Time; Heading Source; Dual Antenna Heading; Velocity Heading - Advanced Navigation Spatial Dual Reference Manual

10.3

Time

Spatial Dual was designed to provide a highly accurate time reference. When a GNSS
fix is available Spatial Dual's time is accurate to within 50 nanoseconds. When a GNSS
fix is lost, Spatial Dual's time accuracy typically remains within 10 microseconds over
extended time periods. When Spatial Dual hot starts the time accuracy is typically
within 1 second immediately on startup and corrected to within 50 nanoseconds as
soon as a GNSS fix is achieved. To synchronise with Spatial Dual's high accuracy time,
both the packet protocol and a 1PPS line must be used.
10.4

Heading Source

There are three different heading sources available for Spatial Dual. The heading
sources can be configured using the filter options dialogue in Spatial Dual Manager. It
is possible to use multiple heading sources and this can often provide performance
benefits.
10.4.1

Dual Antenna Heading

This is the default heading source and provides very accurate heading while GNSS is
available. Dual antenna heading only works when there is a good GNSS fix available. It
requires a clear view of the sky with minimal nearby sources of interference or
multipath.
10.4.2

Velocity Heading

Velocity heading works by deriving heading from the direction of velocity and
acceleration. Velocity heading works well with cars, boats, fixed wing aircraft and other
vehicles that don't move sideways. Velocity heading does not work with helicopters
and other 3D vehicles. Velocity heading can only be measured when the vehicle
travels at a horizontal speed of over 1.15 metres/second with a GNSS fix. It is
recommended not to use velocity heading with Spatial Dual unless there is problems
achieving a dual antenna heading fix.
10.4.3

External Heading

This can be used if there is some other way to derive heading that is external to
Spatial Dual. Examples include north seeking gyroscopes, reference markers and SLAM
systems. The heading must be fed into Spatial Dual using the External Heading Packet
or through NMEA into a GPIO pin.
10.5

Sensors Range

Spatial Dual supports dynamic ranging on it's sensors. Each of the three sensors have
three different range levels. At lower ranges the sensor performance is better, but at
higher ranges Spatial Dual can be used in more extreme dynamics. The goal is to
choose the lowest range that your application won't exceed.
Sensor over range events can be detected in the filter status, see section 13.9.1.2. In
Spatial Dual manager the status indicator will go orange indicating that a sensor has
gone over range. When a sensor goes over range this causes the filter to become
Spatial Dual Reference Manual
Page 45 of 137
Version 2.3
12/04/2016