surveying one liner important notes for objective | surveying important notes | surveying notes

SURVEYING-

 Theory of probability applied to accidental

error only.

 The difference between the most probable

value and its observed value is residual error.

 Geodetic surveying is different from plane

surveying because of the curvature of the

earth.

 The error due to bad ranging is cumulative

positive.

 Offsets are short measurements from chain

line.

 Invar tape is generally used for short

measurements.

 An invar tape is made of an alloy of nickel and

steel.

 Number of links in a 30m chain are 150.

 Ranging is the process of aligning the chain in a

straight line between two extremities.

 The principle of ‘working from whole to part’

is used in surveying because of accumulation of

errors is prevented.

 A metallic tape is made of cloth and wires.

 For a well conditioned triangle no angle should

not be less than 30’ and not more than 120’.

 The position of a point can be fixed more

accurately by perpendicular offsets.

 The main object of check line is check the

accuracy of the work and the main object of tie

line is to take the details near by the objects.

 River is an obstacle to chaining but not ranging.

 A building is obstacle to both ranging and

chaining.

 The angle of intersection of the two plane

mirrors of an optical square is 45’.

 45’ angle is used to setup using French cross

staff and any angle is set up using adjustable

cross staff.

 Method of perpendicular offsets involves less

measurements on the ground.

 The correction for sag is always subtractive.

 Cross staff is an instrument used for setting out

right angles.

 Line ranger is not used in measuring the

perpendicular offsets.

 If the length of the chain is found to be short on

testing it can be adjusted by straightening the

links.

 The maximum tolerance in a 20m chain is

5mm.

 For accurate work steel band is used because

it is practically inextensible and is not liable to

kinks when in use.

 The length of the chain is measured from

outside of one handle to outside of another

handle.

 Prismatic compass used for WCB and

surveyor compass used for QB.

 For a line AB the fore bearing of line AB and

back bearing of AB exactly differ by 180’.

 Local attraction in compass surveying may

exist due to presence of magnetic substance

near the instrument.

 Declination-the horizontal angle between the

true meridian and magnetic meridian.

 Azimuth-the angle between the true meridian

and a line.

 Dip-horizontal angle with respect to inclination

of dip of the needle.

 Agate cap is fitted with a prismatic compass.

 Theodolite is an instrument used for measuring

the both horizontal and vertical angles.

 Size of the theodolite is specified by the

diameter of lower plate.

 Spire test is used for adjustment of horizontal

axis.

 A level line is a line parallel to the mean

spheroid surface of the earth.

 On turning point both back sight and fore

sights taken.

 In rise and fall method of levelling provides

complete check on BS FS and IS.

 Height of the instrument method is less tedious

and quicker.

 The sensitivity of a bubble tube can be

increased by increasing the diameter of the tube.

 While doing the levelling in undulating terrain

it is preferably set the level on one side of the

slope.

 Dumpy level is suitable when many readings

taken from single station.

 A series of closely spaced contours called steep

slope.

 Direct method of contouring is more accurate.

 Tachometric method is most suitable for hilly

terrain.

 Hillock-higher values inside lower values are

outside.

 Valley-higher values are outside and lower

values are inside.

 Contour interval-the vertical distance between

the two consecutive contours.

 Benchmark is established by spirit levelling.

 Plane table surveying require least office work.

 Detailed plotting is generally done by radiation.

 The size of plane table is 600mm*750mm.

 Plumbing fork is used for accurate centring in

plane table survey.

 Intersection method is used for locate the

position of inaccessible points.

 The two point and three point problem are the

methods of orientation and resection.

 Bowditch rule is used when both angular and

linear measurements are equal.

 Transit rule is used when angular

measurements are more precise than linear

measurements.

 Deflection angle-the angle between the

prolongation of preceding line and the forward

line.

 Substance bar used for measurement of

horizontal distance in undulated areas.

 Over turning of a vehicle can be avoided by

providing transition curves.

 Different grades are joined together by vertical

curve.

 The shape of the vertical curve generally

provided is parabolic.

 Agonic line is the line joining the points of zero

declination.

 Altimeter-height measuring, fathometer-depth

measuring, passometer-distance measuring.

 Clino meter-angle measuring, pantograph-plan

enlarging or reducing, tellurometer-microwave

instrument.

 Offsets are lateral measurements made with

respect to the main survey line.

 To determine the length of the bridge

triangulation is used.

 Heliograph is a type of sun signal is used in

triangulation work.

 Topographical surveying-to determine the

natural features of the country.

 Cadastral surveying-to determine the

boundaries of field.

 City survey-to determine the railway, drainage,

road features of the country.

 The fix of a plane table from three known

points is good if the middle station is nearest.

 Plane alidade is used to measure the horizontal

and vertical distances directly.