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Past Questions
Which of the following is NOT an advantage of sprinkler irrigation?
A)
Suitable for undulating terrain
B)
Efficient water distribution
C)
Reduces soil erosion
D)
Low initial investment cost
Sprinkler irrigation is a pressurized irrigation system. To evaluate the options:
1. **Suitable for undulating terrain (Option a):** This is an advantage. Unlike surface irrigation, which requires precise land leveling, sprinklers can be used on uneven or sloping ground without causing massive runoff.
2. **Efficient water distribution (Option b):** This is an advantage. Sprinklers allow for precise control over the amount of water applied, reducing wastage compared to flood irrigation.
3. **Reduces soil erosion (Option c):** This is generally an advantage compared to furrow or flood irrigation on slopes, as it prevents the concentrated flow of water that strips topsoil (provided the application rate does not exceed the soil's infiltration rate).
4. **Low initial investment cost (Option d):** This is NOT an advantage; it is a major disadvantage. Sprinkler systems require significant capital for pumps, piping, nozzles, and control valves, making the initial setup cost much higher than traditional surface irrigation methods.
Therefore, option 'd' is the correct answer as it describes a disadvantage, not an advantage.
What is the primary benefit of using GPS in surveying?
A)
It eliminates the need for fieldwork
B)
It provides high-accuracy elevation measurements
C)
It allows real-time positioning with minimal effort
D)
It replaces all traditional surveying techniques
Step-by-step reasoning:
1. Analysis of GPS (Global Positioning System): GPS is a satellite-based navigation system that allows a receiver to determine its absolute position (latitude, longitude, and altitude) anywhere on Earth.
2. Evaluating Option (a): GPS does not eliminate fieldwork; a surveyor must still physically go to the site to place the receiver on the specific point being measured.
3. Evaluating Option (b): While GPS provides elevation, traditional leveling (using a dumpy level or auto-level) is significantly more accurate for vertical measurements than standard GPS, which often has a higher margin of error in the Z-axis (vertical) compared to the X and Y axes.
4. Evaluating Option (c): This is the primary benefit. GPS allows for 'Real-Time Kinematic' (RTK) positioning, enabling surveyors to obtain coordinates instantly without the need for complex manual chaining or triangulation between points, drastically reducing the effort and time required for establishing control points.
5. Evaluating Option (d): GPS does not replace all traditional techniques. For example, in dense forests or urban canyons (where satellite signals are blocked), traditional methods like Total Station or Theodolite surveying are still essential.
Conclusion: The most accurate primary benefit among the choices is the ability to achieve real-time positioning with significantly reduced manual effort compared to traditional traverse methods.
The most common type of error in levelling is:
A)
Instrumental error
B)
Gross error
C)
Collimation error
D)
Systematic error
In levelling, errors are generally classified into three categories: Instrumental, Personal (Gross), and Natural. Among these, the most common and significant instrumental error encountered in the field is the Collimation Error.
1. Collimation Error: This occurs when the line of sight (line of collimation) is not perfectly horizontal when the instrument is levelled. It is the most frequent error because the instrument can easily be knocked out of adjustment during transport or use. It is typically corrected by keeping the backsight and foresight distances equal or by using the two-peg test.
2. Instrumental Error (Option a): This is a broad category. While collimation error is a type of instrumental error, 'Collimation error' is the specific, most common type within this category.
3. Gross Error (Option b): These are caused by human carelessness (e.g., misreading a staff or recording a wrong value). While they happen, they are not 'systematic' or 'common' in the technical sense of instrument behavior.
4. Systematic Error (Option d): This is a general classification of errors that follow a mathematical or physical law (including collimation error). However, the question asks for the 'most common type', and in the context of levelling, the specific answer is the collimation error.
Using Dicken’s formula, estimate the peak discharge if the catchment area is 500 km² and the Dicken’s coefficient (C) is 25.
A)
1565 m³/s
B)
2643 m³/s
C)
2547 m³/s
D)
3070 m³/s
Option B is correct: 2643 m³/s.
Why is geodetic surveying necessary for large infrastructure projects?
A)
It simplifies the survey process
B)
It considers the earth’s curvature
C)
It reduces project costs
D)
It eliminates the need for levelling
Surveying is broadly divided into two categories: Plane Surveying and Geodetic Surveying.
