Oxford Technical Solutions Ltd Page 16 of 110
Quad constellation
Tracking satellites from GPS, GLONASS, Galileo and BeiDou constellations allows the RT to utilise all the
available position satellites.
In open sky conditions, this benefit is smaller as GPS signals alone 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, quad constellation 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.
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. The RT3000 T v4 includes the necessary hardware to receive these
corrections. It is necessary to pay a licence fee to activate these corrections. Capable RT systems will use the
TERRASTAR-C service which can provide better than 3 cm position accuracy. TerraStar is available on all
continents. Marine versions also exist.
For more information, see TerraStar’s website: http://www.terrastar.net.
To Next Page
Loading...
General