35

Designation

Abbreviation

Dependent  on  state
variables

Further  input  information ­


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  framework ­
  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.