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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.

Availability of the certain value of position error in the navigational systems – model application

Specht C.

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

2007

Vol. 1, no. 4

365--368

The distributions and parameters of the random variable (density functions, distribution functions, expected values, variances, moments etc.), which in navigation is represented by position error, are well defined. This approach is similar like in geodesy, where passing time hasn’t any impact on statistical solution. Presented paper evaluates alternative approach to position error analyses, where the random values are: working and failures times of the system. Arbitrary accepted certain value of position error was assumed as a decision criterion of the system for working state definition. The general mathematical model of the availability of certain value of position error is presented and the special case – exponential distributions of lifetimes and failure times model – was also analysed. The model was adopted for positioning based on EGNOS system measurements and some results are present.