A few more details about the search and the lost father and kids are in this article:
Happy end to massive search of Congaree National Park .
Gurtler, who has worked at the 27,000-acre Congaree National Park since 2009 and knows the terrain, advanced slowly on foot, his flashlight a dab of brightness in an ocean of black.
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The area had been searched before but, officials said, Gurtler just had a sense he should go back. “I gave a holler out every two, three minutes. I would walk 100 yards, give a holler, walk 100 yards, give another holler,” Gurtler said. Around 5:30 a.m., he heard a distant answering cry.
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Beginning Saturday night, the search-and-rescue operation by Tuesday had involved more than 80 people from 10 local, state and national agencies. It melded boots-on-the-ground woods savvy from Gurtler and others as well as a sophisticated military-like operation that coordinated land, river and aircraft search efforts. A team of rangers who came in from the Great Smoky Mountains National Park organized state and local rescuers ....
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Rangers closed the park to the public Monday, and clearing the trails helped in the search because it quietened things down.
Making the search more difficult was the fact that Kimbler and the children were wandering around instead of staying in one place. That meant searchers could cover one area, only to have the Kimblers wander into that area.
A good search management will try to combine local knowledge of the terrain, profiles of the subject, good organization and search technique, and as many resources as can be had. According to the article, when located, the father and kids were about 2½ miles from a visitors center. The terrain was very thick, with brush and lots of down trees, and a maze of small trails. Finding someone who is moving can be really difficult. As is typical in these cases, the search subjects hadn't gone all that far.
The article also says that Gurtler has participated in 11 previous searches this year. As noted up thread, the vast majority of searches are short affairs that are wrapped up in a few hours. Someone is reported missing, a couple of hasty teams walk the obvious routes, and quickly find the person. No big deal, and they rarely make the news. A few, like this one, get big and complex.