3D Scanning of Aircraft Repair using Photogrammetry

GOM Photogrammetry AircraftPhysical Digital, based in UK, were recently requested to complete the 3D measurement and inspection of the repaired area of a twin engine turboprop aircraft.  Using a GOM Photogrammetry and ATOS optical scanning system, Physical Digital engineers carried out the ‘dent and buckle’ inspection on-site at the airfield.

The project remit required measurement at customer site and provide measured data to aerospace accuracy and traceability; the following steps and systems were used to complete the project:

The GOM TRITOP photogrammetry system uses multiple images captured using a high resolution DSLR camera to precisely and accurately triangulate the position of reference points in 3D space.  Coded reference markers are used to orientate the images together, which subsequently position the un-coded markers in a point cloud.

Photogrammetry scan dataCalibrated optical scale bars were used to define the relative size. An understanding of accuracy was achieved by comparing the value of the scale bars to the captured lengths.  The deviation for the photogrammetry for the project was 0.006mm which demonstrated a much greater degree of precision than the tolerances demanded by the customer.

The optical scanning system used the photogrammetry point cloud to calculate its position on the airframe of the aircraft.  Using a blue light projector and two high resolution cameras, the GOM Triple Scan sensor projects a phase shifting fringe pattern onto the surface of the object. The cameras capture several images of the projected pattern and calculate millions of points which, when combined with adjacent data, produces a high resolution point cloud.  For this project a measuring volume of 700mm was used to capture a large area with a capture point resolution of 0.18mm.  Several scans were required to capture the area but due to the speed and accuracy of the GOM system Physical Digital were able to scan the required area within a short timeframe.

scan-dataTo complete this project it was necessary to compare the left hand side geometry of the airframe against the right hand side to inspect for the quality of the repair.  Using the GOM Inspection software, the right hand side could be mirrored along the centre line of the global coordinate system and then inspected against the scan data of the opposite side.

A colour map of the selected area was produced and referenced against the required tolerances.  From this, a detailed inspection report was produced indicating that the repair was completed within the required parameters.

The project was conducted under a significant time constraint as the client wished to return the aircraft back into service within the shortest time possible.  The full 3D scanning and inspection process was completed at the customer site within the time scales set by the client and the aircraft was able to return to service.

Physical Digital provided traceability for the measurement through the ATOS Professional and GOM Inspect software. All measuring data is held in the software allowing vital information to be recalled at any time.

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