User's Manual

Table Of Contents
ED 3100 G 140 / 04 (2011-11)
Operating Instructions
III-3 Permanent Area for Navigation
III Main Applications.fm / 10.11.11
III-37
NACOS Platinum
About Speed Sensors
Speed sensors are treated as part of the CCRS. (See chapter III - 2.1 on page III-16 for details). This
means that the indicated speed data and the speed vector dispayed in the PPI/chart area are valid for
the CCRP sected under "CCRP" on page III-28
There may be several speed sensors connected to the system. One of them is chosen by the system on
startup. In the case of speed sensors which transfer the longitudinal speed only, the drift and set can
be entered manually, because those devices cannot detect the effect of leewayand current. As an alter-
native to selection of a speed sensor, it is also possible to input the speed manually, if necessary. If fixed
ARPA targets are available, the speed can also be determined by Reference Target Tracking. See
chapter 7.13 on page A-78 for details.
The speed sensors also include position sensors which transfer not only the position but also the
speed and course made good. Compared to the present-day state of the art, they generally do not
meet the IMO Performance Standards for SDME (Speed and Distance Measuring Equipment, IMO
resolution MSC.96(72). Therefore, they might not be configured in the system, and so it might not
be possible to select them for speed input.
Two different values for the speed of the ship are displayed:
- STW: Speed through Water
Only the longitunial speed (i.e. the speed in ship´s direction) is indicated behind STW. An arrowhead
describes the ahead or astern velocity. The speed through water results in a speed vector described
by CTW, STW. The speed through water often is not equal to the speed over ground, set and drift
may influence the measurement. Speed logs for waterspeed (single axis log) often do only measure
the longitudinal speed, i.e. the speed mainly produced by the propulsion of the ship. In this case
the CTW is equivalent to the actual heading.
The resulting velocity is also indicated as a CTW/STW vector on the HMI and graphically in the PPI/
chart area.
- SOG: Speed over Ground
The speed over ground is the most accurate and best way to determine the ship´s speed. It is often
measured by two-axis logs, doppler-logs or alternatively by position sensors which calculate the
ship´s speed from the difference of positions and the time elapsed while sailing.
The resulting velocity is indicated as a COG/SOG vector on the HMI and graphically in the PPI/chart
area.
It must be ensured that an approved SDME (Speed and Distance Measuring
Equipment) is connected, that means that all speed sensors must accord to IEC
62388 (2007) and to IMO resolution MSC.96(72).