when you go on google earth and hover your cursor over a point like consett you can read off at the bottom longditude latitude and height above sea level consett is just below 1000 ft but if you look on derby arona site there is a bit on pigeon gps mapping you will see that birds were liberated on mount tide and flew no problem.some groups would not go through the cloud and flew out to sea at high altitude to area where no clouds before desending and returning to island,and some groups dived through the clouds at a fast pace, worth a look.birds liberated at 25,000ft.