BendixKing KLN 94 - Pilots Guide - Manual (Page 156)

sufficient “geometry” exists to determine an accurate position. The satellite
constellation geometry is continually changing as each satellite, “rises”,
travels across the sky, and eventually “sets” relative to your position. The
GPS satellites are not in geosynchronous orbits positioned over the same
spot on earth at all times like some television communication satellites
with which you may be familiar. Rather, the GPS satellites are in orbits
that allow them to circle the earth about two times each day.
A representative AUX 1 page is
shown in figure 5-53. The AUX 1
page displays the GPS receiver state
and the system’s estimate of the
position error expressed in nautical
miles or kilometers.
The GPS state is indicated on line 2. The possibilities are:
INIT initialization
ACQ acquisition
TRAN transition
NAV navigation
NAV A navigation with altitude aiding
NAV D navigation with data collection
DEGRD navigation with position degradation
FAILR receiver failure
In the initialization state the GPS receiver is in the process of initializing
itself, collecting information such as the date, time, and last present posi-
tion. Next, the receiver collects data from its own memory to determine
which satellites should be visible. After completing the initialization
process the receiver begins the acquisition process. During this time, the
visible satellites are being acquired and data is obtained from them.
The transition state indicates an adequate number of satellites for naviga-
tion has been acquired and is being tracked but no position data can yet
be produced.
Normal navigation is indicated by a NAV, NAV A, or NAV D GPS state.
NAV A indicates that the altitude input is being used in the position solu-
tion. NAV D indicates that besides calculation position, the receiver is
collecting and storing in its memory additional data from the satellites
(called ephemeris and almanac data).
Line 3 of the AUX 1 page displays the present GPS-derived altitude, that
is, the altitude that is being indicated by the GPS position solution.
Chapter 5 Intermediate Operation
5-22
Figure 5-53