57 Questions
What correction is applied to linear measurements to account for the extension of the chain or tape?
Pull correction
If the field temperature is less than the standardized temperature, what is the nature of error and correction in temperature correction?
Error: positive, Correction: negative
In temperature correction, if the coefficient of linear expansion is higher, what happens to the recorded length compared to the actual length?
Recorded length is less than actual length
Which correction is made when the difference between pull force and standard pull is considered in linear measurements?
Pull correction
What is the nature of error and correction when the pull force is less than the standard pull in pull correction?
Error: positive, Correction: negative
In linear measurements, if Young’s modulus of elasticity of the material increases, what happens to the extension of the chain or tape?
Extension increases
What is the term used to describe the sag correction in the tape or chain measurement?
Catenary
Why was triangulation historically preferred for establishing control points?
It was easier to measure angles than distances
What type of triangles were primary trig points fixed at in triangulation networks?
Equilateral triangles
What was the reduction in observational accuracy when transitioning from primary to secondary triangulation networks?
-20%
How were the base lines measured in classical triangulation?
By invar tapes in catenary
What does the scale error in triangulation refer to?
Error resulting from incorrect base line measurement
Where are control stations typically situated in urban areas for roof-top triangulation?
On accessible buildings' roofs
What is the main requirement for conducting successful triangulation in open, hilly country?
'Long, uninterrupted sight lines'
What is the purpose of the up-and-down movement of the prism in a prismatic compass?
To provide an adjustment for focusing
Why are dark glasses swung in front of the back vane in a prismatic compass?
To aid in solar observations
What is the function of the lifting pin and lifting lever in a prismatic compass?
To lift the magnetic needle out of pivot point
Why is a mirror located in front of the forward vane in a prismatic compass?
To assist in solar observations
Which component of a prismatic compass is used to read graduations on the graduated ring?
Prism
What is the purpose of the reflecting mirror in a prismatic compass?
To get an image of an object located above or below instrument level while bisection
Why are slightly convex faces used for the 45º reflecting prism within a prismatic compass?
To magnify the image of the graduations
What is carried on a mounting that can be moved up and down between slides fixed on the outside of a prismatic compass case?
Prism
What is viewed through a small circular aperture in the prism mounting of a prismatic compass?
The vertical wire
Why are dark glasses swung in front of the back vane when solar observations are being taken?
To reduce glare
What is the method used when the end stations are not visible from intermediate points when a jungle area obstructs the chain line?
Reciprocal ranging
In compass survey, how are the directions of survey lines typically measured?
By using a magnetic compass
What is a typical example of an obstacle that obstructs chaining but not ranging?
Water bodies like lakes and rivers
Which instrument is generally used for the rapid filling of detail in larger surveys and explanatory works?
Prismatic compass
What should be ensured to avoid errors when using a compass survey?
Presence of magnetic disturbances
What type of survey is preferred when the area to be surveyed is small but a high degree of accuracy is desired?
Chain survey
What is the main function of ensuring the best positions for survey stations?
Economy of observation
Why are braced quadrilaterals considered advantageous in surveying?
They provide more conditions of adjustment
In triangulation, what method would inevitably be used?
Method of directions
What is essential for a target used in surveying?
Capable of being accurately centered over the survey point
What should be done if there are angles less than 25°?
Ensure they are situated opposite a side not entering into scale computation
What should be done to ensure ground is satisfactory for long-term survey stations construction?
Study soil conditions
Why might signal lamps be used as targets in highly precise networks?
They are suitable for night observations
What is the purpose of the spring brake or brake pin when using a prismatic compass?
To dampen the oscillation of the needle
How is centering checked when using a prismatic compass?
By adjusting the legs of the tripod
What is the aim of leveling the compass in surveying?
To freely swing the graduated circular ring
How can focusing be achieved when using a prismatic compass?
By moving the prism up or down
What causes the largest variation in magnetic declination?
Secular Variation
What does diurnal variation refer to in terms of magnetic declination?
A swing of the compass needle about its mean daily position
What is a magnetic bearing in surveying?
The angle between magnetic meridian and survey line direction
How does a magnetic meridian differ from a true meridian?
Magnetic meridians follow earth's magnetic field, true meridians do not
What characteristic defines a surveyor's compass?
Use for determining magnetic bearing with chain or compass survey
What role does a spring brake play when using a prismatic compass?
To stabilize and stop needle oscillation for a quick reading
In compass surveying, what is the main difference between true bearing and magnetic bearing?
True bearing is measured clockwise from true north, magnetic bearing is measured clockwise from magnetic north
If a fore bearing is 120 degrees, what would the corresponding back bearing be according to the general rule?
240 degrees
What is the relationship between back bearing (BA) and forward bearing (FB) when an observer relocates to another point?
BA = FB - 180 degrees
When traversing with a compass survey, what is done at each point to ensure accuracy?
Reading the compass and taking a back bearing
What does the Whole Circle Bearing System (W.C.B.) measure?
Bearing of survey lines wrt north or south line in a clockwise direction
In the Quadrantal Bearing System (Q.B.), how are bearings of survey lines measured?
Wrt north or south line whichever is nearest in a clockwise or anticlockwise direction
What is a Reduced Bearing (R.B.) in compass surveying?
Conversion of whole circle bearing into quadrantal bearing
If a survey line has a Whole Circle Bearing (W.C.B.) of 30 degrees in the first quadrant, what would be its Reduced Bearing (R.B.)?
-30 degrees
What would be the Quadrantal Bearing for a survey line with W.C.B. of 240 degrees in the fourth quadrant?
-60 degrees
'What action should be taken if a Forward Bearing (FB) measures 290 degrees during traversing?' According to the general rule:
+180 to get Back Bearing (BB)
Test your knowledge on corrections to linear measurements with a chain or tape including pull correction, temperature correction, standard length correction, sag correction, slope correction, and mean sea level correction. Explore how these corrections are applied for accurate measurements.
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