xFill

Most RTK systems currently rely on radio or cellular connections to receive corrections from a reference station. Trimble xFill technology aids standard RTK systems in the event of connection outages with their primary source of corrections: a physical reference station or a Virtual Reference Station (VRS) stream.

A typical case of radio drop-out is radio signal shadowing caused by a building. The signal outage takes place at the rover locations where the building is between the user and the reference station radio transmitter, effectively blocking the signal and causing a suspension of RTK positioning. The same scenario can occur when a VRS user moves to an area where a large building or hill blocks communication with the active cellular tower.

Trimble RTX technology currently powers stand-alone positioning services for several non-survey applications. Trimble xFill, which is a standard feature with the Trimble geospatial ProPoint? GNSS Receivers, is not a stand-alone positioning service but instead uses the RTX infrastructure, which also powers CenterPoint RTX, to augment standard RTK and VRS surveying methods. In the event of a correction outage, such as the one illustrated in Figure 3, the Trimble RTX corrections provide the mechanism to maintain high precision RTK positioning based on just the rover GNSS observables. This “fills the gap” caused by the primary correction stream outage (hence the feature name “xFill”).

As a result of the continuously broadcasting stream of corrections from Trimble RTX satellites, it is also possible to continue operating for the entirety of a radio outage or a loss of cellular coverage by using Trimble xFill Enhanced. xFill Enhanced operates using the same functionality as Trimble xFill correction service, but continues to provide a precise solution after xFill times out.

1. Precisions are dependent on GNSS satellite availability. xFill positioning ends after 5 minutes of radio downtime.
2. RTK refers to the last reported precision before the correction source was lost and xFill started.
3. Precisions are dependent on GNSS satellite availability. xFill Enhanced continues providing centimeter-level accuracy until your RTK correction is restored.