Martin Edström is coordinating his team from the campsite inside the second doline, or sinkhole, in Hang Son Doong. Talking over the radio, he can monitor the team’s progress as they spread out with lights and equipment inside the cave. On top of the hill behind him, inside the doline jungle, assistant photographer Erik Hinnerdal is rigging the camera for a 360 degree image soon to be captured during the #SonDoong360 expedition.