RTK Engine

The RTK Engine module takes the receiver observations and processes either baselines (if in Baselines mode) or station positions (if in VRS mode) to determine and pass on high quality coordinates for a given set of stations in your network. It should be used,

if very fast reaction (real-time) together with medium accuracy is required,
and either if the baseline lengths within the network are of small to medium size (not longer than 35 km),
or if corrections can be made available from a VRS network that covers the stations monitored with the RTK Engine.

Note - In Baselines mode, the RTK Engine does not compute baselines longer than 35 km, since results of longer baselines are not reliable and accurate enough. This restriction does not apply to the VRS mode.

The RTK Engine is located below a Synchronizer module that outputs synchronized receiver observations. The number of stations processed therefore depends on the stations selected in the Synchronizer and on their availability. The RTK Engine uses satellites above an elevation of 10° and predicted orbits, if these are made available by the Ephemeris Manager module. It can run in parallel with other processor modules.

Adding the module

When the module is being added, the RTK Engine Properties dialog appears. It lets you define and select module configurations. Each configuration holds information on the processing parameters, such as the processing mode, a maximum baseline length and the usage of redundant baselines (over-determination) for baselines, or the connection to the correction data for VRS mode. You also may remove a configuration from here, if you do not need it anymore. You can change the settings of the selected RTK Engine configuration at any time, but changing the settings restarts the calculation of the affected baselines.

Processing

The RTK Engine module supports two processing modes, the Baselines and the VRS mode.

Baselines mode:	When starting up, the RTK Engine scans the network for all stations made available by the Synchronizer and defines, starting with the most central station, baselines between the stations based on their known positions. During runtime, it determines the current positions from the observations for all baselines.
VRS mode:	The RTK Engine module connects to a specified VRS correction data stream to compute VRS solutions for the available stations. Thus, the current positions are determined.

The module calculates the position offsets (DN, DE, Dh, D 2D, and D 3D) and their 3-s errors. If the known positions of the stations are periodically updated to the current epoch due to known velocities, the processing re-starts with the new positions.

You can apply several filtering methods with user-specified settings to remove outliers and to smooth the position estimates.

Resetting the calculations

To restart the processing of the network select the module shortcut menu command Reset All Baselines (or Reset All Stations, if in VRS mode). For resetting selected baselines or stations go to the RTK Engine Processing Status module view.

RTK Engine in Baseline mode: What happens, if one or several receivers are not available anymore?

If you disable a station at the Synchronizer, the RTK Engine creates new baselines from the changed network design, compares the new set of baselines with the previous one, and restarts computing positions and their errors for the new baselines. At the RTK Engine Processing Status view, the baselines to or from the removed station still show up in the list, but display Paused in their Status columns.
If a station is available in the Synchronizer, but happens to output no observations for a specific receiver (for example, the receiver is currently disconnected), the RTK Engine keeps the baselines for 60 seconds and continues determining positions for them. At the RTK Engine Processing Status view, the baselines to or from the respective station display No observation available in their Status columns. After 60 seconds, the Synchronizer does not wait anymore for observations from this station; the RTK Engine then reacts as if a station has been disabled at the Synchronizer. When the missing station recovers, the original set of baselines is created again.

Output of results

The results of the estimation process are displayed in numerical form at the RTK Engine Processing Status view. You can configure the Alarm Manager module to trigger alarms, if any station has lost fixed solutions. In combination with the Integrity Monitor module, additional alarms can be triggered if offsets or errors exceed specified thresholds.

The RTK Engine makes the results of its estimation process available to depending Integrity Monitor modules.

Tip - Use the Integrity Monitor module to display the offsets between the known coordinates of a station and its estimated position in numerical and graphical form. Using the Integrity Monitor module for the RTK Engine in Baselines mode you can also hold one or more stations fixed and thus perform an adjustment on the estimated positions of the unfixed stations. The resulting positions and maps refer to the adjusted coordinates.

Logging into the database

The RTK Engine module writes the positions of fixed solutions for all stations into the central database. The database contains the following tables referring to the RTK Engine system:

Table name	Contents	More information
MeanPos_RTKEngine_<config name>	Position vector and covariance matrix components; DOP, and number of satellites.	One row for each epoch and each baseline. *
MeanPos_RTKEngine_Filtered_<config name>	See above	Positions depend on applied filter. *

*By default, the data of these tables is reduced depending on settings of the TableLifeTime table.