133 
4.2.6.1.1 Determination of primary state variables 
To increase comprehensibility, the input information of the processes shown in DFD 5.1.1 is not repre 
sented. The processes assembled here exhibit a uniform structure in this respect. Basically, these 
receive values from various sensors, process this using plausibility criteria and additional information 
(e.g. sensor locations), and supply a “system state variable”. In many cases, primary state variables are 
moreover dependent on further variables - as a function of the sensor used - (e.g. speed error or width 
correction for the heading when using a gyro compass). These additional input variables are likewise 
not represented in DFD 5.1.1. It should be noticed that the sensor location represented in the data flow 
diagrams relates to all sensors used in each case. For each sensor, therefore, the particular sensor 
location must be transmitted. 
Within the framework of the task “State identification”, only those variables are considered which de 
scribe the state of the system “ship”. Other values determined by means of the on-board sensor tech 
nology which describe the environment variables (eg wind, air temperature) are assembled in Process 
5.2 “Observation of the environment”. 
All processes to determine state variables possess a uniform structure. In the process “Compare data 
and criteria”, the plausibility of the state variables received is checked. Plausibility testing in this context 
is the checking of the validity (qualitative) and comparison with other independent data suppliers (quan 
titative). Plausibility testing - from the standpoint of the data supplier - thus has an “internal" aspect 
(checking the validity of the own measured data) and an “external” aspect (comparison of the supplied 
datum with other data sources). To assess the “quality” of the transmitted state variable by the “user”, it 
is necessary to transmit the information concerning plausibility, usability and source with the state vari 
able. 
The data flow “Reference model” in DFD 5.1.1.1 (“Determine own ship position”) contains the geodetic 
datum on which the particular position determined is based (geodetic reference system) and the sensor 
location (local reference system). 
In the case of all state variables which contain correction processes, a distinction must be made on 
closer consideration between a “raw value” (sensor value without correction) and a “corrected value”. 
For the variables where according to DIN 13312 “raw values” are defined, these are considered as data 
types (eg KrK, MgK in DFD 5.1.1.2). If no such definition exists (eg for SOGX - see DFD 5.1.1.3), no 
additional data types are introduced.