Time; Heading Sources; Dual Antenna Heading; Velocity Heading - Advanced Navigation Certus OEM Reference Manual

Certus Reference Manual • Using Certus
Whenever Certus is without power it continues to accurately keep time so that it is immediately valid for a hot-
start.
The hot-start functionality is of particular benefit to vehicle tracking and robotics applications. The primary
benefits are immunity and fast recovery from power failure as well as fast start up time.

7.3 Time

Certus is designed to provide a highly accurate time reference via an internal oscillator.
The oscillator is a temperature compensated disciplined oscillator.
For a device with a GNSS receiver, when GNSS fix is available the internal oscillator uses GNSS time to
precisely correct itself within an accuracy of 20 nanoseconds.
When the GNSS fix is lost, the time will slowly lose accuracy.
When Certus hot-starts, time accuracy is typically achieved within 1-2 seconds after a GNSS fix is achieved.
The time can be accessed via the following means:
A dedicated 9.3 1PPS
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A 1PPS output over GPIO or the Auxiliary port, see
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A built-in Precision Time Protocol (PTP) version 2 server for synchronisation with network-connected
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devices which require high accuracy time. The PTP server broadcasts PTP messages (Sync, Follow Up,
Announce) to multicast IP address 224.0.1.129. The PTP broadcasts are sent whenever an Ethernet
connection is established and cannot be disabled.
A built-in Network Time Protocol (NTP) server.
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7.4 Heading Sources

There are several different heading sources available for Certus. The heading sources can be configured using
the Filter Options page in the web UI (see
(see 8.2 Using Certus
performance benefits.

7.4.1 Dual Antenna Heading

For devices that support dual GNSS antenna input, this is the heading source that provides the most accurate
heading while GNSS is available. Dual antenna heading only works when a good GNSS fix is available to both
antennas. It requires a clear view of the sky with minimal nearby sources of interference or multipath. The
greater the antenna separation, the higher the accuracy (see
antenna separation of 0.5 metres is required.
Certus will operate with a single primary antenna connected, but this will prevent dual-antenna heading being
used, although velocity heading will still be possible.

7.4.2 Velocity Heading

For devices that support either single or dual GNSS input, velocity heading works by deriving heading from the
direction of velocity and acceleration. Velocity heading works well with cars, fixed wing aircraft and other
v2.4
Signal. This is the preferred means to obtaining the most accurate timing output.
8.1 Using the Web User
Manager). It is possible to use multiple heading sources and this can provide
9.6.1.2 1PPS Output
Interface) or in the Manager application
5.1 Navigation
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of the Dynamic Pin Functions.
Specifications). A minimum
2024-12-17