Post Processing Engine

The processing of stored observation data with arbitrary session length results in highest-precision coordinates and is preferable, if the time to react to the measurement is of less importance. The Post Processing Engine module takes stored raw receiver data, such as files in RINEX, DAT, or T01 file format, and automatically estimates positions from baseline combinations with overlapping time sequences. It should be used, if the baseline lengths within the network are of arbitrary length. For obtaining optimum results, the longer processing periods should be covered the longer the baseline are. The processing results are passed on to dependent modules for filtering, adjustment, and data display. The Post Processing Engine works in two modes, static and kinematic.

The Post Processing Engine uses dual-frequency GPS and GLONASS observations from satellites above a specified elevation and predicted orbits, if these are made available by the Ephemeris Manager module.

Adding the module

The Post Processing Engine module is available from the Tree view root Trimble 4D Control Server. Trimble 4D Control Server accepts multiple Post Processing Engine modules in the system.

When the module is being added, the Post Processing Engine Properties dialog appears. It lets you define and select module configurations. Each configuration holds information on the processing mode, the data sources, the time segment to be processed, outlier filtering, and processing parameters. You may remove a configuration from here, if you do not need it anymore. You may change the settings of the selected Post Processing Engine configuration at any time.

Network definition

Set up the network for post processing using the list of reference stations defined in the system. There is no necessity for the stations to currently be added to the Device Manager module.

The baselines between stations are newly established for each session.
If the Post Processing Engine cannot find session data of the specified period for a selected station, no baseline connecting to this station will be established.

Processing

The Post Processing Engine scans a specified folder and its subfolders for observation files of a specified period and creates a set of independent baselines from the available data. This scan is repeated in specified time intervals.

When a session starts, the Post Processing Engine scans a specified base folder and its subfolders for observation files of a specified type (including zipped files) and defines baselines between the stations based on their known positions. During runtime, it determines the current positions from the observations for all baselines and compares them to the known positions.

With the static processing mode, each session results in one position per baseline.
With the kinematic processing mode, each session results in multiple positions per baseline: One position per epoch.

Note - Since kinematic post processing results in a high number of values and is a memory-consuming process, the module internally sets limits to the number of stations and the session duration, if the kinematic processing mode is selected.

The Post Processing Engine calculates for each position the baseline components (dx, dy, dz), offsets from the known coordinates (DN, DE, Dh, and D 3D), and errors. Of course, the processor respects antenna height offsets. 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.

Stopping and continuing the process

Use the module's shortcut menu to stop and continue the post processing. The module icon displays the process status:

	The module is active and will be scanning folders, establishing stations and post processing, when a session is due to start or is currently doing so.
	The module actions have been stopped.

Output of results

The results of the folder scanning and the results of the last and previous estimation processes are displayed in numerical form at the Post Processing Engine views. You can configure the Alarm Manager module to trigger alarms, if any baseline has no fixed solution. In combination with the Integrity Monitor module, additional alarms can be triggered if displacements or errors exceed specified thresholds.

The Post Processing Engine stores the results of its estimation process to the database. Thus, they are available to depending Integrity Monitor modules. From the Integrity Monitor module, external devices can request positions for selected baselines and receive them as NMEA strings.

With the static processing mode, the Processing Engine stores one epoch per session to the database.
With the kinematic processing mode, the Processing Engine stores the results for each epoch of the session to the database. The depending Integrity Monitor module, therefore, receives multiple positions offset and error values per session and per baseline.

Note - Use the Integrity Monitor module to display the offsets between the known coordinates of a station and its estimated position (displacements) in numerical and graphical form. Using the Integrity Monitor module you can also hold different or additional stations fixed and thus perform an adjustment on the estimated positions of the unfixed stations. In this case, the resulting positions and maps refer to the adjusted coordinates.

Logging into the database and Reporting

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

Table name	Contents	More information
MeanPos_PostProcessingEngine_<config name>	Position vector and covariance matrix components; fixing status, coordinate type, DOP, and number of GPS/GLN satellites	One row for each station. *
PostProcessingHistory_<config name>	Session and event times ; position vector and covariance matrix components; coordinate type, DOP, and number of GPS/GLN satellites	One row for each session and each station. Session time is the last epoch of processed period.

Table name

Contents

More information

MeanPos_PostProcessingEngine_<config name>

Position vector and covariance matrix components; fixing status, coordinate type, DOP, and number of GPS/GLN satellites

One row for each station. *

PostProcessingHistory_<config name>

Session and event times ; position vector and covariance matrix components; coordinate type, DOP, and number of GPS/GLN satellites

One row for each session and each station.

Session time is the last epoch of processed period.

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

To create reports from the Post Processing Engine module's data, use the Trimble Report Generator application selecting the Post Processing Engine IntegrityManagement report type.