Datum And Arcs Charts; Difference Between Arcs Chart Local Datum And Positions In Wgs-84 Datum - Furuno FEA-2107 Operator's Manual

9.2

Datum and ARCS Charts

9.2.1 Difference between ARCS chart local datum and positions in
WGS-84 datum
The difference between ARCS chart local datum and WGS-84 datum is known as WGS-84 Shift. For most of the
ARCS charts this is known and the system can do the conversion automatically. For some ARCS chart, however,
this is unknown and the user must define the shift. For some ARCS charts this is partially known and the user is
responsible for defining the shift for the unknown areas of partially known ARCS charts. For further details, see the
paragraph "Specifying user WGS-84 shift" on page 9-9.
Further, see "Use with GPS" in the ARCS Navigator User Guide.
How the state of WGS shift is indicated permanently
No warning appears in the cursor window. The
cursor position is shown in the user-chosen working
datum. (See paragraph 13.3 "Choosing Datum".)
The warning WGS undefi. appears (in red) in the
Cursor window.
The system still operates in the user-chosen working
datum. However, the system is unable to correctly do
the transformation between local paper chart datum
and the user-chosen working datum.
The warning WGS user appears (in red) in the
Cursor window.
The system still operates in the user-chosen working
datum. However, the system uses the user-defined
WGS shift to perform the transformation between
local paper chart datum and the user chosen working
datum.
Checking WGS shift status of current chart
The ARCS chart legend contains a WGS shift status field. (To display the ARCS chart legend, place the cursor in
the Sidebar, confirm that the mouse functions area shows Select Sidebar, push the right mouse button, choose Chart
Legend and then push the thumbwheel.)
9. Raster Chart Material
9-5