Progress in opto-electronic components combined with the development of the micro-processor made it possible to realize a new family of surveying instruments which can measure angles and distances, combine these readings and yield true three dimensional position information. The paper describes the HP3820A which combines a one arc second tiltmeter and a microprocessor in a single instrument.
Alfred F. Gort,
"Fully Integrated Microprocessor-Controlled Surveying Instrument", Proc. SPIE 0230, Minicomputers and Microprocessors in Optical Systems, (8 August 1980); doi: 10.1117/12.958821; https://doi.org/10.1117/12.958821