Building established in 1773 for military purposes. NGO since 1880.

A good place to introduce the post-glacial uplift.

Maximum relative sea level at 221 masl today (a bit above the level of Sognsvann).

Uplift since the Viking age: ca 3,8 meter.

Normalhøydepunktet was moved to Mandal in 1954 (where the elevation system “normalnull 1954” is based). Normalnull is the mean sea level.

Data from Mangerud et al., 2018:
Present-day uplift
Measuring subsidence in Oslo (INSAR: Radar from satellites;
Laser-based digital terrain models.
Holocene deposits. From
Borehole database (water and energy), many with some geological info, like depth to basement.