Drop down off the roof onto the flat ledge with the Endurance Overlook Day Camp. Lying on the ground near the campfire is a document (2/4), a page from Alex's journal, part of the Endurance Crew set.
There are 2 edible plants nearby. If you face the old truck, one plant is on the left, the other is on the right.
Beyond the plant on the left, in the tunnel behind the truck, there's a relic (2/3), a Japanese 2 Sen Coin. Examine the back of it for more info and XP.
Beyond the second edible plant, between the stacked crates and the cliff's edge, is a GPS cache (4/5).