Original article can be found here: http://www.caa.co.uk/Blog-Posts/Guidance-for-flying-drones/
Whether you are flying a drone for fun or profit you must legally keep your device within your 'visual line of sight' at all times. The law is based on the clear premise that if you can't see your drone, you can't control your drone. For guidance we put an actual measurable distance on this 'line of sight' - which is set out very clearly in our Drone Code.
How high can you fly?
So, to stay safe you must simply fly your drone no further than 500m away from you horizontally or 400ft above you vertically. That sounds fairly straightforward to achieve, particularly if your drone gives you a distance data reading on your screen telling you how far the device has travelled from its transmitter. However, we do know that some users are flying higher than they should, so it's very important to understand how high 400ft really is to ensure you stay legal and don't inadvertently fly into airspace where a drone shouldn't be. As a comparison, the London Eye is 443ft, Blackpool Tower is 518ft and the Spinnaker Tower on the Portsmouth waterfront 560ft. Of course, drones must be kept well away from all structures, as well as built-up areas in general, but if you can visualize any of these landmarks then you know that you need to keep well below their highest point. Of course, manned aircraft can fly lower than 400ft, particularly helicopters, so it is vital you still keep a good lookout.
The same rules apply to first person view technology
First person view (FPV) allows the operator to get a bird's eye view from the drone itself as it relays live footage from the on-board camera to either a handheld screen or special goggles. This activity, while a lot of fun, does not allow you to fly beyond your 'unaided' visual line of sight. As you are not really physically located in the drone, you, or a friend, still have to be able to see it from the ground! Ultimately, if you think you are flying too high, or are pushing the boundaries, then you probably are. There are no excuses for sending your drone near to an aircraft either deliberately or accidentally. Drones offer great potential and can clearly be a lot of fun, but often attract headlines for all the wrong reasons. As the drone community grows it is in everyone's interests to promote responsible and safe use of this exciting new technology. We want to make sure drone users are flying their devices sensibly and sticking to safe heights and abiding by the rules at all times.
The height limits for flying a drone are clear. Stay low and stay safe.