Northstar
M121/M84
Installation and Operation Manual
108
Appendix C Glossary and navigation data
Air temp
- Air temperature (requires Northstar
721 VHF radio).
Alarm status
- Shows the symbol (see section
19-10) for each alarm that is on. The symbol
is normally black and turns red if the alarm
triggers.
Attention Area
- An important area on a chart,
such as a restricted anchorage or a shallow area
(see section 19-2).
AIS
- Automatic Identification System. A System
where vessel information (location, course,
speed, etc.) is broadcast by VHF radio, for use
by other vessels in navigation and collision
avoidance.
Bathymetric line
- A depth contour line on
the chart.
Chart card
- A plug-in card that stores chart
data for a region (see section 1-3).
C-MAP
™
chart card
- See Chart card.
C-MAP
™
user card
- See User card.
CPA
- Closest Point of Approach. The closest
distance two vessels will come to each other
based on their current course and speed.
Cursor
- A symbol on the display (see
section 3-2).
DGPS
- Differential Global Positioning System.
A navigation tool based on GPS with some
errors corrected (see section 7).
DSC
- Digital Selective Calling. A feature
of marine radios enabling communication
between specific vessels, as well as distress
alerts.
DTN
- Distance to the next position the
M121/M84 is navigating to, either a waypoint or
the cursor.
Fish forecaster
- An estimate of the likelihood
of catching fish based on barometric pressure.
The more fishes that show the higher the
likelihood (requires Northstar 721 VHF radio).
Gear
- The gear the engine is in (requires
SmartCraft).
Goto
- A simple way of navigating straight to a
waypoint or to the cursor position (see section
3-1).
GPS
- Global Positioning System. A satellite-
based navigation tool (see section 7).
Leg
- The straight segments of a route between
waypoints. A route with four waypoints has
three legs.
MMSI
- Maritime Mobile Service Identity.
Unique identification number for a vessel, for
use in Digital Selective Calling.
MOB
- Man overboard.
MOB function
- Starts navigating back to
the place where someone fell overboard (see
section 2-4).
NavBus
- A way of connecting Northstar
instruments together to share data (see section
20-10).
NMEA
- National Marine Electronics
Association.
NMEA 0183
- A standard for interfacing marine
electronic devices (see section 20-11).
Radar guard zone
- An area around the
boat, set up by the operator and defined by
distance and bearing. If an object (e.g. another
boat) enters the radar guard zone, an alarm is
activated.
Rain clutter
- Heavy rain or snow can cause
interference with the radar image.
Range (radar)
- The distance between the
centre of the radar image and the outer range
ring. The scale is shown in the top left corner of
the radar window.
Range rings
- Concentric circles extending
from your boat (usually at the centre of the
radar window) and used to estimate distances
to objects. The scale is shown in the top left
corner of the radar window.
Route
- Two or more waypoints linked in
sequence to form a course for the boat (see
section 7).
