Direct Ranging
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Ranging is used to locate intermediate points along a survey line that is longer than a chain length. There are two methods of ranging: direct ranging and reciprocal ranging. Direct ranging involves fixing ranging rods at the starting and ending points (A and B) and using signals from the surveyor to guide an assistant holding a third rod to align it along the survey line at an intermediate point (C). Once aligned, the chain is used to measure the distance from the starting point to the intermediate point.
Direct Ranging
- 1. RANGING
- 2. Ranging • When a survey line is longer than a chain length, it is necessary to align intermediate points on chain line so that the measurements are along the line. • The process of locating intermediate points on survey line is known as ranging. • There are two methods of ranging viz., direct ranging and reciprocal ranging.
- 3. Ranging
- 4. Direct Ranging • If the first and last points are intervisible this method is possible. • Stations A and B in which an intermediate point C is to be located. Point C is selected at a distance slightly less than a chain length. At points A and B ranging rods are fixed. The assistant holds another ranging rod near C. Surveyor positions himself approximately 2 m behind station A and looking along line AB directs the assistant to move at right angles to the line AB till he aligns the ranging rod along AB. Then surveyor instructs the assistant to mark that point and stretch the chain along AC.
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- 13. Ranging ( Code of Signals) Sr. No. Signal by the Surveyor Meaning of the signal to the assistant 1 Rapid Sweep with right hand Move considerable towards left 2 Slow Sweep with right hand Move slowly towards left 3 Right arm extended Continuously move towards left 4 Right arm up and move to the right Plumb the rod towards left 5 Rapid Sweep with left hand Move considerable towards right 6 Slow Sweep with left hand Move slowly towards right 7 Left arm extended Continuously move towards right 8 Left arm up and move to the right Plumb the rod towards right 9 Both hand above head and brought down Ranging is correct 10 Both arm extended horizontally and brought down quickly Fix the ranging rod