NorthStar EXPLORER 650 - Page 59

59Northstar Explorer 650 Installation and Operation Manual
NMEA datum offset
If you select a map datum other than WGS 84,
the map datum offset can be applied to latitude
and longitude coordinates sent on the Explorer
NMEA output:
Latitude and longitude coordinates
displayed on any NMEA repeater do not
match the coordinates on the Explorer.
Latitude and longitude coordinates
broadcast on any NMEA VHF transmitter will
be the same as the coordinates on a WGS 84
chart.
Latitude and longitude coordinates
displayed on any NMEA repeaters match
the coordinates on the Explorer. However,
latitude and longitude coordinates broadcast
on any NMEA VHF transmitter will be slightly
offset from coordinates on a WGS 84 chart.
Map shift
Some charts have consistent position errors. To
correct this, apply a map shift. After a map shift:
The positions of cartographic features (such
as land, rocks, buoys and depth contours)
move on the Explorer chart display to where
they should be.
The positions of the boat, waypoints, tracks,
and lines of latitude and longitude on the
Explorer chart display remain unchanged.
Applying a map shift
1 Move the boat to a known point on the chart,
for example a marina berth.
2 In the Chart setup menu, select
Map shift.
3 Move the cursor to the position on the chart
where the boat actually is.
4 Press
and select Set.
5 Press
to set the new map shift.
The boat will now be displayed at its
actual location.
Clearing the map shift
Clearing the map shift removes any map shift
from the cartographic features on the Explorer
chart display.
1 In the Chart setup menu, select
Map shift.
2 Press
and select Clear.
3 Press
.
General submenu
Plotter mode Only scales available on the chart card can be displayed.
If you press or to select a chart scale which is not available, on
the chart card, the chart display will change to this scale but will only display
the boat position and track (if enabled). The rest of the display is white with
black crosshatch lines and no chart information is displayed. This is useful
to zoom to a small scale to track small boat movements or if there is no
detailed chart for an area.
Mixing levels Mixes lower detail charts with higher detail charts on chart boundaries.
:Lower detail chart is not shown.
:Lower detail chart shown; this is slower to redraw.
!
WARNING
When you change to a chart with a different
datum, change the Explorer map datum
again.
!
WARNING
Map shift is for eliminating minor offsets.
It should not be used if the correct datum
is available. Use map shift with caution:
incorrect application will cause incorrect boat
positions.