1. Plane Surveying: Assumes the earth's surface to be a flat plane. This is acceptable for small areas (typically less than 250 sq km) because the effect of the earth's curvature is negligible.
2. Geodetic Surveying: Accounts for the true ellipsoidal or spherical shape of the earth. For large-scale infrastructure projects (such as national highways, long-distance pipelines, or state-wide irrigation networks), the curvature of the earth introduces significant errors if ignored. Therefore, geodetic surveying is necessary to maintain high precision over large distances.
Analysis of other options:
- Option (a) is incorrect because geodetic surveying is significantly more complex than plane surveying due to the advanced mathematics and instrumentation required.
- Option (c) is incorrect because geodetic surveying usually increases costs due to the need for specialized equipment (like GPS/GNSS) and expert personnel.
- Option (d) is incorrect because levelling is still a fundamental requirement for determining elevations, regardless of whether the horizontal control is plane or geodetic.
What is the primary focus of hydrology?
A)
Study of ocean currents
B)
Study of groundwater only
C)
Study of movement, distribution, and quality of water on Earth
D)
Study of air pressure and weather patterns
Hydrology is defined as the science that deals with the occurrence, circulation, distribution, and properties of water on Earth and its atmosphere. This includes the study of the hydrological cycle (precipitation, evaporation, transpiration, runoff, and infiltration), surface water (rivers, lakes), and groundwater.
Analysis of other options:
- Option (a) is incorrect because the study of ocean currents is specifically called 'Oceanography'.
- Option (b) is incorrect because groundwater is only one component of hydrology; the field also encompasses surface water and atmospheric water.
- Option (d) is incorrect because the study of air pressure and weather patterns is 'Meteorology'.
Which of the following best describes the primary function of a theodolite in surveying?
A)
Measuring horizontal and vertical angles with high precision
B)
Determining elevations and contours of land
C)
Measuring distances directly between two points
D)
Capturing digital survey data with automated processing
A theodolite is a precision instrument used in surveying primarily for the measurement of angles in both horizontal and vertical planes.
1. Why Option (a) is correct: The fundamental design of a theodolite consists of a telescope mounted on two perpendicular axes (horizontal and vertical), allowing the surveyor to measure horizontal angles (for triangulation and traversing) and vertical angles (for determining heights or slopes) with very high accuracy.
2. Why Option (b) is incorrect: Determining elevations and contours is the primary function of a Level (e.g., Dumpy level or Auto level). While a theodolite can be used for trigonometric leveling, it is not its primary defining function compared to a level.
3. Why Option (c) is incorrect: Measuring distances directly is the function of a tape, chain, or Electronic Distance Meter (EDM). A standard theodolite measures angles, not linear distances (unless it is a 'Total Station', which is a combination of a theodolite and an EDM).
4. Why Option (d) is incorrect: Capturing digital data with automated processing describes a Total Station or GPS/GNSS survey system. A traditional theodolite is an optical instrument used for manual readings.
What is the hydraulic radius of a trapezoidal channel with: Bottom width b=6m, Depth h=3m, Side slope m=1
A)
1.86m
B)
2.12m
C)
2.54m
D)
2.86m
To find the hydraulic radius (R) of a trapezoidal channel, we use the formula R = A / P, where A is the cross-sectional area and P is the wetted perimeter.
1. **Given Data:**
- Bottom width (b) = 6 m
- Depth (h) = 3 m
- Side slope (m) = 1 (Horizontal:Vertical = 1:1)
2. **Calculate Cross-sectional Area (A):**
The area of a trapezoid is given by: A = (b + m*h) * h
A = (6 + 1 * 3) * 3
A = (6 + 3) * 3 = 9 * 3 = 27 m²
3. **Calculate Wetted Perimeter (P):**
The wetted perimeter for a trapezoidal channel is: P = b + 2 * h * sqrt(1 + m²)
P = 6 + 2 * 3 * sqrt(1 + 1²)
P = 6 + 6 * sqrt(2)
P = 6 + 6 * 1.4142 = 6 + 8.4852 = 14.4852 m
4. **Calculate Hydraulic Radius (R):**
R = A / P
R = 27 / 14.4852
R ≈ 1.8639 m
Rounding to two decimal places, we get 1.86m. Therefore, option (a) is the correct answer.
