EndRun Meridian II, Руководство пользователя

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M e r i d i a n I I U s e r M a n u a l 140
C H A P T E R T W E L V E
141 M e r i d i a n I I U s e r M a n u a l
F R O N T - P A N E L K E Y P A D A N D D I S P L A Y
TFOM: This is a value between 3 and 9 and indicates clock accuracy.
A detailed explanation of TFOM is in
Appendix A - TFOM
.
Receiver State: This shows the current state of the GPS Receiver as follows:
ACQ: Acquring. Searching for a signal.
LKG: Locking to the GPS signal.
LKD: Locked. Fully synchronized to signal.
The GPS Receiver is synchronized to the signal and it is
providing valid measurement data to the GPS Subsystem pro
cessor.
# of SVs: This shows the number of currently tracks Satellite Vehicles from 0 to 12.
AGC This is the automatic gain control DAC byte, 0 to 255, with larger numbers
implying higher RF gain. With good signal conditions this value is typically 125
to 200.
Avg C/No: The carrier-to-noise ratio is an indicator of the GPS signal quality. This
number typically ranges from 39 to 50 dB when the instrument is locked.
SV ID#: This field lists the satellite vehicles that are currently being tracked.
Receiver: Satellite Vehicle Information (SV_Info)
This displays shows the channel number, SV number, azimuth, elevation and the carrier-to-noise ratio
(C/No) for all 12 channels of the 12-channel GPS Receiver. SV number 0 is an invalid number and
indicates that no satellite is being tracked on that channel. Valid SV numbers range from 1 to 32.
Azimuth and elevation are in degrees and C/No is in dB.
Receiver: Reference Position (Ref_Pos)
This display shows the current GPS reference position and allows you to enter a position, if desired.
The GPS reference position is the position of the GPS antenna. Accurate position is necessary to
generate precise time and frequency outputs.
The position is shown as latitude, longitude and elevation. Latitude and longitude are shown as
hemisphere (North, South, East, West), degrees, minutes and seconds. Elevation is shown in meters
above the WGS-84 ellipsoid. By scrolling down, the RMS PDOP and Average Count are shown for
the averaged position. These will be zero if the source of the position is not “average”. A complete
average consists of 28800 fixes.
The source field (SRC) indicates the source of the position information. Possible values are “un-
known”, “average” and “user”. When first installed, the position source will be “unknown”. It
changes to “average” after the receiver has computed the first 3-dimensional position fix. The posi-
tion continues to be averaged for about 24 hours. Computation requires that a minimum of 4 or
more satellites be in view.
With a rooftop antenna installation that has an unobscured view of the sky, the instrument will de-
termine position automatically. Once determined, the position information is saved in non-volatile