Using Gps To Determine Position - NorthStar 961X Operation And Reference Manual

Chapter 5 - Understanding Position Coordinates

Using GPS to determine position

Lat/lon coordinates
SOG and COG
Loran-C TDs
GPS receiver status
summary
Page 5-2
The 961 uses a high-performance GPS receiver as its primary
source of position data. Calculated directly from the received
satellite data are your present position in lat/lon coordinates,
time of day and date, speed-over-ground (SOG) and
course-over-ground (COG), and an estimate of the 961's accu-
racy.
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 pressing the first
INFO key, a second INFO key is displayed, letting you display
additional data on the second INFO BAR.
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; GPS speed is updated every
second. You can set the 961 to display its SOG and COG read-
ings more smoothly by setting the GPS speed averaging value
up to 10 seconds. Increasing this averaging time, however,
may reduce overall reaction time. For details about GPS speed
averaging value, see "Changing GPS speed averaging value"
starting on page 14-5.
The 961 also calculates Loran-C TDs from the GPS coordi-
nates, and displays them on the CHART-screen INFO BARs. For
details, see "Viewing loran TDs" starting on page 5-9.
To display information about the GPS satellites, press the
STAR key to display the SERVICE MENU screen, then press
the GPS STATUS key. The 961 displays the GPS SATELLITE
STATUS screen, showing the status of the GPS receiver. This
screen also displays the status of the DPGS receiver, if installed
(961XD).
961 Operations and Reference Manual Rev. D