If you're flying in Europe - get a copy of New Pans OPS.
TERPS, if flying in the States.
As for "established", I'd say you're well within limits if inside +/- 2.5NM of the published arc. The primary obstacle clearance area includes a 2.5NM sector on either side of the arc, where the obstacle clearance is minimum 300m. From there on, the obstacle clearance decreases linearly to zero, when reaching 5nm either side of the arc. According to NPO.