Real-Time and Post-Processing Differences

Alignment During Post Processing

Alignment in post-processing softwares is essentially the same as with the real-time INS. A notable difference is that post-processing softwares can process in the forward time direction (moving forward through the data, as it was collected in real-time) AND in the reverse time direction (moving backwards through the data, opposite to how it was collected in real-time). Forward and reverse processing solutions can then be combined, and their combined result is better than if just one processing direction was used. Thus you will notice on the flight plan diagram shown above that there are kinematic alignment maneuvers performed at the beginning and end of the flight:

This ensures both processing directions have a proper kinematic alignment maneuver at the "beginning" of processing, however the real-time INS solution does not improve with the addition of an alignment maneuver at the end of the flight.

Forward and Reverse Processing

The larger implication of forward/reverse processing capabilities is that all INS initialization processes (static period, alignment, figure eights) should be performed at the beginning and at the end of the flight, thus missions begin to take on a symmetrical pattern:

1. Static period

2. Kinematic alignment

3. Figure eights

4. Mapping mission

5. Figure eights

6. Kinematic alignment

7. Static period.