GNSS Correction Sources

Your GNSS operations are only as good as your correction source. It’s important, so we let you choose the right one for you. Larger sites may need a local GNSS base station for the highest precision. Smaller sites may opt for a virtual correction source.

Features and Benefits

GNSS alone does not give the high level of accuracy needed on a construction site. The accuracy and integrity of GNSS can be greatly enhanced by using a GNSS correction service. GNSS correction sources take many forms, but all provide information that improves GPS/GNSS performance and precision.

  • Single Base RTK – RTK Base, Internet Base Station Service (IBSS)
  • Mobile Satellite Services or MSS – RTX, OmniSTAR
  • Network RTK – VRS Now or VRS
  • Differential GNSS (DGNSS) – DGNSS Base, MSK Beacon, IBSS
  • Satellite Based Augmentation Systems (SBAS)

For larger construction sites and those that include both site positioning and machine control operations, we recommend you deploy the Trimble SPS855 GNSS Modular Receiver as a permanent or semi-permanent base station.

For additional information on which external antenna to choose for your base station please call our team on 9392 7700.

Trimble VRS is a Network  Real-Time Kinematic (RTK) subscription service delivered via the Internet over a cellular network. Like the MSS services, VRS is ideal for construction sites where it is not practical to set up a base station, such as sites where there is no machine control or for initial reconnaissance tasks where a base station is not yet established.  VRS does require an Internet connection at the rover. Utilizing Trimble VRS technology, centimeter level accuracy is available on demand, anywhere within the reference station network. It’s highly cost effective and efficient, super convenient, simple to use, and, best all, it’s always on.

Trimble xFill runs seamlessly in the background, automatically bridging the gap if a user’s RTK or VRS correction source is interrupted due to cellular signal disruption or loss of UHF radio connectivity. Trimble xFill is a satellite-delivered service that will maintain RTK precision for five minutes after the loss of an RTK correction stream.

Trimble Internet Base Station Service (IBSS) broadcasts Real-Time Kinematic (RTK) data or Differential (DGNSS) corrections from your base station over the Internet via Wi-Fi or a cellular network. This makes it easier and more economical to use high precision GNSS for site positioning or machine control on the construction site over ranges which exceed the limitation of the UHF radio link. IBSS can also be used to augment UHF in areas of poor UHF coverage.

Satellite-based GNSS correction services include Trimble RTX and OmniSTAR. MSS delivers real-time and highly reliable positioning services for land-based construction sites worldwide, 24 hours a day, 365 days a year.

MSS is delivered via geo-stationary L-band satellites, the signal is received at the GNSS rover by the Trimble GNSS antenna or GNSS Smart Antenna, so there is no requirement for a UHF radio or cellular network connection.

MSK Beacon refers to a DGNSS or DGPS reference stations maintained mostly by the International Association of Marine Aids to Navigation and Lighthouse Authorities (formerly IALA) which transmit a free differential correction service on the 300 kHz band. Trimble marine GPS/GNSS receivers with the appropriate MSK capable antenna can use these corrections at no cost for sub-meter positioning.

The Satellite-Based Augmentation System (SBAS) is based on GNSS measurements from accurately-located reference stations deployed across an entire continent. The differential corrections and integrity messages are broadcast over a continent using geostationary satellites as an augmentation or overlay of the original GNSS message. Systems in place are WAAS (USA), EGNOS (Europe), GAGAN (India) and MSAS (Japan) which deliver corrections at no cost for sub-meter positioning.