Chirp profile in shallow water along the shore of the harbour of the Viking Age settlement of Haithabu. The yellow arrows mark the main concentrations of poles representing the landing piers running approximately perpendicular to the profile. The features observed in the seismic profiles have been verified as linear concentrations of poles. The surface of the sea floor is marked by the broken yellow line. The depths to the right are measured from the bottom of the fish. The actual depths are, in this case, approximately 20 cm greater. Recorded by Grøn & Hoffmann in 1996.