When I was walking along Hadrian's wall I saw a guy in the distance who was setting up three tripods and then taking photographs of the wall from each before moving on.  I watched him for a while and wondered. We got closer and eventually our paths crossed. I could see he had some other devices there I had not seen before and assumed they were storage of some sort.
I had to ask what he was doing.

Well it turns out his job was to walk the length of Hadrians wall and take photographs from all angles with satellite reference points. He was working for a company producing a digital 3D map. 

"Wow what a fantastic job"  I said.  
"It's OK I suppose but I've gotta walk along this  ***** wall"

We chatted for a while and it appears the company he works for does the same for significant landmarks all over Europe .  I asked if they had any jobs

 

And every one said, 'If we only live,
We too will go to sea in a Sieve,---
To the hills of the Chankly Bore!'
Far and few, far and few, Are the lands where the Jumblies live;
Their heads are green, and their hands are blue, And they went to sea in a Sieve.

Edward Lear
http://www.nonsenselit.org/Lear/ns/jumblies.html