Circa 1700 Playing Card Showing a Theodolite

Theodolites (1500 to 1800)

Theodolites have been around for more than 500 years, and are likely the most important surveying instrument ever invented. Most American collectors picture a circa 1840s British Theodolite, with its distinctive extra long telescope, when they hear the word "Theodolite". But Theodolites had been around for about 300 years before that 1840s Theodolite was made. And here is what they looked like during that 300 year run….

The Four Types Theodolites - The Astorlabe and Three Generations of Theodolites

Astrolabe (Circa 1200 to 1800)

Although the Astrolabe was designed to study the heavens, the backside of an Astrolabe could be used to measure horizontal and vertical angles.

First Generation Theodolite (Circa 1550 to 1600)

First Generation Theodolites measured horizontal angles with an alidade that rotated over an outer 360 degree scale, which was generally divided by single degrees. Based on the backplate of an Astrolabe

Second Generation Theodolite (Circa 1600 to 1750)

Theodolites evolved into much more usable surveying instruments around 1600 or so. Makers started producing larger diameter instruments that featured cutouts inside the circle to reduce the weight of the instruments.

Third Generation Theodolite (Post 1725)

The Third Generation - Altazimuth Theodolite was born in 1725 when an instrument maker put a telescope on top of a Second Generation Theodolite.