Geodetic measuring is undertaken in order to map the movements in Vasa’s hull. We have chosen this particular geodetic measuring system as it is extremely accurate, showing movements of less than I mm. Measurements have been made twice a year in the spring and autumn since the year 2000, and takes two people about two weeks to do. We measure 350 points on the outside of the hull and 50 on the inside. The system was constructed in collaboration with the Royal Institute of Technology, on behalf of the museum.

Every measurement begins with positioning the measuring instrument, a total station, in our coordinate system via a number of prisms which are mounted on the walls of the museum. We make the presumption that the building stable. Each point on the hull is then measured from at least two different sets of points and then twice more from every succeeding point. This increases the accuracy and minimizes the risk of faulty readings.

After each measuring session, the data is worked through and compared with previous results. We are then able to see how the 400 points move over time. We can say with certainty that Vasa is settling downwards ca 1 mm per year, with some more localized deformations/movements. Although this is not a problem in the short term, Vasa’s preservation unit is working to develop a new support system as well as improving Vasa’s current structural stability.

Geodesy (from Latin geo = Earth and desi = part: meaning fixing a point’s position in a coordinate system).