Data from geotechnical drilling along the Cityringen alignment were used to calculate how much earth pressure tunnels, stations and shafts could withstand. In addition, trial pumpings from the water-bearing layers in the subsoil have shown where the water-bearing layers are located and how deep into the subsoil the effect of the construction work can be traced. This has helped prevent damage to buildings in the area.
Particularly vulnerable structures are measured and photographically registered in order to precisely determine whether construction work will affect the structures around it. The excavation of so-called injection wells, subterranean pockets filled with a stable material, helps ensure that the drilling of the tunnels affects the surrounding terrain as little as possible.
The final stage in the preliminary survey work were archaeological excavation. At a number of sites, particularly at the city core, archaeologists from the Museum of Copenhagen were following the first phase of construction (see below) in search of prehistoric finds and cultural artefacts that could teach us more about the history of Copenhagen.