I Live at the foot of a hill in North Wales. At the top of the hill are disused slate quarries I decided to use the Waypoints 2 feature by plotting a route over the quarry. Studying online os maps also showed a small pond just a few hundred yards over the back of the quarry I thought I would investigate this as well. This would mean flying a few mins out of visual contact but as this was open moorland with no roads or properties I thought the risk was worthwhile. I sent the drone off and at the point were it diverted to view the pond I lost connection no video. I was not unduly concerned as waypoints was set to continue in such events. The drone reconnected a few mins later and I returned to home point. But on reviewing the recorded video It shows how lucky I was to not at least have a long steep walk or it could have landed in the pond never to be seen again!!! This happened because the I misinterpreted the altitudes of the crucial waypoints and was low by over 150 ft All altitudes in Waypoints are heights above “home” so waypoints need adjusting to allow for this. Google Earth produced much more accurate figures. The edited video link a least proves the sensor system was extremely good!!