Surveying and Levelling Instruments, Theoretically and Practically Described. For construction, qualities, selection, preservation, adjustments, and uses; with other apparatus and appliances used by civil engineers and surveyors in the field.

CHAPTER XII.

Chapter 1241 wordsPublic domain

INSTRUMENTS TO MEASURE SUBTENSE OR TANGENTIAL ANGLES TO ASCERTAIN DISTANCES:--Historical Notes of the Method--Principles Involved-- Stadia Measurements, Direct and by the Ordinary Telescope-- Corrections for Refraction of the Object Glass--Stanley's Subtense Diaphragm--Anallatic Telescope of Porro--Tacheometers--Stadia-- Omnimeter--Field book--Bakewell's Subtense Arrangement 355