The main source of irrigation in India is-
A)
Wells
B)
Canals
C)
Rainwater
D)
Lakes
In India, groundwater is the primary source of irrigation. This category includes both open wells and tube wells. According to data from the Ministry of Jal Shakti and various agricultural reports, groundwater (wells) accounts for approximately 60% to 65% of the total irrigated area in India, surpassing surface water sources.
Analysis of options:
- a. Wells: Correct. Tube wells and open wells are the most widely used irrigation methods across most Indian states due to their accessibility and reliability.
- b. Canals: Incorrect. While canals are a significant source of irrigation (especially in Northern India), they cover a smaller percentage of the total irrigated area compared to wells.
- c. Rainwater: Incorrect. Rainwater is the basis for 'rain-fed' agriculture, but by definition, 'irrigation' refers to the artificial application of water to land, making rainwater a source of moisture rather than a source of irrigation.
- d. Lakes: Incorrect. Lakes are not used as a primary systemic source of irrigation on a national scale in India.
A canal supplies 0.2 cumecs of water to a field continuously for 8 hours. Determine the volume of water supplied.
A)
5760 m³
B)
3600 m³
C)
4800 m³
D)
6000 m³
To determine the total volume of water supplied, we use the formula: Volume = Discharge × Time.
1. **Identify the given values:**
- Discharge (Q) = 0.2 cumecs. 'Cumec' stands for cubic meters per second (m³/s).
- Time (t) = 8 hours.
2. **Convert time into seconds:**
Since the discharge is given per second, the time must be converted to seconds to maintain unit consistency.
- 1 hour = 60 minutes
- 1 minute = 60 seconds
- Therefore, 8 hours = 8 × 60 × 60 = 28,800 seconds.
3. **Calculate the Volume (V):**
- V = Q × t
- V = 0.2 m³/s × 28,800 s
- V = 5,760 m³
Comparing this result to the options:
- Option (a) 5760 m³ matches our calculation.
- Option (b) 3600 m³ is incorrect.
- Option (c) 4800 m³ is incorrect.
- Option (d) 6000 m³ is incorrect.
The discharge (Q) in a rectangular channel is: Width of channel (b) = 3 m, Depth of flow (h) = 1.2 m, Velocity (V) = 1.5 m/s
A)
4.9 m³/s
B)
5.4 m³/s
C)
5.6 m³/s
D)
5.1 m³/s
To find the discharge (Q) in a rectangular channel, we use the continuity equation: Q = A × V, where 'A' is the cross-sectional area of the flow and 'V' is the average velocity of flow.
Step 1: Calculate the cross-sectional area (A) for a rectangular channel.
Area (A) = Width (b) × Depth of flow (h)
A = 3 m × 1.2 m = 3.6 m²
Step 2: Calculate the discharge (Q).
Discharge (Q) = Area (A) × Velocity (V)
Q = 3.6 m² × 1.5 m/s = 5.4 m³/s
Comparing this result to the given options:
- Option (a) 4.9 m³/s is incorrect.
- Option (b) 5.4 m³/s matches our calculation.
- Option (c) 5.6 m³/s is incorrect.
- Option (d) 5.1 m³/s is incorrect.
How does a total station improve accuracy in surveying compared to a theodolite?
A)
It reduces the need for manual calculations
B)
It can measure underground features
C)
It works without needing a reference point
D)
It automatically adjusts for atmospheric conditions
A Total Station is an electronic/optical instrument that integrates an Electronic Distance Meter (EDM), an electronic theodolite, and an onboard microprocessor.
1. Why Option (a) is correct: In traditional theodolite surveying, the surveyor must manually read angles and distances (often using a tape or stadia hairs) and then perform trigonometric calculations (like sine and cosine rules) to determine the coordinates (X, Y, Z) of a point. A Total Station performs these calculations automatically and instantaneously using its internal microprocessor, which significantly reduces human error associated with manual data recording and computation, thereby improving the overall accuracy and efficiency of the survey.
2. Why Option (b) is incorrect: Total stations use light/infrared waves (EDM) which cannot penetrate the ground; they cannot measure underground features.
3. Why Option (c) is incorrect: Like any surveying instrument, a Total Station requires a known reference point (station) and a known orientation (back-sight) to establish a coordinate system.
