144 
4.2.6.3 Object recording 
Process 5.3 models the recording of unknown objects during the voyage. These involve either fixed 
non-documented objects (eg wrecks) or mobile objects (foreign vessels). These objects are recorded 
either visually (by way of the on-board sensor technology (RADAR, AIS), or from secondary sources 
(from other vessels/VTS). For the complete description of an unknown object, the following information 
must be determined: 
• “Object identification”: type of object (eg classification of a foreign vessel according to Collision 
Avoidance Regulations), unique characterisation of the object 
• “Object position”: absolute (i.e. position in length and width) or relative (distance and rela 
tive/absolute bearing to own ship) 
• “Object movement”: current movement of the object (absolute/relative speed, absolute/relative 
course): trend forecast as a basis for assessing the encounter situation (eg CPA, TCPA); in 
the case of foreign vessels, the position (“aspect") of the vessel calculated on the own ship (i.e. 
difference in headings). 
Basically a distinction must be made between the receipt of relative object data and absolute object 
data. Relative data are generally received by means of the on-board sensor technology (eg RADAR). 
All recorded movement variables are in this case related to the movement of the own ship, i.e. the ab 
solute movement must be calculated taking into account the state variables of the own ship. This thus 
produces a dependence, of the values determined in this way, upon the accuracy of the state variables 
measured on board. In the case of object recording by means of relative data, moreover, the position 
and identification of the object should be determined in downstream processes (5.3.3., 5.3.4). 
Absolute data are received directly from the observed object (eg via AIS) or from secondary sources 
(e.g. vessel traffic services). In this case, the variables describing the object are directly available. It 
should however be borne in mind that the reliability and accuracy of the values determined in this way 
are dependent on external influences (eg in the case of AIS: dependence on the sensor technology of 
the particular ship). 
The information determined here is stored in a data type “detected object”. This information serves as 
input information for Process 4.1 “Collision avoidance”.