In order to visually evaluate the shells that hit the Wadden Sea off Cuxhaven from the Altenwalde firing range, observation posts were built on the coast of Sahlenburg and on the island of Neuwerk during the First World War. The four measuring posts with the names Aegir, Berta, Caesar and Dora were probably built on the western edge of the Wernerwald in 1917. Open wooden towers had already been set up on Neuwerk before the First World War to determine the points of impact. In the mid-1920s, these wooden frames were replaced by solid measuring posts made of Hamburg clinker bricks. During the firing tests between 1937 and 1945, these towers remained in active operation on the Wernerwald and on Neuwerk. They were also used for optical airspace surveillance.

Today, just a few kilometers in the mudflats off Sahlenburg, the ammunition restricted area is still marked by warning signs. Many test shots were fired from the Altenwalde firing base at medium distances in this area and recorded using the observation towers. Until the 1990s, employees of the bomb disposal service were busy during low tide phases recovering washed-out ammunition remnants or rendering them harmless by blasting them on site. Even today, explosive devices uncovered by nature are still being discovered at irregular intervals and have to be rendered harmless by the bomb disposal team from Hamburg or Lower Saxony. However, this has occasionally happened in other areas of the Cuxhaven mudflats due to cross-shots or shelling of other properties.