Version 2.0
189
Engineering Mode
Operator’s Manual
GPS4 - GPS Position Uncertainty
This screen presents a bar graph representing the HDOP for the past
23 hours. If you are trying to do precision work or navigation in the
same general area (within 100 miles) as the day before, you can look at
this screen to see when the best HDOP periods are. The GPS constel-
lation shifts back 4 minutes per day. That means you can expect the
GPS coverage to be virtually the same today as it was yesterday.
The small 1 hour gap in the bar graph represents the 24th hour. The
gap is provided to ease the readability of the bar graph for the present
time. The dashed line extending horizontally from the 4 represents the
current
HDOP Limit Alarm
, which is set in
CFG
Position
. The current
HDOP and VDOP values are given in the upper window.
MX Ant Reset & CSI Reset Tools
Special tools are available in the MX420 CDU that can be used to reset
the GPS and Beacon engines in the MX421. Use them only in extreme
cases when the GPS or beacon receiver fails or takes too long to lock-
on. The “MX Ant Reset” softkey will clear the satellite almanac memory
of the GPS engine and reset all settings of the antenna to factory
default conditions. The “CSI Reset” softkey resets the differential bea-
con board.
MX Ant Reset Procedure:
This procedure will work only under Engineering level mode.
1. Press the
AUX
key several times to bring up the AUX7 screen.
2. Press the left-most softkey 3 times (to bring-up Eng’g level 3).
3. Press the
E
key.
4. Press the
“MX Ant Reset”
softkey to reset the GPS engine (or
the
“CSI Reset”
softkey to reset the beacon engine).
5. Press the
E
key to exit.
6. Press the
GPS
key to display the GPS or DGPS Status screen.
Summary of Contents for MX420
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