The CAPELLA is the first larger survey ship built by Fassmer Shipyard for German Federal Marine and Hydrographic Authority (BSH) responsible for hydrographic survey activities and searching for shipwrecks, as well as for publishing of sea charts, nautical publications and the distribution of nautical warnings and announcements.
The main task of the CAPELLA is hydrographic surveying in shallow waters off the coast, and in particular the coastal bays in Mecklenburg-Vorpommern and the mud flats in Schleswig-Holstein and Niedersachsen. For the surveying tasks, apart from the mother ship with a draught of only 1.6 m, there are also two survey boats and a working rubber dinghy. All four units have similar surveying equipment, consisting primarily of top quality surveying depth sounders and surveying GPS receivers. Both convert the measurement of the water depth and that of the corresponding position into a depth profile registered with decimetre accuracy continuously while the ship is moving. These profiles are extended to “profile mattresses”, a sequence of parallel tracks, and are thus used to portray the surface of the sea bed, primarily for making up sea charts.
The rubber dinghy with its jet drive can be used for surveying right up to the beach, i.e. up to water depths of approx. 50 cm. It is manned by a driver, a surveyor, a depth sounder and a DGPS system with a laptop and display for the driver.
The survey boats which work in the coastal areas at water depths from 1 m have more sophisticated equipment. The depth sounders work in two frequency ranges, the GPS position of the satellites is corrected using a differential procedure, and the boat 2 has a side scan sonar system. It is an acoustic ground measuring system taking pictures of the sea bed in near-photo quality. On the CAPELLA itself, surveying is carried out on a special panel on the bridge, using the same principle. The system also registers the ship movements and swell speed data, as well as the water levels at the water gauges around the German coast (this latter function by radio). Together with all these data, the sounding data from all four units undergo post-processing using complex software for filtering and error processing in the surveying office. The cleaned data are then processed into topographic charts of the sea bed, creating the basis for the actual sea charts later on.
Moving along the tracks and exact steering to the positions requires a navigation system which complies with the high surveying demands. A gyro-compass system, supplemented by a magnetic compass system which can feed the repeater compasses in an emergency, is responsible for the precise registration of the ship direction. The ship speed is registered with an electromagnetic log and a sat log. The rudder is controlled manually or by the autopilot. The radar system supplies images of the surroundings which are supplemented by an electronic sea chart. The gathered meteorological data are displayed on a PC monitor.
For internal communications (intercom, public address and paging system, telephone and signaling system running without batteries) and for external communications (GMDSS through to satellite communication systems, standard C), the ship is equipped with various systems going over and beyond the stipulated requirements. The survey boats and the rubber dinghy are included in the communications concept.
Source: www.fassmer.de