different stationary GPS receivers were realized in the laboratory of Gdynia Maritime University in Poland in the summer 2012. The coordinates of the position of all these receivers were registered at the same time. The measurements in mode 3D were made for different input data, the same for all receivers. The distances between the individual unit’s antenna were considered also. Next measurements in mode 3D also were realized on two ships in different European ports. Additional measurements were made in mode 2D with three receivers for different their’s antenna heights. The results showed that the GPS position accuracy depends on the type of the receiver and its technical parameters particularly.