Reveal Approach (sage ability)
A character with heightened senses cannot be approached through the use of stealth to a distance less than the character's present experience level. Thus, a 7th level possessor of this ability could not be approached nearer than 7 hexes, before the character would be made aware of the approach.
However, note that the ability in no way preserves the character from being surprised, nor does it have any influence on the character's initiative once the approacher is detected. These things are resolved as in any other stealth-approach situation.
See Heightened Senses