How-to Computation Trigger

Kalman/Skew

For more information on triggering when kalman is active, please see:

This document will describe how to trigger your computation setup. The definition Trigger will be used throughout the Qinsy Computation, where each instance will have a different effect.

Trigger system

The triggering system is used to initiate computation cycles that calculate positions for all of the nodes in the adjustment in each cycle. The data output rate of the selected system determines the initiation rate of the computation cycles.

For example, if a positioning system is selected with an update rate of 1Hz, the computation update rate is 1Hz too; data output at 10Hz results in 10 computation cycles per second.

Selection is either here from the drop-down menu

Or alternatively, a selection can be made by enabling a system in the middle pane and activating 'Use this system to trigger the computation' in the System Parameters in the right pane.

Normally a positioning system (for example a GNSS receiver, or USBL for underwater systems) functions to trigger the computation cycle.

This means that when new raw positioning data is received, the computation of the object position and corresponding nodes is started. At the time of computation, the position, rotation values, heading and height of the object are calculated.

Computation trigger

NOTE: Per computation only one trigger system can be selected

NOTE: At present, positions from other positioning systems are not skewed to triggering time! (meaning when triggering on USBL observation the vessel vessel position isn't skewed to this observation time)

Trigger system (GNSS/USBL)

When the triggering system is set to the GNSS system and the GNSS system is receiving an update. The last received dx, dy, dz from the USBL system will still be applied.

However triggering on the USBL will use the current dx, dy, dz of the moment it triggers the computation. Example below where 3 computations are setup:

Vessel (trigger on GNSS)
ROV (triggered on USBL), where the SSS beacon is disabled;
SSS (triggered on USBL), where ROV beacon is disabled

Each Computation in that case, will only be triggered when it receives an update of the selected observation. In the case of the USBL system the ROV position will only update when its own beacon outputs and same goes for the SSS object. This will make sure it will keep using the current dx, dy, dz of the moment.

Magnetometer Generic Export

When trying to export Magnetometer data (or any underwater positioned object) at a 10hz interval, which was triggered online at a lower update frequency

Make sure to enable 'Deskew' in the Generic Editor, which allows for interpolation of position updates.

Trigger Rate

Until recently, the internal structure of the adjustment code meant every update of the triggering system resulted in a Qinsy computation cycle. This was not a problem as typically the triggering system was, and still is in many cases, either a Positioning System (GNSS system) or a USBL system, which output data at low rates.

However in case of an inertial navigation system, the positioning data is combined with the attitude data in a single telegram at for example 50Hz or 100Hz. In such a case, the computation cycle is initiated at an unnecessarily high rate. By setting the maximum computation trigger rate to, say, 10 Hz, the computer CPU load is reduced without negative effect on the data results as well as read/write to the hard disk.

Note that this setting does not affect the attitude data which is still acquired at the higher rate

Use the option 'Max. triggering rate' (below) to lower the number of computation cycles.