At time of sighting instrument towards target, first step involves rotation of instrument?s optical axis from instrument north in horizontal plane.

The frequency range of microwave instrument is about 3-30 kHz which provides it ability to cover a range up to 100km. The usage of gamma rays is not possible in case of Total station.

Micro processor provided in instrument helps in saving data and helps in transferring it to system, by which it can be viewed in different software.

In total station, distance between two point scan be determined by measuring phase difference between transmitted and reflected signals. Phase difference can be expressed in terms of fraction of cycles, which provides best output for quick calculation and for easy understanding.

A total station is a combination of an electronic odolite and an Electronic Distance Measurement. This combination makes it possible to determine coordinates of a reflector by aligning instruments cross-hairs on reflector and simultaneously measuring vertical, horizontal angles and slope distances.

In high frequency zones, phase comparison techniques cannot be applied. The high frequency may be determined as 5*10⁸ Hz which may correspond to a wave length of 0.6 m.

Infra-red instruments use infra-red waves as carrier waves. These are widely used in present day as se are able to provide information with less economy.

The elevation of ground beneath reflector can be given as
R_z = I_z + S_d * cosZ_a + I_h ? R_h. On substitution, we get
R_z = 12.76 + (3.76*cos (3?43?)) + 2.93 ? 0.987
R_z = 18.45 m.

Electronic Distance Measurement method is based on generation, propagation, reflection and subsequent reception of electromagnetic waves. The type of electromagnetic waves generated depends on many factors but mainly, on nature of electrical signal used to generate waves. It follows above-mentioned sequence without any disturbance in it.

In general, various EDM systems available do not measure transit time directly. The distance is determined by measuring phase difference between transmitted and reflected signals, which possible only when process is done without errors.