In the Pacific Northwest it quite common for Loggers to string cables with great rapidity and not all of them find their ways into NOTAMS.
In some rather inclement weather I passed up and over the mountain ridge and spent two hours at our Mill then loaded up and started back to home.
As I descended from the top of the ridge using the exact same route I had used just a few hours before...due to some upslope fog/cloud I deviated over to the edge of the canyon and whizzed across the top of a newly erected high lead logging line. Ironically, I was flying the same type and model of the aircraft in this accident.
Lady Luck smiled broadly upon me that day! Had the canyon been clear of fog and cloud I probably would have struck the cable as they are very. hard to see especially when you think there are none around where you are flying as you are not actively looking for them.
This stay 500 feet ago works but it should mean 500 feet above the potential obstacles.
500 feet above the Ridgeline heights would have worked in my case.....500 feet above the canyon floor would not have and in all likelihood would. have set me up for disaster.
Gordy can provide some excellent discussion about this kind of accident as he survived one of them!