Resting place to hundreds of historical figures, Highgate Cemetery is known all over the world - but not everyone here is famous.Amongst this growing sea of ivy are thousands of headstones - some that haven't been seen in years.For many, this is what makes Highgate beautiful. But finding relatives' graves here can be tricky.Well, today some of them are being rediscovered through a process of careful clearing, which tries to keep the character of the cemetery.The ivy has been removed from some of these headstones - not only to protect them from decay - but also to allow them to be mapped digitally for the first time.This is Pete. His backpack uses lasers, which can't be seen, to take three hundred thousand measurements a second.It also has five cameras taking pictures constantly. The information is uploaded online, and eventually a digital map comes to life.