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.
Dr. Custer,
Photogrammetry is used to measure more than digitize. We use it
to align
large radio telescope surfaces.
We have a MetricVision MV-200 laser radar which can digitize.
This
technology is faster and more accurate than photogrammetry but not
good for
outdoor applications. We have digitized objects up to 60m on a
side.
http://www.metris.com/products/laser_radar/laser_radar/
-Ben
Thanks Ben. Very Impressive. Probably out of my price range. :)
I was hoping that my posting would jog someone's memory and point
us
to some references. I was hoping we could gin up a PC application
that
would apply the appropriate transformations and give us reasonably
accurate results. The process would go something like this. Take a
photo of the subject with the necessary photogrammetry objects in
it.
Feed the result to a visualization or modeling program. Select the
points of interest, pass these points to the transformation program
and get the transformed coordinates back. All of this is just
hopeful
speculation. I know nothing of the complexities of photogrammetry.
One of the local land surveyors has a program with the ability to
input aerial photographs and produce accurate maps that meet legal
requirements. His program uses landmarks that have known
coordinates
to derive the transformation coefficients necessary to produce
accurate maps from aerial photos. Maybe we can make use of his
programs. I will go talk to him about it.
The motivation for all this is to be able to model a FWF
installation
with sufficient accuracy in order to:
1. determine the proper location for all the necessary gadgets
that
need to fit under the cowl with no interferences,
2. design a cowl that will fit the first time,
3. calculate weight and balance so as to determine the proper
location for the engine, and
4. design a mount for the engine.
All this without the need for a FWF mockup.
Doc
We have accurate 3D Rhino models of many of the parts Doc.
Just let me know what you need.
Paul Lamar
Doc, Paul does precisely this on a daily basis. How do you think
we
can make complex engine mounts without the engine or aircraft on
hand? Whether it is fitting a cowl, designing the radiator set up
or
making the engine mount, thanks to Paul and Rhino we are not
guessing
and we are not mocking up. I have on file a number of beautiful
drawings showing what your project would look like with the S-beam
engine mount. I am sure you have them to. They are not
approximations. They are the real deal. Jerry
-----------------------------------
I think you are missing a point Doc.
All the 3D's I publish and send intrinsically contain exact
dimensions.
They are all drawn to as an exact scale as I can achieve.
These are not cartoons or sketches.
Since I sent you all the original 3D drawing files on CD
on the RV9. All you need do is load them into Rhino and use
the dimension command to find out what they are.
There is a revolution going on the manufacturing world.
3D drawings, like those from Rhino and Solid Works, are loaded into
other programs like SurfCAM and MasterCAM where NC machine tool
programs are generated to manufacture the parts. Only in the
case of checks or problems is it necessary for human readable
dimension on paper or the computer screen. Paper 3 view drawings
with dimensions are no longer used.
Having said all that dimensions are available on request.
Paul Lamar ...No rotor no motor.
I understand that Rhino models include the dimensions. A long time ago
I was the software development manager for one of the leading CADD
drafting and design firms. We did one of the early 2 and a half D
punch press CAD CAM interfaces to Westinghouse's existing punch
presses. Knocked their socks off! Simply do the design, and out comes
the tape to drive the punch. They couldn't believe it until they saw
the machine work. Now Rhino and the others knock my socks off!
There is a whole world of artifacts that we do not have access to a
ready-made model. My interest in photogrammetry lies there. See the
previous post.
I am truly sorry if I offended you or Jerry. I did not intend to. I
admire your and Jerry's work greatly, as I have said in the past.
Doc Custer
Retired software engineer and sometime Audiologist
Building RV9-A. Fuselage
Naw! I am growing a thicker skin :)
Paul Lamar ...No rotor no motor.
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