BendixKing KLX 135A - Pilots Guide - Manual (Page 86)

3.13. THE OTHER (OTH) PAGES
3.13.1. DETERMINING THE STATUS OF THE GPS SIGNALS
The Other (OTH) 1 and OTH 2 pages may be viewed at any time to
determine the status of the GPS receiver and the GPS satellites
being received. This includes which satellites are being tracked, the
satellites’ health, the signal-to-noise ratio for each of these satellites,
the elevation of each satellite above the horizon, and the estimated
position error.
The GPS receiver in the KLX 135A is capable of using signals from
up to eight satellites to determine its position. A valid position may be
determined using as few as four satellites alone or three satellites
with a valid altitude input. However, four satellites alone or three
satellites with an altitude input do not necessarily ensure that
navigation can take place. The satellites must be positioned relative
to your location such that sufficient “geometry” exists to determine an
accurate position. the satellite constellation geometry is continually
changing as each satellite, “rises”, travels across the sky, and
eventualy “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 OTH 1 page is
shown in figure 3-168. The OTH 1
page displays the GPS receiver state
and the system’s estimate of the posi-
tion error expressed in nautical miles.
The GPS state is indicated on line 1. The possibilities are:
INIT initialization
SRCH search the sky
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
KLX 135A Pilot’s Guide Basic GPS Operation
3-57 Effective Date 5/95 006-08789-0000 Rev 0
Basic GPS Operation
Chapter 3
APT VOR NDB SUP ACT NAV FPL CAL SET OTH
118.00 State NAV D
136.97
>Leg Estimated Posn
OTH 1 Error 0.02nm
Figure 3-168