A roll of less than half of the target number results in a Critical Hit. This results in the following:
A character with Survival skill can possibly identify and avoid the encounter. Compare the margin of success. Each 2 points of success can offset 1 point of success on the Encounter roll. If Survival roll is made by more than the encounter roll, the encounter can be avoided. If the Survival roll is made, but not by more than the Encounter roll, the encounter occurs at normal sighting distance, but with the party not being surprised. If the Survival roll fails, the encounter occurs at a distance defined by the encountered creature's perception.
A character 33+ meters (i.e. -4 range modifier) can avoid any group penalties to the Survival roll. The group penalties are the same for Hunting with groups in HERO System Skill. A second character with Survival can use their skill to offset the group penalty.
Generally 3 times: morning, late afternoon, night