An altitude reporter comprising an altimeter, electrooptical means for tracking the position of the indicator of the altimeter first means including a register for registering the position of the indicator and providing pulse group series output corresponding to such a position, and second means for operatively connecting the first means to the electrooptical tracking means. This second means is effective, when the indicator moves in one direction, to operate the register to add increments of such movement and, when the indicator moves in the opposite direction, to operate the register to subtract like increments of movement. The tracking means is arranged so that it will, in no way, interfere with the free movement of the indicator of the altimeter. The system of the present invention, therefore, comprises a standard aircraft altimeter and means for reading the altimeter, which reading means is arranged so that it will, in no way, disturb or change the characteristics of the altimeter.
