Telescope Focusing Process

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What is the main purpose of compass surveys?

To measure distances using a magnetic compass

To provide accurate measurements for small areas

To provide rapid filling of details in larger surveys (correct)

To align the compass needle to the earth's magnetic field

When is chain survey preferred over compass survey?

When magnetic disturbances are present

For large areas where rapid work is required

When the survey line direction is important

For small areas where high accuracy is needed (correct)

What is one major drawback of using a compass for determining the bearing of a line?

The compass needle aligns inconsistently with the magnetic field (correct)

High level of accuracy in determining direction

Inability to measure distances accurately

Constant reference point provided by the earth's magnetic field

What is the main use of a prismatic compass?

For measuring magnetic bearings Signup and view all the answers

Why should care be taken when using a compass survey?

To prevent magnetic disturbances from affecting results Signup and view all the answers

Which type of survey is mainly used for rapid filling of details in larger surveys?

Compass survey Signup and view all the answers

What is the main difference between the Prismatic Compass and the Surveyor's Compass?

The Surveyor's Compass is generally used on a stand or tripod. Signup and view all the answers

What is the purpose of the 45º reflecting prism in the Prismatic Compass?

To adjust the focus of the image of the graduations. Signup and view all the answers

What is the function of the lifting pin and lifting lever in the Prismatic Compass?

Lifting the magnetic needle out of the pivot to prevent damage. Signup and view all the answers

Which part serves as the heart of the Prismatic Compass?

Magnetic needle. Signup and view all the answers

Why do the graduations on the Prismatic Compass remain stationary with the needle?

To enable reading off the graduated arc directly. Signup and view all the answers

What is the purpose of the mirror located in front of the forward vane in the Prismatic Compass?

To provide solar observations. Signup and view all the answers

Why is the graduated circle or ring in the Prismatic Compass marked from 0º to 360º?

To measure all possible bearings of lines. Signup and view all the answers

What does the object vane in a Prismatic Compass carry?

Horse hair or black thin wire to sight object in line with eye sight. Signup and view all the answers

What is a non-magnetic metal case with a glass top in a Prismatic Compass known as?

Cylindrical metal box. Signup and view all the answers

What part of a Prismatic Compass carries a fine slit provided with an eye hole at bottom?

Eye vane. Signup and view all the answers

What is the main purpose of a surveyor's compass?

To determine the magnetic bearing of a line Signup and view all the answers

How is the bearing measured in a surveyor's compass?

Clockwise starting from North Signup and view all the answers

What is the difference between Fore Bearing (FB) and Back Bearing (BB)?

FB is taken in the direction of survey, BB is taken in the opposite direction Signup and view all the answers

If a Fore Bearing is 1200, what would be the corresponding Back Bearing?

1800 Signup and view all the answers

How is a traverse plotted after traversing with the compass?

By considering the general shape of the area Signup and view all the answers

What system measures the bearing in quadrants starting from North?

Quadrantal Bearing System (Q.B) Signup and view all the answers

What does Reduced Bearing (R.B) refer to?

Bearing converted from Whole Circle Bearing to Quadrantal bearing Signup and view all the answers

In what direction are survey lines measured in Quadrantal Bearing System?

Both clockwise and anti-clockwise Signup and view all the answers

'The bearing of a line measured with respect to magnetic meridian in clockwise direction.' Which system does this statement describe?

'Whole Circle Bearing System (W.C.B.)' Signup and view all the answers

'In this system, the bearing of survey lines are measured wrt to north line.' Which system is being referred here?

'Quadrantal Bearing System (Q.B.)' Signup and view all the answers

What is the purpose of using sun glasses in the prismatic compass?

To bisect luminous objects Signup and view all the answers

How is the centering of the prismatic compass checked?

By dropping a pebble from the underside Signup and view all the answers

What is the purpose of levelling the compass in a prismatic compass operation?

To ensure that the compass can rotate freely Signup and view all the answers

What does the term 'whole circle bearing' refer to in a prismatic compass operation?

A bearing that covers 360 degrees clockwise Signup and view all the answers

What is the reason behind variations in magnetic declination mentioned in the text?

Related to movements of the magnetic poles Signup and view all the answers

What is the secular variation related to magnetic declination?

