Wye and Dumpy levels were discussed in Article 17. Both of these used a level bubble to determine a horizontal plane. The first real innovation following the use of the level bubble occurred in Europe around the 1950s with the development of the automatic level. Automatic levels use compensating devices, for example a pendulum apparatus, in place of the bubble.
The first automatic level that was used extensively was the Zeiss Model Ni2. It was introduced in 1950. By 1970, Zeiss stated that the company had produced over 50,000 levels of this sort in the past twenty years. Other companies followed. The collection has several automatic levels; a Zeiss Ni2, a Topcon AT-G6, a Kern GKO-A and a Jena Ni025.
Level, Sokkisha, TTL5
Level, Tokyo, Model T2
Level, Topcon
Level, Zeiss
Level, Wild, N2
Level, Kern, GKO-A