Position

Use this page to set receiver position-related settings.

Select Receiver Configuration / Position.

 

PDOP Mask – Use the PDOP mask to enter the value for PDOP above which the calculation of new RTK positions is suspended until the PDOP falls below the mask value again. A DGPS position is output when the PDOP for the RTK position exceeds the PDOP Mask.

RTK Mode – Set the RTK Mode to Synchronous or Low Latency.

• Synchronous – The rover receiver must wait until the base station measurements are received before computing a baseline vector. Therefore, the latency of the synchronous position depends on the data link delay. A synchronous RTK solution yields the highest precision possible but is subject to latency. This mode is suitable for static and low-dynamic positioning.

• Low Latency – Provides a slightly lower precision solution than Synchronous mode but with a constant low latency, typically less than 20 msec. This mode is ideal for high-dynamic positioning where latency is an issue.

Autonomous/Differential Engine – By default, the Kalman filter is on and results in higher quality position solution for autonomous or DGPS solutions when compared with a Least Squares solution. The Kalman selection works substantially better than a Least Squares solution in a mobile vehicle when there are frequent satellite signal dropouts around bridges or high buildings, and gives improved performance around forested areas.

A Kalman solution uses the time history of the position and velocity it has created, whereas a Least Squares option does not use the time history. Trimble recommends using the Kalman filter for most operations. Select Least Squares for non linear movement such as on a suction cutter dredge. The Least Squares option is available for rare cases if you decide to trial it.

Signal Tracking Bandwidth – Allows for a DSP (Digital Signal Processor) selection for Wide or Narrow band tracking. The default is Wide band.

• Wide – Used for high-dynamic applications to allow the signal tracking to compensate for a higher rate of change in the Doppler frequency caused by antenna movement.

• Narrow – Used in low-dynamic applications where only relatively small changes in Doppler frequency are expected from antenna movement. Narrow bandwidth signal tracking allows less noise to pass through the filter to improve low-dynamic positioning with better accuracy.

Receiver Motion (Dynamic model) – Set to operate as a static or kinematic receiver. This mode determines if the receiver is Static or Moving for base station applications and OmniSTAR initialization. If set to Marine, then VTG Configuration options are available in the NMEA I/O Configuration page. The settings help reduce the velocity ‘noise’ when the vessel is alongside the jetty or otherwise expected to be stationary.

Receiver Motion (Dynamic Model) – As an aid to the Autonomous/Differential engine, you can select a dynamic model which best describes the dynamic environment for positioning. Select Marine when:

• Using a dual-antenna system outputting Rate of Turn to an application as this gives improved accuracy for that data. See NMEA-0183 message: ROT.

• Whenever a vessel is underway with a constant velocity.

• When a vessel is alongside with zero velocity. See NMEA-0183 message: VTG.

Horizontal Precision – The required horizontal precision that you set. This threshold determines when the horizontal quality indicator on the receiver display switches from flashing (precision threshold not met) to not flashing (precision threshold met). It also determines when an OmniSTAR solution has initialized.

Vertical Precision – The required vertical precision that you set. This threshold determines when the vertical quality indicator on the receiver display switches from flashing (precision threshold not met) to not flashing (precision threshold met).

RTK Propagation Limit – Defines the maximum age of the corrections, in seconds, which the RTK propagation will extend to. Values are selectable between 10, 20, 40, 60, or 120 seconds. When this maximum age is exceeded, the position solution will switch from RTK to DGNSS, SBAS, or Autonomous.

 

DGNSS Age of corrections – Defines the maximum age of the corrections, in seconds, for each constellation. When this maximum age is exceeded, the corrections are not used in the position solution. The solution will switch from DGNSS to SBAS or Autonomous.

Position Output Source – Only available when the receiver is in Heading operation mode.

• Derived – By default, the receiver outputs the position derived from the Moving Base receiver position plus the Moving Base vector.

• Native – The Heading receiver outputs a position that is not derived from the incoming Moving Base CMR corrections, but the next most accurate position such as OmniSTAR or an SBAS or autonomous position.

 

For Trimble RTX-capable receivers, running firmware version 6.20 and later, the following menu items are available:

ITRF Realization (2020)

Epoch – The default is Fixed.

• Fixed means ITRF2020 (2005.0 Epoch). Fixed to an epoch means that a point surveyed at different times will use the same transformation and result in the same position irrespective of any movement in the tectonic plate during the time interval.

• If Current is selected, then the latitude, longitude, and height are determined on the ITRF2020 reference frame for the current date accounting for any movement in the tectonic plate. The same point surveyed at different times may use different epochs in the ITRF Realization (2020) and result in different positions depending on the movement of the tectonic plate.

Apply ITRF Transformation to – RTX selection is the default setting. If None is selected, the RTX position is computed on the ITRF2020.

ITRF Epoch – This field cannot be edited and shows you that when Fixed Epoch is selected, then the 2005.0 Epoch is used.

Tectonic Plate – When the Current Epoch default setting is used, the receiver uses its position and automatically determines which tectonic plate it is on. The Auto setting is default. If the drop-down menu is opened, the selected plate and the four closest plates to the receiver position are listed. The Fixed epoch allows you to select another adjacent tectonic plate.

Recalculate – Click this button to force the current position of the receiver to be used to recalculate the selection of the correct tectonic plate. This button can be used when the Tectonic Plate is set to Auto. Other than at receiver power on, the receiver firmware does not continuously update the Plate selection if Auto is selected.

Click OK to apply the changed settings to the receiver.