step 17, I brevetti

26 maggio 1907: Theodolite or similar insturment






The present invention has for its object a field-theodolite which although very small in bulk and easily transportable constitutes an instrument of great precision for the measi S urement of azimuthal and zenithal and bearing or direction angles relatively to the magnetic north.

https://worldwide.espacenet.com/patent/search/family/002916595/publication/US848132A?q=magnetic%20theodolite

8 novembre 1923: Improvments in compass fitted theodolites











According to the present invention the compass is united with the horizontal circle, i.e. the magnetic needle is so disposed inside this circle that, on the telescope being approximately adjusted to the magnetic meridian, the magnetic needle is also visible in the ocular field simultaneously with the horizontal circle. With a view to renderingharmless any errors of eccentricity, the theodolite may be so constructed, that two opposite places of the horizontal circle and also both ends of the magnetic needle are simultaneously visible.

https://worldwide.espacenet.com/patent/search/family/005756297/publication/GB197307A?q=magnetic%20theodolite