35 
Designation 
Abbreviation 
Dependent on state 
variables 
Further input in 
formation 
Depth below keel at reference 
DEPTHo 
Zs 
drght z 
Depth below keel at x 
DEPTHx 
zs 
drght z 
Ps 
XsPoint 
Relative humidity 
RHUM 
hAbs 
temper 
Relative wind direction 
RWD 
Wxrel 
Wyrel 
Relative wind speed 
RWS 
Wxret 
Wyrel 
Absolute humidity 
THUM 
hAbs 
True wind direction 
TWD 
X’b 
ys 
Yb 
Wxrei 
Wyrel 
True wind speed 
TWS 
x’b 
/b 
Yb 
Wxrei 
Wyrel 
Water temperature 
WTEMP 
tempwater 
Table 3: Definition of the state variables used in the INS 
4.1.3 Identifying the ship’s characteristic 2 sensors and their output variables 
Criteria for classification of the various sensors are: 
1. The data type which is supplied by the particular sensor 
2. The physical effect which is used in order to determine the particular datum. 
As a result of classification of sensors on the basis of the particular physical effect used, it is possible to 
identify “sensor types” irrespective of the particular concrete technical construction. Within the frame 
work of functional analysis, input data are obtained on the basis of the following physical effects (Table 
4): 
2 The term “characteristic” in this context is understood to mean the sensor functionality to determine the measured 
values. Normally, downstream functions which calculate variables derived from the measured values (eg ROT 
from the differentiation of the HDG) are considered separately.