Sperry Marine Visionmaster FT ECDIS User Manual page 502

System
Data State
Dead Reckoned
Implausible
Inaccurate
Invalid
Manual
Nearly Valid
Nearly
Unavailable
Over the FOM
Limit
13-18
A long period of time has passed since an actual
measurement of the data was received. Since that time,
the data has been adjusted to make it correct for the
current time. However, this adjustment (performed using a
dead reckoning or estimation algorithm) may not be very
accurate. When data is dead-reckoned, it is considered
usable, but degraded.
The data is not within reasonable limits or it is changing at
an unreasonable rate. When this applies, the data is
considered unusable.
There is a possibility that the data is not accurate, based
on some of the information being supplied by the sensor.
For example, if position data is supplied in a datum other
than WGS84, and the sensor does not supply the offset
needed to adjust it to WGS84, the data will be considered
inaccurate. When this applies, the data is considered
usable, but degraded.
The sensor providing the data is indicating that the data is
not valid. When this applies, the data is considered
unusable.
The data was manually entered. When this applies, the
data is considered usable, but degraded.
The source of this data is indicating "Invalid" for some of
the samples it is providing. If a higher percentage of
samples are received with the "invalid" indication, then the
data may be indicated as absolutely invalid, in which case
it will be considered unusable. When "Nearly Invalid", data
is considered usable, but degraded.
The system has received fewer than the expected number
of samples over a recent timespan. If even fewer samples
are received, the data may become "Unavailable", in
which case it will be considered unusable. When "Nearly
Unavailable", data is considered usable, but degraded.
Position sensors can be configured for a maximum figure
of merit. If a position sensor indicates that its position
data has a figure of merit greater than the configured
maximum figure of merit, then the system will indicate that
the data is "over the FOM limit", which results in the data
being considered degraded.
Description
ECDIS User Guide
65900012