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Let us prepare the officer of the watch on jamming and spoofing

Felski A.

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

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2019

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Vol. 13. no. 4

847--851

EN

The general accessibility and high accuracy of GPS caused that for a dozen or so years it is applied commonly, not only in marine navigation. We can ascertain that in this regard there exists the monopoly. However, now it is apparently that this system can be easily disturbed, what testify numerous reports. The problem has been treated as troubles in land navigation, however nowadays became every-day reality on coastal waters as well, especially on the Mediterranean and Black Seas and Persian Gulf. Officers who survived this tell that the first impulse in such situation is to verify GPS receiver, regardless of the situation around the ship. The concentration of the officer’s attention on the GPS receiver, especially on coastal waters creates the threat for the ship, however in this situation appear other threats which many officers does not associate with GPS. Usually on the present ship GPS receiver is not only the source of positioning information. It is a source of information for many other devices, so inappropriate work of it generates problems with many other processes on the ship. Today question is who on the bridge can notice GPS problems and how? There are receivers which do not inform about the problem, or present not realistic data. Sometimes only ECDIS picture shows some abnormality, for example still the same position while ship is under the way. On the paper the analysis of possibly aspects of the problem is discussed. Presented analysis goes to the conclusion that should be prepared some procedure how to proceed in case of the lack of GPS signals, as well as the watch officer should be prepared to act in such situation. This is a task for marine academies.

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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

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2014

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Vol. 8, no. 1

11--19

EN

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.

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A Matlab Implementation of Differential GPS for Low-cost GPS Receivers

Ali Q, Montenegro S.

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

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2014

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Vol. 8, no. 3

343--350

EN

A number of public codes exist for GPS positioning and baseline determination in off-line mode. However, no software code exists for DGPS exploiting correction factors at base stations, without relying on double difference information. In order to accomplish it, a methodology is introduced in MATLAB environment for DGPS using C/A pseudoranges on single frequency L1 only to make it feasible for low-cost GPS receivers. Our base station is at accurately surveyed reference point. Pseudoranges and geometric ranges are compared at base station to compute the correction factors. These correction factors are then handed over to rover for all valid satellites observed during an epoch. The rover takes it into account for its own true position determination for corresponding epoch. In order to validate the proposed algorithm, our rover is also placed at a pre-determined location. The proposed code is an appropriate and simple to use tool for post-processing of GPS raw data for accurate position determination of a rover e.g. Unmanned Aerial Vehicle during post-mission analysis.