Simrad HS52, Instruction Manual

Page: 52 / 80

Simrad HS52 GPS compass and DGPS navigator
44
20222360 / E
The integrity indication for different position accuracy levels are
expressed in three states that satisfies the requirements in IEC
61108-1 second edition 2003-07. The states are Safe, Unsafe
and Caution. On the display, the visual indicators are shortened
into SAFE, CAUTN and USAFE. The position accuracy level is
selectable from the display and is normally between 10m and
100m, see page 34 for setup of the accuracy level.
The system integrity value is often referred to as the horizontal
external reliability. It gives an indication of how large a
horizontal position error might be at the condition of an arbitrary
undetected satellite failure.
Safe
indicates that the system accuracy is better than the
selected accuracy level and that a single satellite failure can not
make the actual horizontal position error exceed the selected
accuracy level (95% confidence level).
Caution
indicates that the system accuracy is better than the
selected position accuracy level, but a single satellite failure
might not be detected, and at failure the actual horizontal
position error might exceed the selected accuracy level (95%
confidence level). At four satellites (three when height aiding is
chosen), there is no way to detect a satellite failure and the
system will always be in the state caution. The expected
accuracy and HDOP might still be reasonable good.
Unsafe
indicates that the system accuracy has exceeded the
selected accuracy level (95% confidence level).