Published on 4 July 2025

Technical boundary in the Lake Constance

For the largest part of Lake Constance, there are no legally defined borders. Within the framework of the Lake Constance Conference, the surveying authorities of the neighbouring countries resolve technical issues relating to Lake Constance in a pragmatic and cooperative manner.

Romanshorn harbour at dusk, with a ferry heading for Germany in the background.

Did you know that there are no legally valid international boundaries for the largest part of Lake Constance - the so-called Obersee (Upper Lake)? Switzerland is assuming a real sharing in the middle of the lake. Germany and Austria regard the Obersee as a condominium in the joint control of the neighbouring countries. Therefore, common professional tasks ‘around Lake Constance’ must be solved pragmatically and in partnership.By defining a ‘technical boundary’, the geodata of the surveying authorities can now also be made available in harmonised form for the Obersee region.

The Lake Constance Conference of Surveying Administrations

Federal Office of Topography swisstopo

Department Communication and Web
Seftigenstrasse 264
3084 Wabern