It is a slow continuous swing with a cycle of about 400 to 500 years Signup and view all the answers

How is the magnetic bearing of a survey line defined?

The angle between magnetic meridian at starting and ending points Signup and view all the answers

What defines the direction of a magnetic meridian at any place?

The direction obtained by observing a freely supported magnetized needle Signup and view all the answers

'Angle of Declination' is defined as:

The angle between magnetic meridian and true meridian Signup and view all the answers

How does Diurnal Variation differ from Secular Variation in terms of time frame?

Diurnal Variation is a minor variation during certain periods, whereas Secular Variation has large continuous swings over centuries. Signup and view all the answers

What is local attraction in compass survey?

Influence that prevents magnetic needle from pointing to the magnetic north pole Signup and view all the answers

How is local attraction detected in a compass survey?

By observing both bearings of a line and noting the difference Signup and view all the answers

What is the first method used to eliminate local attraction?

Checking the difference of F.B. & B.B. of each line of traverse Signup and view all the answers

In a closed traverse, what is a check available for angular error?

Sum of interior angles should equal (2n-4) x right angle Signup and view all the answers

What does the transit rule apply to in surveying?

Angular measurements Signup and view all the answers

What is levelling in surveying?

Establishing height above or below a datum line Signup and view all the answers

What is a level surface in levelling?

A surface parallel to the mean spheroid of the earth Signup and view all the answers

How is horizontal surface defined in levelling?

A surface parallel to level surfaces at a specific point Signup and view all the answers

What is the role of inspection compasses in surveying?

Detecting and eliminating local attraction errors Signup and view all the answers

What is the point or surface with respect to which levels of other points or planes are calculated called?

Datum Signup and view all the answers

What is the average height of the sea of all stages of tides known as?

Mean sea level Signup and view all the answers

What is a relatively permanent point of reference with a known elevation w.r.t. a datum called?

Bench mark Signup and view all the answers

Which instrument provides a horizontal line of sight and magnifies readings far away from it?

Dumpy level Signup and view all the answers

What is the main advantage of a dumpy level over a wye level?

Solid construction Signup and view all the answers

What is a levelling staff used for?

Taking horizontal sight readings Signup and view all the answers

What imaginary line is horizontal when the bubble in the telescope is centered?

'Axis of level tube' Signup and view all the answers

What is the main purpose of differential leveling in surveying?

To determine difference in elevations of two points Signup and view all the answers

What is another term for 'Fly Leveling' as mentioned in the text?

Profile Leveling Signup and view all the answers

In surveying, what is the purpose of taking back sight readings at turning points?

To adjust the height of the instrument Signup and view all the answers

What is the method used to calculate Reduced Levels in differential leveling?

Height of Instrument method Signup and view all the answers

What does the arithmetic check ΣB.S - ΣF.S = ΣRISE - ΣFALL represent in surveying?

Verification of closure error in leveling Signup and view all the answers

Why is setting up turning points necessary in differential leveling?

To enable taking back sight and fore sight readings Signup and view all the answers

What is the term for the operation of bringing the clear image of an object into the plane of cross hairs in a telescope?

Focusing Signup and view all the answers

What is the error that occurs when the bubble is not in the center of the run in a bubble tube?

Error due to Sensitiveness Signup and view all the answers

In levelling, what is the term for the last reading taken from an instrument just before shifting it?

Fore sight Signup and view all the answers

What is the term for a point on which both fore sight and back sight are taken?

Change point Signup and view all the answers

Which type of levelling involves determining the difference in levels of two nearby points?

Simple levelling Signup and view all the answers

What is the term for carrying out levelling with respect to a temporary bench mark?

Fly levelling Signup and view all the answers

Which type of levelling involves finding reduced levels of various points at regular intervals along a line or set of lines?

Profile levelling Signup and view all the answers

What kind of telescope is externally focused by moving either the objective or eye piece?

External focusing telescope Signup and view all the answers

What is eliminated by making the lengths of two sides equal in a bubble tube?

Error due to Curvature Signup and view all the answers

What is the term for the type of levelling used when it's not possible to balance fore sight and back sight due to various errors?

Reciprocal levelling Signup and view all the answers