I know next to nothing about photogrammetry except to know that it’s a lot more complicated than anything I or anyone else has tried to use in this thread to reconcile the difference in opinion about the diameter of AE’s tires. That’s why I posted earlier the link to
the video that shows perspective playing such a large role in complicating the determination of the relative size of two objects in a single photo. Then
John Kirk pointed out the role of “tire squat” in complicating any comparison with the tire
diameter versus the height of a 55-gallon drum (which, incidentally, is cited to be both 33.5” and about 34.5” in the same
Wikipedia article).
Many such critical considerations (can you say “trompe l’oeil"?) come to mind: How high is the camera above the ground? Is the ground level? That is, is the photographer standing on a small rise or in a slight depression, so that the lens may not be in the same plane as the objects being compared? Are the two objects being compared equidistant from the lens? Are shadows distorting important detail? What are the lens characteristics of the camera? And there are myriad other considerations that require the expertise of a person like Jeff Glickman to investigate and reconcile to obtain a reliable answer. After all, how much time and energy went into trying to
measure the length of AE’s shoe by comparing it to the rivet spacing on the aircraft?
That said, I’m just as intrigued as others with this matter of tire size, and cannot hold back in trying to apply my own amateurish hand and eye and naïve knowledge to the problem. It’s shaping up to be a lot like those witness accounts of a crime that differ substantively, leaving it to a jury to choose.
Let’s take the two pictures below for comparison purposes. The first one shows a Lockheed 10A at the New England Air Museum (NEAM) and is from
Earhart Project Research Bulletin #58. As has been remarked in this thread, the tape measure shows that this tire is clearly 28” in diameter — well, except for
one person, who assures us that the tape measure gives the tire’s indicated diameter to be 30”.
No, I say that museum tire is indeed 28” high: the photographer has used the détente on the measuring tape to lock it with the marking for 28” showing at the very bottom of the visible tape. But I see the first 2 inches of the tape extending up above the horizontal plane across the top of the tire by two inches.
Why did the photographer extend the tape those 2 additional inches? Well, because the body of the case for the measuring tape is exactly 2”, and the two extra inches at the top come from the case’s two additional inches at the bottom. It’s likely that the photographer ran the tape out 28” so that the end of the tape touched the floor and the 28” marking was level with the top of the tire; then he set the détente and inverted the tape, standing the tape on its case as shown to take the picture, thereby causing the end of the tape to be seen to be 2 inches above the top of the tire. Either way, I say that the tire shown is indeed 28” in diameter — and certainly not the claimed 30”.
Notice two other things about that picture and the landing gear shown. First, the top of the tire appears to come about midway up that oval surface at the top of the fork. And second, there is quite a bit of space showing between the top of the tire and the mud guard. Neither of those would be affected by "tire squat."
Now look at the second picture, which is NR16020 being refueled in Bandoeng. I think that the two things I pointed out in the previous paragraph support the notion that this aircraft’s tires are of a larger diameter than 28”, perhaps even as much as 35”.
First, the top of this tire is showing significantly higher than the middle of the oval surface at the top of the fork. And second, there appears to be significantly less space between the top of the tire and the mud guard above it than for the plane at NEAM. Assuming that the fork assembly on AE’s plane is the same size as that of the plane photographed at NEAM, then the miserable little 3.5” of
radius that is consuming so much attention in this thread is easy for me to reconcile in my mind’s eye. But are those perceptions the result of varying perspective between the two pictures? There’s no telling. How to reconcile this difference in amateur photo analysis? Leave it to those trained in photogrammetry.
So, I continue to believe in the integrity and correctness of the
Aircraft Inspection Report that was signed the day before AE began the second world flight in her repaired airplane. I’m comfortable in trusting that the main tires were indeed of the 35” diameter size. But then, I keep hearing Ronald Reagan’s voice: “Doveryai, no proveryai – trust, but verify.” And I hope that the Bureau of Air Commerce inspector who signed that form (Lake? Duke? Dike?) did likewise.