I just watched the TIGHAR video of the helicopter tour of Nikumaroro again (for about the 10th time, but the first time in awhile). What strikes me is how much larger the island looks in the video compared to the Sat photo. It also convincingly shows how difficult it would be to spot someone on the ground even at the low altitude that the helicopter was flying.
I once sat through a presentation on human visual perception that was given by a ph'd researcher and former director of a lab at the Scripps Institute of Oceanography. I wish that I could remember his name, but his lab did some of the pioneering post-war research into this subject for the Navy. It was a fascinating presentation and he said that the part of the eye (the fovea) that is responsible for resolving fine details such as reading text in a book, or looking for cars or pedestrians when driving, is tiny and represents an area that is about the same size as the tip of a thumb when held at arms length. The rest of the eye is used for peripheral vision and is good at detecting motion but not at resolving detail. He went on to say that the way that humans have evolved to use the fovea is to constantly scan the eye around which is used to "stitch" an image together in the brain. One of the points that he made in his presentation is that while scanning or searching with the fovea, a significant period of time can elapse before the fovea covers a wide area and finds something of interest. One of his key points was that if the viewer is in motion (like flying in a plane) then large areas will not be scanned before it passes by. Psycho-perceptual factors can also play a role. For example, if there is something visually interesting (sort of like a false positive), the fovea may linger on that object longer than necessary at the expense of searching other areas of interest. Looking at the shoreline at Niku, it is full of visually distracting objects that would make it hard to spot a person on the ground. This is especially true when one considers that the apparent size of a person on the ground (after factoring in the angle due to the height of the plane) is probably no more than a few feet. It would be interesting to hear his perspective of the 1937 Lambrecht search, I'm sure that after watching the helicopter video that he would put the odds of successfully finding someone on Niku based on a 5 minute overflight at higher altitude at close to nil. If this is of interest to Tighar I can put out some feelers and contact him, he seemed to be the type that would be very interested in the research that TIGHAR is doing and I'm sure that he would want to delve into this.