Daniel Kish has been blind since he was a baby but that hasn't stopped him living an incredibly active life that includes hiking and mountain-biking. To do this, he has perfected a form of human echolocation, using reflected sound waves to build a mental picture of his surroundings.
When Daniel Kish clicks his tongue, the world answers back.
Cars, trees, doorways, bollards on the pavement… all are identified and mapped in his brain using information gleaned from a series of sharp little taps of his tongue against the roof of his mouth, two or three times a second.
From an early age, the Californian developed a sonar technique which allowed him to navigate using echoes from repeated tongue-clicks. The skill has led to him being dubbed a "real-life Batman" - a description he welcomes.
