Using Dgps - NorthStar 941X Reference Manual

datum
status summary

Using DGPS

Page 26
The 941X's speed and course readings are the result of instan-
taneous measurements derived from satellite signals. GPS
speed is updated every second. However, you may average
these readings by changing the "GPS speed averaging" value
(see page 87).
In the center of the screen, the name of the datum currently in use is dis-
played. The datum describes the reference of the chart you are currently
using (the reference datum used is indicated on each chart). Applying the
datum corrects for any position differences between your chart and the
GPS coordinate system. See "Geodetic Datum," on page 94, for more in-
formation on selecting the datum for your area.
When using differential GPS (DGPS) as your navigation
source, your position, as displayed by the 941X, may actually
exceed the accuracy of some charts.
At the top center of the position screen is a brief status summary of the
GPS receiver. The following table shows the various status messages the
941X may display, along with their meanings.
Message Meaning
ACQUIRE
trying to acquire satellites
SKY SEARCH
searching for satellites with no previous information
TRACKING
satellites have been acquired; almost ready to navigate
2D NAV
navigating with 3 satellites in 2-D mode
3D NAV
navigating with 4 or more satellites in 3-D mode
POOR FIX
tracking satellites with poor geometry/accuracy
COMM FAIL
communication link to GPS sensor has failed—unit
needs repair
In the upper right corner of the GPS POSITION screen is an indicator
that shows whether Differential GPS (DGPS) corrections are in use. If
your installation includes an optional Northstar internal differential GPS
receiver, or other external source of differential corrections, navigational
accuracy will be significantly improved when this indicator is present.
3 — Basic Navigation 3 — Basic Navigation 3 — Basic Navigation 3 — Basic Navigation
NOTE
NOTE
Rev. D