My experience in this area is somewhat dated, about twenty years ago for really extensive work. We (Southern Arizona Rescue Association and Pima County) did a controlled study evaluating the POD for various subjects in a desert environment. Our main finding was that passive subjects, even plainly exposed in the open, were far less likely to be seen than actively signaling subjects. Even in best case scenarios, there was an uncomfortably high likelihood that the victim could be missed. Basically, we never downgraded an area until it had been air and ground searched. In the end, so much depends on the vigilance and concentration of searchers, both aerial and ground.

I would argue that there is no solve all resource and circumstances always change. I recall a search for a young boy (about nine). About midnight, I learned that the kid had been in a school class to which I had given an outdoors survival presentation about a month earlier. Talk about personalizing the operation!

Anyway, we found our lad early the next morning in an area quite capably searched the evening before. He had listened to me - when night came, he found a small rock shelter and was sleeping away when the team came through. He had woken up when the next effort came through. I always thought dawn after the first night was the "Golden Time." Visibility returns, everyone starts stirring, and people find one another.

Implications for seach strategy - immediately deploy teams, and go all night, or at least get into the search area and take a quick nap. Plan for new crews to hit the field right at first light and really hammer hard. This is also a really good time for air operations. If 10 AM comes and goes, you may have an epic on your hands.