Linear Measurements in the Surveying by Direct Method
The Linear measurements in surveying can be performed by mainly 3 methods namely direct method, electromagnetic methods & optical methods. The direct method is the common method that employs the chain, tape or any other instrument to measure the linear distance.
Various methods coming under the direct method of the linear measurement are.
- Odometer and speedometer
1 – Pacing
The pacing technique is mostly employed in the preliminary surveys & explorations. In this method the Land Surveyor is required to conduct the rough survey quickly. This also roughly check the distance measured by the other means.
In this method the number of the paces between the 2 points of the line is counted. Knowing the average length of pace helps to know the length of line. The length of pace is dependent on the person who is measuring the ground the speed of the pacing & the slope of the country.
By walking on an approximate level ground over various lines of known lengths helps to the determine the length of one’s natural step. Performing pacing over rough ground or on slopes is the difficult process.
2 – Passometer
The Passometer is a watch like instrument that is the carried on the person’s pocket or tied on the man’s leg. This instrument records paces when the man moves from 1 point to another.
This technique hence overcomes the monotony & strain in counting the paces by the Land Surveyor. The distance is the calculated as the product of the number of the paces & the average length of the pace.
3 – Pedometer
Pedometer is the similar device like Passometer that automatically measures the distance. A pedometer is the best in measuring the vertical distances.
4 – Odometer
Odometer is an instrument that measures the number of the revolutions of a wheel. The number of the revolutions taken to cover the length multiplied by the circumference of the wheel gives value of the distance covered.
This instrument does not provide the accurate results on an undulating surface. When the surface is smooth and the speedometer used in the vehicles can be used.
5 – Chaining
Chaining method determines the distance by means of the tape or a chain. This is 1 of the accurate methods to determine the linear measurements. The chain is used for the ordinary precision. Tape or the special bar is used to measure distance with high precision.