If you're planning trekking somewhere off the beaten track far away from modern civilisation, such as Wales, then you'll want a GPS tracker, which will tell you exactly where you are on the planet. Use it to load in waypoints to guide you during walks, or output your wanderings to a computer to overlay on a map to confirm that you really did go around in circles. As a keen walker myself I am rather partial to my GPS (particularly because my mapping software has all the nearby pubs clearly indicated for that post-trek pint of ale by the fire).