4. Why Option (d) is incorrect: While some high-end Total Stations allow the user to input atmospheric corrections (temperature and pressure), they do not 'automatically' adjust for these conditions without input or calibration; furthermore, this is a refinement of measurement rather than the primary fundamental improvement in accuracy/workflow over a theodolite.
The process of artificially supplying water to land for agricultural purposes is called-
A)
Drainage
B)
Irrigation
C)
Evaporation
D)
Infiltration
The question asks for the term describing the artificial application of water to land for agriculture.
1. **Irrigation (Option b):** This is the correct term. Irrigation is the artificial process of applying water to soil or land to assist in the production of crops, especially in areas where rainfall is insufficient.
2. **Drainage (Option a):** This is the opposite of irrigation; it is the natural or artificial removal of excess surface and sub-surface water from an area.
3. **Evaporation (Option c):** This is a physical process where liquid water changes into water vapor and rises into the air; it is a loss of water from the soil/plant system.
4. **Infiltration (Option d):** This is the process by which water on the ground surface enters the soil profile.
What is the significance of the Base Period of a crop?
A)
It determines the time between sowing and harvesting
B)
It is the total period from first to last irrigation
C)
It defines the period of highest water demand in a crop cycle
D)
It represents the time taken for root development
In irrigation engineering, the 'Base Period' (B) is formally defined as the time elapsed between the first watering of a crop and the last watering of that crop. It is a critical parameter used to calculate the 'Delta' (total depth of water required by a crop) and the duty of water.
Analysis of options:
- Option (a) is incorrect because the time between sowing and harvesting is known as the 'Crop Period'. The base period is usually shorter than the crop period because irrigation is not required immediately after sowing or immediately before harvesting.
- Option (b) is correct as it matches the technical definition of the Base Period.
- Option (c) is incorrect because the period of highest water demand is referred to as the 'critical period' or 'peak demand period'.
- Option (d) is incorrect as root development is a biological growth phase and not a measurement of the irrigation schedule duration.
Which is the most water-efficient irrigation method?
A)
Furrow irrigation
B)
Sprinkler irrigation
C)
Drip irrigation
D)
Flood irrigation
Water efficiency in irrigation is measured by the percentage of water that actually reaches the root zone of the plant versus the amount applied.
1. **Drip Irrigation (c):** This is the most efficient method (often >90% efficiency). It delivers water slowly and precisely to the root zone through a network of valves, pipes, and emitters. This minimizes losses due to evaporation, surface runoff, and deep percolation.
2. **Sprinkler Irrigation (b):** While more efficient than surface methods, it is less efficient than drip irrigation (typically 70-85%). Water is lost to wind drift and evaporation as it travels through the air.
3. **Furrow Irrigation (a):** A type of surface irrigation where water flows in small parallel channels. It is less efficient (typically 40-60%) due to significant losses from deep percolation and runoff at the end of the furrows.
4. **Flood Irrigation (d):** The least efficient method. Water is applied over the entire field surface, leading to massive losses through evaporation and deep percolation (typically 30-50% efficiency).
If a river has a cross-sectional area of 30 m² and the velocity of flow is 2 m/s, what is the discharge?
A)
30 m³/s
B)
50 m³/s
C)
60 m³/s
D)
90 m³/s
To find the discharge of a river, we use the Continuity Equation for steady flow.
1. **Formula**: Discharge (Q) is the product of the cross-sectional area (A) and the average velocity of flow (v).
Formula: Q = A × v
2. **Given Data**:
- Cross-sectional area (A) = 30 m²
- Velocity of flow (v) = 2 m/s
3. **Calculation**:
Q = 30 m² × 2 m/s = 60 m³/s
4. **Analysis of Options**:
- Option (a) 30 m³/s: Incorrect; this only considers the area without multiplying by velocity.
- Option (b) 50 m³/s: Incorrect; result of an incorrect calculation.
- Option (c) 60 m³/s: Correct; matches the calculated discharge.
- Option (d) 90 m³/s: Incorrect; result of an incorrect calculation.
Contour lines that are very close together indicate:
A)
Flat terrain
B)
A steep slope
C)
A river valley
D)
A depression in the land
In surveying, a contour line is an imaginary line connecting points of equal elevation. The horizontal distance between two contour lines represents the change in elevation over that distance.
1. **Steep Slope:** When contour lines are drawn very close together, it means that the elevation is changing rapidly over a very short horizontal distance, which characterizes a steep slope.
