Question

Consider the following errors associated with EDM:

1) Precise centering at the master and slave station.

2) Error due to variation in meteorological conditions like temperature, pressure, humidity.

3) Errors associated with pointing/sighting of a reflector.

Which of the aforementioned errors can be classified as atmospheric errors?

1. Only 1 and 2
2. Only 2
3. Only 1 and 3
4. Only 3

Answer 1

Correct Answer - Option 2 : Only 2

Concept:

Electronic distance measuring(EDM) instrument:

• It is a surveying instrument for measuring distance electronically between two points through electromagnetic waves.
• Electronic distance measurement (EDM) is a method of determining the length between two points, using phase changes, that occur as electromagnetic energy waves travel from one end of the line to the other end.

Errors in Electronic Distance Measurement Instruments are as follows:

Error in EDM	Details
Personal Errors	Inaccuracy in initial setups of EDMs and the reflectors over the preferred stations
	Instrument and reflector measurements going wrong
	Atmospheric pressures and temperature determination errors
Instrumental Errors	Calibration errors
	Chances of getting maladjusted time to time generating frequent errors
	Errors are shown by the reflectors
Natural Errors	Atmospheric variations in temperature, pressure as well as humidity. Microwave EDM instruments are more susceptible to these.
	Multiple refractions of the signals.

Hence, errors due to variations in meteorological conditions like temperature, pressure, humidity, classified as atmospheric errors in EDM.