News - Week 5: 1159 points of History

Fig 1. Mette behind the total-station – a task that requires patience and precision

Fig. 2 Niels surveying underwater - here he is ‘drawing’ the section of U:1

Fig. 3 Eva aligns the prism pole – a hard task that requires steady hands

Author: Mette Arenfeldt, Eva Mortensen and Niels Bargfeldt

When surveying under water more people are needed than when it is done on land. On Land one person can do the job using reflector less laser, but for surveying submerged structures at least three people are required.

The surveyor behind the Total Station (Fig. 1), when not being able to see the actual structures, is shooting with infrared, which reflects on a prism. The diver, who decides what points to shoot, is literally the one who ‘draws’ the structures (Fig. 2). However the diver cannot both choose the points and level the prism, which is where the third person comes into the picture. Depending on the depth of the water, this can be either another diver or a person from land in a dry suit but without a mask (Fig. 3).

All three tasks are demanding. It can be extremely hot to stand in the sun, especially for the prism holder wearing a dry suit. The diver, on the other hand, can get cold even in the beginning of October, because he or she is lying almost completely still in the water. In order to be efficient the team has to work in unison, so that the diver times his or her breathing to the movement of the prism holder and the pace of the surveyor shooting the points from land.

This year we have a dedicated survey team, with a surveyor in the water and one behind the Total Station at all times. That way, important finds, whole structures as well as trench outlines and sections can be surveyed as necessary. This makes the survey work very efficient and sometimes we exceed our own expectations!

Monday was just such a day: we shot 1159 points – a seasonal record! We have now completed the documentation of structure U:1 in Area 2 and started surveying a shipshed in area 3. New interesting blocks that have been come to light in the trenches have also been mapped, and each day we get a clearer picture of what is going on under the surface of the muddy waters of Zea.