Surveyor's have always needed the ability to perform mathematical computations.  Prior to the introduction of electric calculating machines, there were many devices used by surveyors to speed their work with various efforts to increase accuracy.  The following display shows several examples of these calculating devices used during the late 1800's thru 1960's prior to the advent of modern digital devices.

Brunsviga "Midget" Calculator

Add, subtract, multiply, divide and square root.  Allows 9 digit by 10 digit calculations.  Patented in 1906.

Thacher's Calculating Instrument

Equivalent of a 360" long slide rule, allows calculations to a precision of 1:10,000.  Patented in 1881.

Fowler's "Magnum" Calculator 

A multi-scale circular slide rule.  Early to mid 1900's.

The Fuller Calculator

Equivalent of a 500" long slide rule.  Allows calculations to a precision of 1:10,000.   Early to mid 1900's. 

Otis King's Patent Calculator

Equivalent of a 60" long slide rule

Curta Calculator

Add, subtract, multiply, divide and square root.  Allows 6 digit by 8 digit calculations.  The "field crew" calculator of the 1950's and 60's.

Traditional 6" and 12" Slide Rules