More Than One Orthophoto

Pre-Restoration Scan

Recently we acquired a very rare WW2 vintage torpedo motor from Deeper Dorset‘s very own Grahame Knott. The motor is unusual; instead of the typical 4-cylinder radial configuration this example is an experimental 2-stroke 8-cylinder radial engine. As far as we know the engine was never put into production, but there are a few documents waiting at Kew for a deeper read into the history of this beast.

Screenshot of the torpedo motor in Photoscan Pro. Note there are two chunks of the same model: one version for Sketchfab (5.8M face, lower res) and a much higher resolution example (22.3M faces).

A Runner

The plan is to restore this engine and to hear it run again. This is no easy task. Whilst the engine is complete the ancillary equipment appears to be missing, with possibly just one of a pair of fuel pumps remaining. But before we start pulling it apart, the first step is to create a 3D model of it:

The model will serve as a great reference for when its time for reassembly.

Multiple Orthophotos

For a while its been possible to have more than a single orthophoto in Agisoft Photoscan Pro. Sites like the P-47-D crash site really only need a single orthophoto so using this feature was not really necessary. But the radial torpedo engine does, and this is how:

  • Create the model, scale and reference as needed.
  • As the model has no GIS, we use planar type of orthomosaic:

The dialog box used to create an orthomosaic – note we use planar type for objects like this.

Planar types have several methods to set the view required. Having aligned the model on screen “Current View” is a quick option.

  • With the first orthomosaic created, select it and then on right mouse click – Duplicate.
  • This creates a second copy. It can be handy to start to give the orthomosaics relevant names.
  • The copied orthomosaic becomes the Default. The next step will discard this copy, but do not panic when it disappears.
  • Orientate the model to a different view and then run through the steps to create an orthomosaic.
  • Repeat the copy/rename/orientate steps as required.

Instead of deleting the single and default orthomosaic Photoscan Pro will append the new examples:

Each new orthomosaic is appended to the list of available.

Detail for Reassembly

When it comes to putting the motor back together the resulting orthophotos will be printed and hung on the garage wall. These will serve as a reminder as to where all the bits go – far better than memory alone can.

Side view of the motor, with No1 cylinder near centre of the image.

Auxiliary drive view of the motor. The cardboard (top right) is blanking the air inlet.

A view of No5 cylinder. Knowing where the fuel pipes run (centre frame) will probably save hours of head scratching when reassembly commences.

Summary

This is a great tool for not only creating a record of the motor before restoration but will act as a guide for reassembly when ready. It saves taking and cataloging images as it comes apart, or (worse still) trying to figure out where parts went.