12
Oxford Technical Solutions
The heading software in the RT enables significantly better performance and coverage
compared to GNSS-only solutions.
GLONASS
GLONASS capability adds the ability to utilise the Russian satellite constellation
GLONASS as well as the American constellation GPS. This means an extra 24 satellites
are available for the RT to lock on to and obtain position and velocity updates from.
In open sky conditions, the addition of GLONASS capability is of little benefit as the
GPS signals are unlikely to be interrupted and full accuracy can be achieved almost 100%
of the time. However, in open-road testing situations there are likely to be bridges, trees,
and tall buildings that can block the view of satellites or cause multipath effect errors. In
these situations, GPS and GLONASS receivers are able to maintain 1 cm accurate RTK
positioning mode at times when GPS-only receivers are not. They are also able to re-
establish RTK lock and resolve its ambiguities after an obstruction faster.
BeiDou
BeiDou capability adds the ability to utilise the Chinese satellite constellation BeiDou as
well as the American constellation GPS and Russian constellation GLONASS. This
means an extra 34 satellites are available for the RT to lock on to and obtain position and
velocity updates from.
250 Hz
1.
All products (including the RT1003) have the option of coming with a 250 Hz version
of the inertial measurement unit (IMU).
Satellite differential corrections
To improve the positioning accuracy of standard GNSS, two satellite-based differential
correction services are available. These are SBAS and TerraStar.
Services such as WAAS and EGNOS, are wide-area differential corrections provided for
free. They can provide an accuracy of better than 1 m CEP. WAAS is available in North
America; EGNOS is available in Europe; MSAS is available in Japan; GAGAN is
available in India; SDCM is available in Russia. Other parts of the world are not covered
and cannot use this service.
TerraStar is a subscription service. RT systems that have TerraStar capability include the
necessary hardware to receive corrections. It is necessary to pay a licence fee to activate these
corrections. Capable RT systems will use the TERRASTAR-D service which can provide better
than 10 cm position accuracy. TerraStar is available on all continents. Marine versions also exist.
For more information, see TerraStar’s website: