GNSS Correction Sources

Flexibility for Your Business


Your GNSS operations are only as good as your correction source, it’s important to choose the right one for your business. GNSS correction sources are available on-site in a variety of ways, depending on what you need for your jobsite. Choose to run a local base station on site, obtain corrections from a local VRS Now network service or even obtain corrections from the satellite delivered CenterPoint RTX correction service.

GNSS Correction Sources

If you are running a large operation with many machines, you will need a local GNSS base station (or a few) and if you are site surveying or doing reconnaissance you may opt for a high accuracy satellite delivered service such as CenterPoint RTX.

Trimble GNSS Real-Time Kinematic (RTK) Base Station

For larger construction sites and those that include both site positioning and machine control operations, we recommend you deploy the Trimble R750 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 visit the Trimble GNSS Antennas for Construction web page, or contact your SITECH Technology Provider or Trimble Marine Dealer.

Network Real-Time Kinematic (RTK)

Trimble VRS Now is a Network RTK subscription service delivered via the internet over a cellular network. Like mobile satellite services (MSS) services, VRS Now 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 Now requires an internet connection at the rover. Utilizing Trimble VRS technology, centimetre level accuracy is available on demand, anywhere within the reference station network. It is highly cost effective and efficient, convenient, simple to use, and best of all it’s always on.

CenterPoint RTX

CenterPoint RTX is the premier mobile satellite services (MSS) technology delivering VRS-level performance 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 need for a UHF radio or cellular network connection.

Trimble xFill

Trimble xFill runs seamlessly in the background, automatically bridging the gap if a user’s Real-Time Kinematic (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.

Internet Base Station Service (IBSS)

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 Augmentation System (SBAS)

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 delivering corrections at no cost for sub-meter positioning are:

  • WAAS (USA)
  • EGNOS (Europe)
  • GAGAN (India)
  • MSAS (Japan)

Correction Source Comparison

Use the technical specifications below to decide on the source that makes sense for your workflow and performance and precision requirements.


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