My scout leader always taught me "never navigate by woods". The reason? It doesn't take long to chop down a forest and invalidate your assumptions.
I remember taking part in 2-day team orienteering competition. We had walked very accurately on a bearing to where the checkpoint should be, but it wasn't there. My friend had taken the bearing on the corner of a wooded area. Looking more closely at the wooded area, we could see a large area of tree stumps next to it...
(We reorientated ourselves, found the checkpoint, and came second in the competition.)