Some time ago there was some discussion of modeling everything FWF and
3D digitizers to accurately measure the complex dimensions of some of
the pieces that must go under the cowl. I vaguely remembered a process
involving photography to accomplish that end. That process involves
taking a picture or a series of pictures and then computing whichever
coordinates you are interested in. At that time I couldn't bring up the
technical word. Today, that word popped into my mind. It is photogrammetry.

Has anyone any information on the mathematics involved?

The motivation for all this is as follows. It seems to me that modeling
the bits and pieces that go under an aircraft cowl would be made much
simpler if we could simply take a series of pictures of the gadget to be
modeled, feed the resulting pictures to the computer and get accurate
coordinates of the said gadget, preferably in a machine readable form.

Doc Custer
Retired software engineer and sometime Audiologist
Building RV9-A. Fuselage

You can do that in Rhino Doc. Under "View" move down to
"Background Bitmap" and select "Place". Choose a jpg as
your back ground. You can then scale it to the proper
size knowing only one dimension. That is exactly what I did
here using the dimensions Mark sent me.

You then have to make the other measurements you are seeking
manually.

Paul Lamar ...No rotor no motor.

I understand.

The few pix I saw used for photogrammetry used a gadget with 3
calibrated orthogonal legs. By measuring the apparent length of the
legs it is possible to come up with a mathematical transformation to
measure anything shown in the pix to some reasonable error. This
process also handles parallax. If you have enough of the gadgets it
will even correct for some of the optical errors.

In land surveying, they use 3 or more known locations showing in the
aerial photo to come up with the coefficients necessary.

Doc Custer
Retired software engineer and sometime Audiologist
Building RV9-A. Fuselage


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