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1. Operational Overview
1-11
1.8 Geodetic Datum
This chart radar uses ENC material, produced to standards using WGS-84 datum. Positioning devices connected to
this equipment must work in the WGS-84 datum. IMO require that a chart radar must give an alert if the datum of a
positioning device is not the WGS-84. In practice this is impossible, because the standard used by positioning
devices (IEC 61162, previously NMEA 0183) does not include a datum message. Consequently, the classification
societies only approve a positioning device interfaced with the chart radar where datum cannot be changed (i.e., is
always WGS-84).
Note: The ability to check datum of position is a relatively new feature for position receivers. It was introduced in
standard IEC 61162-1 Ed2, published July 2000. Only an EPFS (for example GPS or DGPS) that has "IEC 61162-1
Ed 2 (2000-7)" indicated in its type approval certificate can support the chart radar to detect datum mismatch.
This system allows the user to change viewed datum. This selection of the datum does not change anything inside
the system for navigation calculation processes or for electronic sea chart display processes. But it changes the
numerical values of positions displayed on the chart radar display into the user-chosen datum. This is very useful,
especially if you like to plot positions from the chart radar on a traditional paper chart.
1.9 Navigation Marks on Chart Radar and ECDIS Modes
If the EBL and VRM cannot be controlled from a control unit, use the NAV Marks dialog box. To show this box,
spin the scrollwheel to show ---/Info/Nav Marks in the guidance box then push the right button.
Set 1 page
REF point: Turn on/off the reference point on the electronic chart.
VRM: Turn on/off the VRM (Variable Range Marker), which is displayed around
the reference point.
EBL: Turn on/off EBL (Electronic Bearing Line), which extends from the reference
point.
Rings: Turn on/off the range rings, which circumscribe the reference point. The ring
interval depends on scale of displayed chart.
Info: Turn on/off numerical information about VRM, EBL and reference point. This
item is not displayed in the radar or radar chart mode.
REF point - Centered: Check to set center for your ship.
Set 2 page
Provides a second set of the items contained in set 1.