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 Using the Web User Interface) or in the Manager application (see Using Certus Manager). It is possible to use multiple heading sources and this can provide performance benefits.

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 Navigation Specifications). A minimum 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.

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 vehicles that don't move sideways. Velocity heading cannot work for helicopters and other vehicles where the vehicle is pointed somewhere other than the direction of travel. Velocity heading requires a horizontal speed of over 1.15 m/s with a GNSS fix. Velocity heading is disabled by default.

Magnetic Heading

This is the default heading source and works well in the majority of cases. When using magnetic heading, magnetic calibration is required every time the static magnetic field around the Certus changes. This can occur, for example, when moving the mounting location of the unit, or making significant structural changes to the vehicle that alter the distribution of ferrous materials. The downside of magnetic heading is that prolonged exposure to dynamic magnetic interference can cause significant heading errors. See Magnetics and Magnetic Calibration for further information. Magnetic heading is enabled by default.

External Heading

This can be used if there is some other way to derive heading that is external to Certus. The heading must be supplied to Certus using the External Heading Packet or an NMEA message, see NMEA Input.

External Magnetometers Packet

Heading can derived using the magnetometers of an additional external Advanced Navigation product to input external magnetometer values. See External Magnetometers Packet for details.