Specifications

8 | Operation
Manual for more details. Turning this feature ON in the
MX420 CDU will initiate the MX521 to listen for and track
any SBAS satellites that are in view.
Receiver Autonomous Integrity
Monitoring (RAIM)
RAIM is a special software algorithm in the MX521A
program which gives the operator timely warnings when
the GPS system accuracy is questionable. This feature
requires at least five or more GPS satellites to operate
properly. If the position solution error exceeds a preset
limit a “RAIM Unsafe (R-)” or ”RAIM Caution (R?) alarm
will be indicated in the MX CDU. This means that the
accuracy of the position can not be guaranteed to be
very accurate at that point in time. The operator is
advised to use the GPS cautiously for navigation until
the RAIM indicator switches to (R+) denoting safe RAIM
condition.
Position errors may be caused by unhealthy satellites,
incorrect pseudoranges, poor satellite geometry,
excessive atmospheric interference and problems at
particular reference stations.