RTK, Trimble RTX, Trimble xFill, and Trimble ProPoint

RTK

Real-Time Kinematic (RTK) positioning is positioning that is based on at least two GPS receivers—a base receiver and one or more rover receivers. The base receiver takes measurements from satellites in view and then broadcasts them, together with its location, to the rover receiver(s). The rover receiver also collects measurements to the satellites in view and processes them with the base station data. The rover then estimates its location relative to the base.

The key to achieving centimeter-level positioning accuracy with RTK is the use of the satellite carrier phase signals. Carrier phase measurements are like precise tape measures from the base and rover antennas to the satellites. In the receiver, carrier phase measurements are made with millimeter-precision. Although carrier phase measurements are highly precise, they contain an unknown bias, termed the integer cycle ambiguity or carrier phase ambiguity. The rover has to resolve, or initialize, the carrier phase ambiguities at power-up and each time the satellite signals are interrupted.

Trimble RTX

The Trimble RTX® technology provides real-time, centimeter-level GNSS corrections with high-level accuracy delivered worldwide via satellite or cellular/IP. RTX services available are:

  • CenterPoint® RTX

    MPS566 receivers activated after 1 April 2024 includes an activated and ready-to-use one year Centerpoint RTX subscription. At the end of the 12-month period, you can renew the CenterPoint RTX subscription at the listed price. For more information and instructions on how to configure Trimble RTX with your Trimble software, go to positioningservices.trimble.com/en/rtx-on-point.

  • FieldPoint RTX

  • RangePoint® RTX

  • ViewPoint RTX®

The accuracy differs for each service. The MPS566 receiver supports the CenterPoint RTX service.

For more information, see positioningservices.trimble.com/en/rtx.

Trimble xFill

The Trimble xFill® technology provides seamless, centimeter-level back-up corrections via satellite if RTK or VRS signal sources are interrupted due to signal disruptions or loss of radio connectivity.

xFill is included in the MPS566 receiver. xFill Premium (xFill-RTX) is subscription-based enabled by having a valid CenterPoint RTX (or CenterPoint RTX Fast) subscription on the receiver.

The xFill feature takes less than five minutes to be initialized and ready. To use xFill, RTK needs to be running for up to five minutes while the receiver is also getting the RTX correction stream.

After losing the RTK correction stream, xFill will start providing positions that slowly drift, and the receiver will cut it off at five minutes and drop to Autonomous in the absence of any alternative correction source.

If using xFill Premium, the receiver simultaneously processes RTK and RTX positions. When RTK is lost, it will transition to xFill, and then xFill Premium. The transition to xFill Premium occurs when xFill accuracy becomes worse than RTX accuracy, or at ten minutes since RTK correction loss; whichever happens first. xFill Premium (xFill-RTX) positioning will continue until the RTK correction source is regained.

The receiver's position type will show 'xFill", or "xFill-RTX" (i.e. xFill Premium).

For more information, see About the Trimble xFill service.

Trimble ProPoint engine

The MPS566 receiver includes the Trimble ProPoint® engine. It is the fifth generation high-precision positioning engine that fuses GNSS signals, correction services, and measurement data from various sensors, including INS if enabled, to provide positions and orientation. It:

  • provides a more accurate solution in challenging GNSS environments such as urban canyons, tree canopy, and under bridges.

  • has improved GNSS constellation-agnostic operation. All constellations are considered equally valuable.

  • is better able to cope with spoofing and jamming by flexible use of all available signals.

  • has better dynamic modeling to suit the application. The marine dynamic model allows for side-to-side motion and lateral drifting.

  • has more robust precision estimation.

  • has Integrated RTK xFill for continuous RTK operation.

  • has positions with less than 20 ms latency at update rates up to 50 Hz.

For more information, see oemgnss.trimble.com/technologies/trimble-propoint-gnss/.