The DHI in the years 1976 and 1977 
139 
iron ships, indication errors of gyro-compass installations caused by course 
manoeuvres, and the efficiency of optically reflecting substances and radio aids 
for search and rescue in cases of distress at sea. In order that alerting, search 
and rescue in cases of distress at sea can be incorporated into the future marine 
radio satellite system INMARSAT, the DHI is intensively working in the 
responsible international authoritative bodies.