Sam Millard
WKR
[video=youtube;sTRV_MVHzlA]https://www.youtube.com/watch?v=sTRV_MVHzlA[/video]
Good stuff, two drawbacks - you have to know how to draw and have to have enough time to bother. I would argue that spare batteries/kestrel, printed range card and having a mechanical inckinometer would do the trick. My single point of failure is my range finder, but I could always bring a spare
Using range cards will teach you to look at a hillside a little differently. With some experience and attention to detail, a shot can be taken with only the information you've placed on the card.