MINOR INSTRUMENTS - Civil Engineering short notes

MINOR INSTRUMENTS

 1. HAND LEVEL
• A hand level is a small leveling instrument which is held in hand while levelling. 
• It is used for approximate determination of elevations in 
• reconnaissance, 
• preliminary surveying, 
• locating contours on the ground 
• for taking short cross-sections in profile 

2. ABNEY LEVEL
• Modified hand level 
• Can be used as a hand level for levelling and as a clinometer for slopes 
• Vertical scale is extended type 

3. CLINOMETER
• Aka tangent clinometer 
• Used to measure elevation of two points by measuring inclination of line of sight 
• Used for plane tabling 

4. CEYLON GHAT TRACER 
• Used for measuring slopes 
• It is specifically used to set out grade contour in preliminary survey of road in hills 

5. SEXTANT 
• A sextant is an instrument used for measurement of the horizontal and vertical angles.
• Arrangement of 2 mirrors helps observer to sight 2 objects simultaneously 
• Works on principle of double reflection 
• Has graduated marks from 0 - 120*, subtending an angle of 60 @ center 

6. BOX SEXTANT 
• Pocket instrument used for measuring angles 
• Can be used as an optical square to set out 90* 
• Used to locate inaccessible points in chain survey by intersection 
• Used for locating details by radiation mtd in traversing 
• It can be used in moving boat or a ship Ceylon ghat tracer sextant Box sextant 

7. MINING DIAL 
• Simple theodolite fixed with a compass 
• Used in mine surveying 

8. PLANIMETRE 
• Used to measure the area of irregular figures 
• Mechanically measure area of plan to map 

9. PENTAGRAPH 
• Used for enlarging or reducing plan 

10. FATHOMETER 
• Used for measurements at depth of water bodies 

11. HELIOGRAPH 
• Used as a sun signal in triangulation survey 


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