Distance Between Two
    Points
 Pacing
 Chaining
 Temperature
 Standardisation
 Catenary
 Slope
 Tension
 Tachaeometry
 Stadia System
 Measurement of
    Tacheometric Constants
 Refraction and Curvature
 Theodolite
    Tachaeometry
 Field Tachaeometry
 Electronic Tachaeometry

One of the fundamentals of surveying is the need to measure distance. Distances are not necessarily linear, especially if they occur on the spherical earth. In this subject we will deal with distances in Euclidean space, which we can consider a straight line from one point or feature to another.

Needless to say many varied methods have been developed over the millenia to measure distances, and depending on the desired quality of the result, many of these are still current today. The table below gives a brief summary of relevant techniques and their respective accuracies.

Method	Relative Accuracy	Use
Pacing	1:100	Rough identification surveys
Chainage	1:10,000	Title & Engineering surveys, Control
Range Finder	1:300	Navigation, Artillery ranging
Tachaeometry	1:1000 1:5000	Site Investigation, Mapping, Plans
Electronic Distance Measurement (EDM)	1:10,000 1:100,000	Title & Engineering surveys, Control, Geodetic surveys, Deformation monitoring

Apart from guessing and pacing, all methods need a tool or instrument of some kind, and the higher the order of accuracy the more sophisticated (and expensive) the instrument.

Use the next button to find out about some of the instruments and their usage: