TACHEOMETRIC SURVEYING - Civil Engineering Notes KPSC

TACHEOMETRIC SURVEYING 


• Tachometry is a branch of angular surveying in which the horizontal and vertical distances ofpoints are obtained by instrumental observations. 
• Chaining is entirely eliminated in tachometry. 
• This method is most rapid but less accurate. 
• The accuracy of tachometry is less than that of chaining 
• The primary object of tacheometry is the preparation of contoured map or plan. 
• The instruments used in tacheometry are a tacheometer and a leveling or stadia rod. 
• Tacheometer is a transit theodolite having a stadia telescope ie, a telescope fitted with two additional cross hairs called stadia hairs.
• Stadia rod is 5 cm to I5 cm wide and 3 to 4m long. It is graduated in meters, decimeters and centimeters. • For short sights up to 100m a stadia theodolite and a leveling staff may be used. But for long sights, say more than 300m a tacheometer and stadia rod are required. 

TACHEOMETRIC METHOD 

I. STADIA METHODS 

1. Fixed hair method: 
• This is the most commonly used method in tachecmetry, In this method the stadia hair interval is fixed and the staff intercept IS taken. 
• The required horizontal and vertical distances are computed from this staff intercept. 
• In case of inclined sights, the staff may be held vertically or normal to the line of sight 

2. Movable hair method : 
• This method is rarely used. 
• In this method, the stadia wires can be moved by means of micrometer screws. 
• The staff is provided with two targets fixed at a known distance apart, usually 3m. 
• The variable stadia interval is measured. The required distance may be computed from this value 

II. TANGENTIAL METHOD 
• This method is used when the telescope of the instrument is not equipped with a stadia diaphragm. 
• In this method a staff fitted with two targets or vanes at a fixed distance apart, usually 3m is held at the station. 
• Vertical angles to the two vanes are observed with a theodolite. 
• Calculation of distance in stadia method


PREVIOUS YEAR QUESTION PAPERS 





Comments

Popular posts from this blog

UNITS OF MEASUREMENTS, PAINTING COEFFICIENT, OUT TURN, QUANTITY CALCULATION

BASICS, SOURCES OF WATER, WATER DEMAND

MACHINE TOOLS - SHAPER MACHINE