Abstract: The invention relates to a face shield comprising a lens. In order for the shield to have versatile properties and a simple structure and to utilize various apparatuses provided with a display, the shield comprises holding means for detachably receiving a wrist watch-shaped apparatus including a display, and optical apparatuses for displaying information provided by the display in a lens area. The shield is then preferably a diver's mask and the apparatus is a dive computer. The holding means preferably comprise a frame portion and instant attachment means.

Abstract: A navigation system and method for diving operation in view of facilitating navigation under water to a specific location, in particular navigation back to a dive starting point, i.e., to the place from which the diving was started. The system includes a base station fixed to the starting point, such as a boat or equivalent, and arranged to transmit a signal to its environment, and a mobile unit carried along by the diver. The mobile unit includes a compass and a locating part which receives the signal transmitted by the base station. The locating part converts the signal to information on the return direction, and combines the information on the return direction with the magnetic information on the direction obtained from the compass, so that the information on the return direction from the position of the diver when the signal is received is maintained irrespective of the momentary location and position of the diver and the mobile unit.

Abstract: An arrangement for correcting declination in an optically readable bearing compass having a body enclosing a hermetically sealed capsule containing a compass card and a main reading line calibrated indicate bearing to the earth's magnetic pole without correction of declination. The compass body further includes an opening or passage having an optical system therein suited to facilitate taking the bearing indicated by the wind rose. The compass has a movable auxiliary reading line which is adjustable with respect to the compass body and the main reading line to both sides from its center position corresponding to the zero value of declination thus permitting the correction of bearing error caused by the geographic displacement between the true North Pole and the magnetic north pole.