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-47
NACOS Platinum
Position Adjust
For various reasons, it can happen that the position of the electronic chart on the screen is not in agree-
ment with reality (i.e. with the ship's own position and with the radar or ARPA targets). In such cases,
the Position Adjust function offers the possibility of adding the necessary correction value to the
system position used in the NACOS.
Position Adjust is used to correct a constant position-error (position offset) of the selected position sensor
or of a manually set position in Manual DR mode.
Position Offset
If the displayed LAT/LON position is incorrect, the videos and the target symbols of fixed point-targets
(e.g. buoys or landmarks) do not coincide with the chart symbols of these targets or with the user made
symbols that are entered at the correct positions in the chart.
A position offset of the position sensor can also be made visible without displaying the chart background
on a radar, if you observe the coincidence of AIS target symbols with their target videos:
- If all targets have an offset in the same N/E direction, a position error is very probable.
- If all targets have the same bearing offset, it is more probable that either the radar itself or the
compass system needs to be adjusted.
Correction by Position Adjust
The position error can be corrected manually by making the video or symbol of a fixed target coincide
with its chart symbol:
1. Switch on a sufficiently small display range to be able to observe and measure the position offset.
If no radar targets are available as a reference use other means to determine the position error.
2. Click on the Adjust button in the Position display. In the input dialog which then opens, key in the
North and East values of the offset you want to eliminate. South and West values must be set as
negative values.
Note: If the chart object is located north / east of the relevant radar target you must key in a North /
East value and vice versa. With other words: you must shift the chart object to the radar or ARPA target.
3. Clicking on Set in the input dialog takes over the offset value
1)
.
4. As a result, the correction values displayed in the Adjust dialog take effect as a position offset and
this offset is added to the position data of the sensor.
The Position Adjust function must be used extremely carefully! An offset is added
to the received position data, which will have an impact on all NACOS applications
based on or using position data!
The position offset has an effect throughout the whole system, i.e. also on the
automatic track keeping. For this reason, it can happen that, as a result of the
position adjust, an alarm message (e.g. the TP Track Limit alarm of the TRACK-
PILOT) is triggered on connected units and that the Trackpilot takes corrective
actions to steer back to the pre-planned track line
1)
.
1)
If this shall be avoided, switch the TRACKPILOT into Heading or Course mode before you apply a
position offset to the system position.
1)
1) Click on Cancel if you want to discard all inputs