Linear Measurements

Methods of linear measurements

1) Direct Method

• In the direct methods, the distance is measured during fieldwork wing chain on a tape.

2) Optical Methods

• In the optical methods, principles of the optic are used. The distance is not measured in the field but it is computed indirectly.

• The instrument used for making observations is called a tachometer.

3) E.D.M Methods

• Electromagnetic distance measuring (EDM) instruments have been developed quite recently. This is practically replacing the measurement of distance using chains or tapes.

Approximate methods

• It could be better to have some idea of approximate methods of measuring the distances.

• The methods given below may be used in reconnaissance or for detecting major mistakes in linear measurements obtained with a chain on tape.

1) Pacing

• A distance between two points can approximately be determined by counting the number of paces and multiplying it by the average length of the pace.

2) Passometer

• It is a small instrument that counts the number of paces.

3) Pedometer

• This instrument directly gives the distance by multiplying the number of paces with the average pace length of the person carrying the instrument.

4) Speedometer

• This is used in automobiles for measuring distances.

5) Odometer

• An odometer is a simple device that can be attached to the wheel of bicycles or any such vehicle.

• The odometer registers the number of revolutions made by the wheel.

• The distance covered is equal to the product of the number of revolutions and the perimeter of the wheel.

Instrument used in chain Surveying

The following instruments the used while chaining.

• Chains
• Tapes
• Arrows
• Ranging rods and offset rods
• Pegs
• Plumb-bob etc.