Correct Answer: A. Linear measurements only
Solution:
Chain surveying is the simplest type of surveying in which only linear measurements are taken in the field. All angular measurements are plotted indirectly. The primary equipment used are the chain or tape for measuring distances, and arrows and ranging rods for marking points and lines. No angle measuring instruments are used.
Correct Answer: D. it is possible to set offsets correctly on both sides
Solution:
In surveying, offsets are always measured horizontally and perpendicular to the chain line. Even if the ground is sloping in the E-W direction (perpendicular to the N-S chain line), the horizontal distance for the offset can be measured correctly. This is achieved by holding the tape horizontally and using a plumb bob to transfer the point down to the sloping ground. This procedure works equally well on both the east and west sides of the chain line.
Correct Answer: C. Decreases with increase of slope
Solution:
When measuring on sloping ground using the "stepping" method, the chain or tape is held horizontally in short lengths. As the slope of the ground increases (becomes steeper), the length of each horizontal "step" that can be practically measured becomes shorter. To maintain accuracy and keep the tape level, the surveyor must use smaller increments. Therefore, the distance between steps decreases as the slope increases.
Correct Answer: C. 30(cosθ–1) m
Solution:
When a distance 'L' is measured along a slope of angle θ, the true horizontal distance 'H' is given by H = L cos(θ). The measured length (L=30m) is always longer than the horizontal length. The correction for slope (Cs) is the difference between the horizontal distance and the measured slope distance.
Cs = H - L
Cs = L cos(θ) - L
Cs = L(cosθ – 1)
Substituting L = 30m, we get:
Cs = 30(cosθ – 1) m
Since cos(θ) is always less than or equal to 1, this correction is always negative or zero, as it should be.
Correct Answer: A. 1.5α²/100
Solution:
This is a common field approximation formula used for calculating slope correction when the angle of the slope is given in degrees. The correction (in links) for a 100-link chain is found using the formula C ≈ 1.5α²/100, where α is the vertical angle of the slope in degrees. This formula provides a quick way to estimate the correction without trigonometric calculations in the field.
Correct Answer: C. French cross staff
Solution:
A French cross staff is a surveying instrument used for setting out right angles (90°) and 45° angles. It consists of two pairs of vertical slits arranged at right angles and at 45° to each other, making it ideal for this purpose. An Open cross staff and optical square are primarily used for setting out 90° angles only.
Correct Answer: B. Proportional to the square root of the length of the line
Solution:
Compensating errors are accidental and random. They can be positive or negative and tend to cancel each other out over a series of measurements. According to the theory of errors, the total compensating error in chaining is proportional to the square root of the length of the line (E ∝ √L). Cumulative errors, on the other hand, are proportional to the length of the line (E ∝ L).
Correct Answer: D. Any of the options
Solution:
If a chain is found to be too short, its length needs to be increased. This can be achieved by several methods:
• Straightening the links: If any links are bent, straightening them will increase the chain's overall length.
• Inserting additional circular rings: Adding new rings at the joints will increase the total length.
• Flattening the circular rings: Flattening the existing rings will make them longer, thus increasing the chain's length.
Therefore, any of these methods can be used to correct a short chain.
Correct Answer: A. Nickel and steel
Solution:
Invar tapes are known for their extremely low coefficient of thermal expansion, making them ideal for high-precision surveying work. They are made from an alloy of steel (about 64%) and nickel (about 36%). This specific composition minimizes changes in length due to temperature variations.
Correct Answer: C. Five chains
Solution:
In standard chaining procedure, a set of 10 arrows is used. The leader moves ahead and inserts an arrow into the ground at the end of each chain length. The follower picks up these arrows as they proceed. The number of arrows held by the follower indicates the number of full chain lengths that have been measured from the starting point. Therefore, if the follower has five arrows, it means five chain lengths have been completed.
Correct Answer: A. Along a chain line
Solution:
Chainage refers to the cumulative distance measured along a survey line, such as a chain line or baseline, from the starting point or point of zero. It is a fundamental measurement in linear surveying methods like chain surveying.
Correct Answer: D. Reconnaissance
Solution:
The first and most crucial step in any survey project is reconnaissance. This involves a preliminary inspection of the area to be surveyed to understand the terrain, identify potential obstacles, select suitable locations for survey stations, and plan the overall framework of the survey. All other steps follow after this initial planning phase.
Correct Answer: B. Small surveys in open ground
Solution:
Chain surveying is most suitable for small, relatively flat, open areas with simple details and few obstacles. Its reliance on linear measurements makes it inefficient and inaccurate for large areas or areas with dense details, difficult terrain, or many obstructions where triangulation or other methods would be more appropriate.
Correct Answer: A. 150
Solution:
A standard metric chain has a link length of 20 cm (0.2 m). To find the number of links in a 30-meter chain, you divide the total length by the length of one link:
Number of links = 30 m / 0.2 m/link = 150 links.
Correct Answer: D. All options are correct
Solution:
When an obstacle prevents direct measurement along a chain line, various geometric methods are used to bypass it and continue the line. These methods include:
• Setting up perpendiculars to create a rectangle around the obstacle.
• Using geometric principles and the solution of triangles (e.g., similar triangles) to calculate the obstructed distance.
• Using an instrument like a cross-staff or optical square to make angular measurements (typically 90°) to bypass the object.
All these techniques are valid for prolonging a chain line.