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Ability to test shipboard automatic identification system instability and inaccuracy on simulation devices

Wawruch R.

Zeszyty Naukowe Akademii Morskiej w Szczecinie

2017

nr 52 (124)

128--134

According to the International Maritime Organisation (IMO) recommendation, when the target data from the automatic identification system (AIS) and radar tracking are both available and the association criteria are fulfilled such that the AIS and radar information are considered for one physical target, then as a default condition of radar equipment, the AIS target symbol and the alphanumerical AIS target data, including information on the closest point of approach (CPA) and time needed to reach the CPA (TCPA) should be automatically selected and displayed as this is more accurate than radar tracking data as the current values of true and relative vectors of a manoeuvring object can be presented without time delay which is characteristic for radar tracking. Research conducted at sea on two ships using real navigational equipment has shown that sometimes onboard AIS presents CPA of other vessels equipped with this device as unstable and inaccurate as the automatic radar plotting aid (ARPA). The source of these instabilities and inaccuracies is to be discovered and thus implemented into radar-navigational simulators used for radar training at operational and management levels. This article briefly describes the encountered inaccuracy and instability of the values of the CPA of the encountered vessel presented by AIS, on current shipboard systems, and the possibilities of their demonstration on simulation devices.

An assessment of ship encounter situations based on predicted points of collision

Galor W.

Zeszyty Naukowe Akademii Morskiej w Szczecinie

2016

nr 46 (118)

82--87

A number of factors affect the safety of navigation, the collision of two ships being one of them. In ship encounter situations, certain principles of behaviour set forth by regulations are in force. Traditionally, a navigational situation is evaluated by identifying the closest point of approach for the passing ships and by comparing it with the assumed safe distance. Then it is necessary to use technical aids: radar and Arpa (depending on the regulations). In Arpa, navigational situation information is mainly presented in the form of vectors. The other presentation that can be used in an encounter situation is the predicted point of collision (PPC). This is the point or points toward which one’s own ship should steer at her present speed (assuming that the target does not manoeuvre) in order for a collision to occur. This paper presents original results of a study into the assessment of ship encounter situations based on PPC. The methods (analytical and graphical) of PPC as a set of circles are elaborated and an analysis of a ship encounter situation performed.