NorthStar GM1708 961X Installation Manual page 41

SECTION TWO - Installation
and doesn't consider atmospheric conditions, Selective Availability, and
signal interference, all of which affect accuracy. HDOP can range from an
ideal value of slightly less than one, up to a poor value of 10 or more; any
value less than two indicates excellent performance.
Lat/lon coordinates
On the CHART screen INFO BARS, the 961 displays lat/lon as degrees,
minutes, and thousandths of minutes. To display this data, press the INFO
key several times. After press the first INFO key, a second INFO key is dis-
played, letting you display additional data on the second INFO BAR.
SOG and COG
You can display SOG and COG in the INFO BAR on the CHART screen, or
on the 3-D STEER screen or numeric STEER screen. To display SOG and
COG on either the STEER or 3-D STEER screens, press the STEER key
once or twice.
SOG and COG readings result from ongoing measurements derived from
the satellite signals; SOG speed is updated every second. You can set the
961 to display its SOG and COG readings more smoothly by setting the
GPS speed averaging value up to 10 seconds. Increasing this averaging
time, however, may reduce overall reaction time. For more details about
GPS speed averaging value, see Chapter 14 in the Northstar 961 Opera-
tions and Reference Manual (GM1700).
Loran-C TDs
The 961 also calculates Loran-C TDs from the GPS coordinates, and dis-
plays them on the CHART-screen INFO BARs. For more details, see "View-
ing loran TDs" in Chapter 5 of the Northstar 961 Operations and Reference
Manual (GM1700).
If you don't touch any key on the control head for one hour or more, its
About
LCD screen automatically dims to about half its normal brightness (based
auto-dimming
on its current brightness), if required by the system. Pressing any key at
mode
any time automatically restores the display's previous brightness level.
This function helps maintain the integrity of the display screen and
reduce power consumption when the 961 is on for many hours at a time.
It is still recommended, however that you keep the lighting level lower
when you don't actually need it.
Turning the unit The procedure for turning off a system with two control heads is slightly
different than turning off a system with one head.
off
To turn off an entire system (both the head and the processor) with one
control head:
961 INSTALLATION MANUAL Revision A Page 31