Run straight ahead and on to the elevated plateau like geographical landmark in front of you. Take out the guard patrolling the plateau. You may try to sneak past him by hiding behind the trees, but that will make you a target of the snipers positioned at the tower that commands a good view of the plateau. By taking the guard's clothes, you can disguise yourself and avoid becoming a sniper target. The mission requires that you do not be questioned by any guard, since being questioned and asked for an ID will most certainly blow 47's cover.