2. **Flat Terrain:** Conversely, when contour lines are spaced far apart, it indicates that the elevation changes slowly over a large distance, representing flat or gentle terrain.
3. **River Valley:** A river valley is typically represented by V-shaped contours with the apex pointing upstream (towards higher ground).
4. **Depression:** A depression is indicated by closed contour lines with hachure marks (small ticks) pointing inwards toward the center of the depression.
Which formula is used to calculate the velocity of flow in an open irrigation canal?
A)
Bernoulli’s equation
B)
Chezy’s formula
C)
Darcy’s law
D)
Reynolds number
Step-by-step reasoning:
1. The question asks for the formula used to calculate the velocity of flow in an open irrigation canal. Open channel flow is driven by gravity and is characterized by a free surface.
2. Chezy's formula is one of the fundamental equations used in hydraulics to calculate the mean velocity (V) of flow in an open channel. It is expressed as V = C√(RS), where C is the Chezy coefficient, R is the hydraulic radius, and S is the slope of the energy grade line (or bed slope).
3. Manning's formula is a more common derivation of Chezy's formula, but among the given options, Chezy's is the only one applicable to open channel velocity.
Analysis of other options:
- a. Bernoulli’s equation: This is a general energy conservation equation for fluid flow along a streamline, used to find pressure or velocity at a point, but not specifically for calculating the average velocity of an open canal based on its geometry and slope.
- c. Darcy’s law: This describes the flow of a fluid through a porous medium (like soil or sand), not open channel flow.
- d. Reynolds number: This is a dimensionless quantity used to determine whether a flow is laminar or turbulent; it is not a formula to calculate the velocity of flow itself.
Which of the following factors has the most direct and immediate impact on runoff generation?
A)
Land slope
B)
Soil type
C)
Vegetation cover
D)
Rainfall intensity
Runoff generation is primarily governed by the relationship between the rate at which water is supplied to the surface and the rate at which the soil can absorb it (infiltration capacity).
1. **Rainfall Intensity (Correct):** This is the most direct and immediate factor. According to the concept of 'Horton Overland Flow', if the rainfall intensity exceeds the infiltration capacity of the soil, runoff is generated immediately. Even in highly permeable soils, an extremely high rainfall intensity can trigger immediate runoff.
2. **Land Slope (Incorrect):** Slope affects the velocity of runoff and the time it takes to reach a stream, but it is a static physical characteristic. It influences the process but does not 'trigger' the generation of runoff in the same immediate way as a rain event.
3. **Soil Type (Incorrect):** Soil type determines the infiltration capacity (e.g., sandy soil has high infiltration, clay has low). While critical, it is a baseline condition. Runoff only occurs when the rainfall intensity interacts with this capacity.
4. **Vegetation Cover (Incorrect):** Vegetation intercepts rainfall and slows down surface flow, increasing the time available for infiltration. Like soil type, this is a modifying factor rather than the immediate driver of the runoff event.
Why does sandy soil require more frequent irrigation than clayey soil?
A)
Sandy soil has a lower infiltration rate
B)
Sandy soil has a lower water-holding capacity
C)
Clayey soil allows rapid water movement
D)
Clayey soil loses more water due to evaporation
The frequency of irrigation is primarily determined by the soil's ability to retain water against the force of gravity (water-holding capacity).
1. **Sandy Soil:** Composed of large particles with large macropores. While this allows for high infiltration rates, it means the soil cannot hold onto water effectively. Water drains quickly through the profile, leading to a low water-holding capacity. Consequently, the root zone dries out faster, requiring more frequent irrigation.
2. **Clayey Soil:** Composed of very small particles with tiny micropores. These small pores create strong capillary forces that hold water tightly. Therefore, clayey soil has a high water-holding capacity and requires less frequent irrigation.
Analysis of other options:
- Option (a) is incorrect because sandy soil actually has a *higher* infiltration rate than clayey soil.
- Option (c) is incorrect because clayey soil restricts water movement due to low permeability; sandy soil allows rapid movement.
- Option (d) is incorrect because evaporation is more dependent on surface area and climate; clayey soils often retain moisture longer, reducing the relative rate of depletion compared to sandy soils.
Which of the following irrigation methods is best suited for sandy soil?
