Table 3-17. GPS Status Codes
Navigation with altitude aiding
Navigation with data collection
In the initialization stage, the GPS receiver is in
the process of initializing and collecting information
such as the date, time, and last position. 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 from
them is being obtained.
The transition stage indicates an adequate
number of satellites for navigation has been acquired
and is being tracked, but no position data can yet be
Normal navigation is indicated by a NAV, NAV A,
or a NAV D GPS state. NAV A indicates that the
altitude input is being used in the position solution.
NAV D indicates that besides calculating position, the
receiver is collecting and storing in its memory
ephemera and almanac data information.
The specific GPS satellites or Space Vehicles
(SV), being received are displayed in the left column.
Each satellite has its own identification number. An
asterisk (*) to the left of the satellite indicates this
particular satellite is not presently being used in the
The satellite's health, transmitted by satellite, is
indicated to the right of the satellite number. Health
designators are defined in Table 3-18.
The Signal to Noise Ratio (SNR) for each
satellite being received is displayed in the middle
column and indicates the signal strength for each
satellite. The higher the SNR value, the stronger the
signal. Values usable for navigation will be in the mid
30's to 50's. Typical values are in the middle of this
Table 3-18. Satellite Health
The elevation (ELE) above the horizon for each
satellite is provided in the right column and will range
from 5 ° to 90°. Refer to Figure 3-111.
(2) STA 2 Page. The STA 2 page displays
the systems estimate of the position error expressed in
nautical miles. Refer to Figure 3-112. The KLN 90B's
position error depends on such factors as the number
of satellites being received, the strength of the GPS
signals, and the geometry of the satellites presently
being used for navigation.
SV SNR ELE
02 40 11o
11 42 47o
16 36 06o
*18B 33 65o
Figure 3-111. STA 1 Page
Figure 3-112. STA 2 Page