Group Terrain Negotiation 1 (Source)

Group Terrain Negotiation

Master GTN adds 60 points to all groupmate's personal Terrain Negotiation (which is how fast they can run up/down hills and crawl speed). My understanding, and please correct me if I'm wrong, of TN is that it is capped at +100 and the first 1-50 increases hill speed and the 51-100 range increases crawl speed. The only people that get their own terrain negotiation skills are Scouts (+50) and Rangers (+50). +60 Group TN makes all non scouts roughly as fast as Novice Rangers.

The main value in this skill is that it allows non-scouts (generally medical personal) to travel with your group at the same speed as the scouts. If you've been in a group without this skill you'll often see the radar showing your group stretching out in a long line with the scouts in front and the docs huffing and puffing in back. With just Mobility III (+50 group TN) you will see you entire squad stick together at the same speed. this will get you to your destination faster and reduce the chance of a rear straggler drawing aggro (the ones in the rear are most likey the worst equipped to deal with aggro).

Perhaps future uses of this skill will see more people crawling quickly in battle (being prone does make you harder to hit AND improves your accuracy to hit) and also might allow more combat people to drop Scout and Explore IV altogether and use those skills to bring more firepower to the table.