Correct Answer: D. All options are correct
Solution:
A positive error in chaining means the measured length is greater than the actual length. This occurs in several situations:
• Chain too short: If the chain is shorter than its standard length, it will take more chain lengths to cover a distance, resulting in a recorded length that is too high.
• Neglecting corrections: Slope and sag always make the measured distance along the ground or tape longer than the true horizontal distance. Failing to apply these (negative) corrections results in a final distance that is too large.
• Incorrect alignment: Measuring along a line that is not straight between two points will always result in a longer distance than the true straight-line distance.
Therefore, all the given options cause a positive error.
Correct Answer: D. All options are correct
Solution:
Chain surveying is a simple method of surveying, and its application is ideal under specific conditions. All the listed conditions are suitable for chain surveying:
• It works best on fairly level, open ground where linear measurements are easy to take.
• It is best suited for small areas because inaccuracies can accumulate over long distances.
• It is used when large-scale plans are needed, as it allows for direct measurement of details.
Therefore, all options are correct.
Correct Answer: B. ± 5mm
Solution:
According to survey standards (like the Indian Standard IS 1492:1970), the permissible tolerance for a 20-meter metric chain is ±5 mm. For a 30-meter chain, the tolerance is ±8 mm. This ensures the accuracy of measurements taken in the field.
Correct Answer: D. Both stepping method and hypotenusal method
Solution:
There are two main categories of methods for measuring on sloping ground:
• Direct Method: This is the "stepping method," where the chain is held horizontally in short segments.
• Indirect Methods: These involve measuring the slope distance and the angle of the slope to calculate the horizontal distance. The "hypotenusal allowance method" is one such technique. A clinometer is an instrument used to measure the slope angle for these indirect methods.
Since both the stepping and hypotenusal allowance methods are valid, option D is the most complete answer.
Correct Answer: C. 5
Solution:
In a standard metric chain, each link is 20 centimeters (or 0.2 meters) long. To find the number of links in one meter, you divide the total length (1 meter) by the length of a single link:
Number of links = 1 m / 0.2 m/link = 5 links.
Correct Answer: D. General layout of the chain lines
Solution:
The required accuracy of measurements is influenced by several factors:
• Length of the offset: Longer offsets are more prone to error, so higher accuracy is needed.
• Scale of plotting: A larger scale requires more precise measurements to be represented accurately.
• Importance of features: Critical features require more accurate location than minor ones.
However, the "general layout of the chain lines" relates to the principle of forming well-conditioned triangles, which ensures the strength and integrity of the overall survey framework, rather than the precision of any single measurement within it.
Correct Answer: A. Setting out right angles
Solution:
A cross-staff is a simple surveying instrument whose primary purpose is to set out lines perpendicular (at 90 degrees) to an existing chain line. This is essential for taking offsets. While it technically deals with a horizontal angle (90°), its function is for setting out, not for measuring various angles like a theodolite or compass.
Correct Answer: D. Indefinite feature to be surveyed
Solution:
The maximum permissible length of an offset is determined by factors that control accuracy. These include the desired accuracy of the work, the scale of the map (a small error is more noticeable on a large-scale map), and the precision of the instrument used for setting out the right angle. However, if the feature being located is itself indefinite or poorly defined (e.g., the edge of a marshy area), the precision of the offset's length is less critical, so this feature does not determine the limit.
Correct Answer: D. Indirect ranging
Solution:
Ranging is the process of establishing intermediate points on a straight line.
• Direct Ranging is used when the two end stations are intervisible.
• Indirect Ranging (also known as reciprocal ranging) is used when the two end stations are not visible to each other due to an obstruction like a hill. This method involves using intermediate points to establish the line.
Correct Answer: C. 100
Solution:
A Gunter's chain is a historic surveying tool with a total length of 66 feet. This length is divided into 100 links, making each link 0.66 feet (or 7.92 inches) long.
Correct Answer: A. 20 cm
Solution:
In a standard metric surveyor's chain, each link is 20 cm long. The links are connected by small oval or circular rings. Therefore, the distance between the centers of two adjacent rings (which defines the length of one link) is 20 cm.
Correct Answer: D. Check line
Solution:
A check line (or proof line) is a line measured in the field to check the accuracy of the survey framework. The length of the check line as measured on the ground should agree with its length on the plotted plan. A tie line joins subsidiary stations and helps in locating interior details, while the base line is the main and longest line upon which the framework is built.
Correct Answer: A. 30(1–cosθ)
Solution:
The correction for slope is the difference between the measured slope distance (L) and the true horizontal distance (H). The horizontal distance is calculated as H = L cos(θ). The correction, which must be subtracted from the measured length, is Cs = L - H = L - L cos(θ) = L(1 - cosθ). For a 30 m chain, this becomes 30(1 - cosθ).
Correct Answer: C. h²
Solution:
The approximate formula for slope correction is C ≈ h²/2L, where 'h' is the difference in elevation between the two ends of the chain and 'L' is the length of the chain. This formula shows that for a given chain length, the slope correction is directly proportional to the square of the difference in elevation (h²).
Correct Answer: A. Both chaining and ranging
Solution:
A building presents a physical barrier that obstructs both key activities in chain surveying:
• Chaining: It is impossible to stretch a chain or tape through the building to measure the distance.
• Ranging: It is impossible to see from a point on one side of the building to a point on the other side, making it impossible to establish a straight line between them.
Therefore, a building is an obstacle to both chaining and ranging.