Photogrammetry

To fulfil a client objective, Vocean  developed an ROV mountable  Photogrammetry imaging system,  shown  above. An array of four cameras  ensures the required overlap between images in the horizontal plane. For a vertical surface like a tunnel wall, the   cameras are perpendicular to the viewed plane.   The cameras are mounted on a tilt mechanism which allows  the cameras to be perpendicular to the ceiling and floor surfaces as required.  This provides great flexibility in operations  over a fixed frame solution which would necessitate ROV recovery  to re align the cameras to the appropriate surface. Tilting the cameras on the fly greatly  improves efficiency.

A proprietary user interface in the control room allows the operator adjust the camera parameters individually to suit the  visibility and light level.  Adjustments can be evaluated directly via video feed from each camera.  Stills recorded are transferred to the control room server directly. Thus they may be accessed during the survey to ensure image quality is achieved.

Output

  • 3D mesh files
  • 3D textured files – photorealistic surface on 3D Image
  • Fly around video
  • Virtual ruler dimensioning, linear
  • 2D area dimensioning
  • 3D volume calculation
  • 3D printed model (surface colour print texturing)
  • CAD compatible files for further processing

Case Study

  • To investigate a suspected crack and if it is a crack, determine the depth
  • Location is the inside wall of 2M diameter steel pipe
  • Hydrostatic pressure at location equivalent to water depth in excess of 300M

Challenges

  • Withstand the hydrostatic pressure
  • Provide adequate lighting without creating shadows
  • Ensure correct camera settings for the light conditions

Solution

  • Simple solution – Parallel laser lines to scale crack depth by parallax
  • Digital photogrammetry – Create a model of the ‘ crack ‘. Virtual fly-around videos below show the area very clearly.   The virtual ruler allows sub-millimetric measurements.

Gallery

Submerged Aircraft – Cockpit area

Submerged Aircraft –  Helicopter

Submerged Aircraft –  Engine nacelle turboprop passenger plane