Real-time comparison of flight plan corridor vs actual flight path

I am looking for advice on how I might go about doing a real time (or as near to real time) comparison between the flight plan and the actual flight path.
The flight plans will be corridors(I know QGC can do) taking imagery. There is a width (distance way on either side) from the center of the corridor that the fixed-wing can be in to capture the required imagery.
I would like to be able to see that the aircraft stays within that corridor and if it gets outside that width of the corridor it will display that as it has missed that section of the corridor. Essentially displaying feedback to know if a section needs to be re-flown before the missed section is caught in the data review process.