With ever greater use of GNSS services worldwide for land surveying purposes, it is of paramount importance, that adequate correction services are available to the users. With ESA’s brand new Galileo satellite constellation system already working, Trimble made a step forward in using this technology in everyday life. They announced recently, that its Trimble® VRS Now networks, which is powered by its own software (called by Trimble Pivot Platform) can now process Galileo observation data in its network-modeled Virtual Reference Station (VRS) solution. As a true five-constellation technology using GPS, GLONASS, BeiDou, Quasi-Zenith Satellite System (QZSS) and now Galileo observations, Trimble VRS is now capable of delivering ever better real-time positioning data to it’s customers throughout much of Europe.
VRS – how does it work ?
To reach centimeter- or sub-centimeter level accuracy of positioning typically requires use of precise dual-frequency carrier phase observations. Furthermore, these observations are usually processed using a differential GNSS (DGNSS) algorithm, such as real time kinematic (RTK) or post-processing (PP). The virtual reference station (VRS) concept can help reaching desired accuracy by using a network of reference stations (i.e. SIGNAL). As a quick review, a typical DGNSS setup consists of a single reference station from which the raw data (or corrections) are sent to the rover receiver (i.e., the user). The user then forms the carrier phase differences (or corrects their raw data) and performs the data processing using the differential corrections.
In contrast, GNSS network architectures often make use of multiple reference stations. This approach allows a more precise modeling of distance-dependent systematic errors principally caused by ionospheric and tropospheric refractions, and satellite orbit errors. More specifically, a GNSS network decreases the dependence of the error budget on the distance of nearest antenna.
Technology and benefits
With accessibility to the Galileo constellation, users now have visibility to more satellites, which can be advantageous in environments where line of sight may be limited. Surveyors, mapping and GIS professionals and other industries now have a more versatile and robust VRS Now correction solution.
Adding Galileo to Trimble VRS Now technology provides significant benefits to it’s users:
- Increased number of in-view satellites, improved accuracy and reliability of corrections
- Improved positioning integrity using observations from additional satellites to better eliminate errors
- Enabling higher cut-off angles, delivering better performance in urban ares and other not so optimal environments (i.e. dense vegetation)
- Minimized multipath and interference through the addition of available satellite signals
As mentioned before, VRS Now Europe is powered by the Trimble Pivot Platform, which is the only VRS networking software on the market today capable of using Galileo observation data. This means it is capable of improving positioning performance and integrity for VRS Now users, which the competition cannot yet achieve. No other VRS service provider using five-constellation support (to date) has a larger footprint in Europe.
Galileo support is available with any Trimble VRS Now subscription in Belgium, The Czech Republic, Estonia, Germany, Great Britain, Ireland, Luxembourg, The Netherlands and Sweden using a compatible GNSS receiver or display. It is also available in some parts of the USA and Australia. Trimble VRS Now can deliver an initialization time of less than 1 minute, enabling work to begin quickly. Professional management and monitoring by a global operations team provides peak performance and high reliability. Hopefully, this service will also be soon available in other European countries, but first, some of them have to update their respective reference station system to support new constelations and technologies.
sources: http://www.insidegnss.com/node/2687, http://www.trimble.com/positioning-services/vrs-now.aspx?tab=How_it_Works, http://www.trimble.com/news/release.aspx?id=061517a