Altimeter

The altimeter was used by the Bulgarian fortress siege artillery to measure the height of the shrapnel explosion during shooting exercises, to obtain accurate data for processing the results of the actions. For this purpose, it was placed in the training observation post near the target.

This altimeter consisted of a rectangular wooden or cardboard frame A with dimensions of 10x30 cm, on which horizontal threads of ½ cm were stretched in front. In front of the frame, a horizontal cord Б Б, fixed to two supports, was placed a few meters away. The device was set so that one of the central threads (i.e. zero) and the cord were on the same line pointing to the target. As soon as the spread of shrapnel was noticed, the observer turned his eye to the line connecting the spread with the cord, observing between which threads the spread originated and from this he determined its height, the value of 1 division (between two threads) being determined in advance. Therefore, at a distance of 5 m from the wire to the frame, each division had a value of 1/1000 of the distance.

SOURCE :

Ръководство за занятията въкреспостата артилерия. Част IV. Подготовка и служба на наблюдателите, Sofia 1902, pp. 41-43.