A)
Sprinkler irrigation
B)
Drip irrigation
C)
Flood irrigation
D)
Furrow irrigation
Step-by-step reasoning: 1. Analysis of Sandy Soil: Sandy soils have large particles and large pore spaces, leading to high infiltration rates and low water-holding capacity. Water percolates downward very quickly (high permeability). 2. Evaluating Flood and Furrow Irrigation: These are surface irrigation methods. In sandy soil, water sinks rapidly into the ground before it can move laterally to cover the field, leading to massive water wastage and uneven distribution. 3. Evaluating Drip Irrigation: While highly efficient, drip irrigation is primarily used for high-value crops or water-scarce regions. In very sandy soils, the 'wetting bulb' becomes narrow and deep rather than wide, which may require very close emitter spacing to be effective. 4. Evaluating Sprinkler Irrigation: Sprinkler irrigation applies water in a manner similar to rainfall. Because it allows for frequent, light applications of water, it prevents the deep percolation losses associated with surface irrigation. It is specifically recommended for sandy soils because it can match the application rate to the soil's infiltration rate more effectively than surface methods, ensuring the root zone is adequately moistened without wasting water. Therefore, sprinkler irrigation is the most suitable general method for sandy soils.
If a rain gauge recorded 50 mm of rainfall in 10 hours, what is the average intensity of rainfall?
A)
2.5 mm/hr
B)
5 mm/hr
C)
7.5 mm/hr
D)
10 mm/hr
The average intensity of rainfall is defined as the total depth of rainfall recorded divided by the total duration of the rainfall event.
Given:
- Total Rainfall (P) = 50 mm
- Total Duration (t) = 10 hours
Formula:
Average Intensity (I) = Total Rainfall / Total Duration
I = 50 mm / 10 hours
I = 5 mm/hr
Comparing this result to the options:
- Option (a) 2.5 mm/hr is incorrect (result of 25/10).
- Option (b) 5 mm/hr is correct.
- Option (c) 7.5 mm/hr is incorrect.
- Option (d) 10 mm/hr is incorrect (result of 100/10).
What does Dicken’s formula estimate?
A)
The rainfall intensity
B)
The peak flood discharge in a catchment
C)
The evaporation rate
D)
The infiltration rate
Dickens' formula is an empirical formula used in hydrology to estimate the peak flood discharge (peak runoff) of a catchment area, particularly in regions where rainfall data is scarce. The formula is expressed as Q = C * A^(3/4), where 'Q' is the peak discharge, 'C' is Dickens' constant (which varies based on the region and climate), and 'A' is the catchment area.
Analysis of other options:
- Option (a) Rainfall intensity is typically measured using rain gauges or estimated via Intensity-Duration-Frequency (IDF) curves.
- Option (c) Evaporation rate is measured using evaporation pans or estimated via Penman's equation.
- Option (d) Infiltration rate is measured using infiltrometers or estimated via Horton's equation.
Which type of traversing is best suited for an area with multiple obstacles?
A)
Open traverse
B)
Closed traverse
C)
Radial traverse
D)
Triangulation
In surveying, traversing is the process of establishing a series of connected lines.
1. **Closed Traverse (Correct):** A closed traverse starts and ends at the same point or connects two known points. Because it forms a loop or a closed circuit, it allows the surveyor to calculate the 'closing error' (the difference between the measured and theoretical coordinates). In areas with multiple obstacles, the surveyor can deviate the path of the traverse to bypass these obstacles while still maintaining the ability to check for accuracy and correct errors through balancing. This makes it the most reliable and best-suited method for complex terrains.
2. **Open Traverse:** An open traverse does not return to the starting point or close on a known point. It is used for linear projects like roads or railways. Because there is no closing point, there is no way to check for cumulative errors in measurement, making it unsuitable for areas where obstacles force frequent changes in direction.
3. **Radial Traverse:** This involves taking measurements from a single central point to various surrounding points. It is only effective for small, open areas where the central point has a clear line of sight to all other points. Obstacles would block the line of sight, making this method impractical.
4. **Triangulation:** While highly accurate for large areas, triangulation relies on the measurement of angles in a network of triangles. It requires clear inter-visibility between stations. In an area with multiple obstacles, establishing these clear lines of sight for large triangles is often impossible.
Which method is NOT a technique of contouring?
A)
Direct method
B)
Indirect method
C)
Compass method
D)
Grid method
Contouring is the process of determining the layout of a surface by joining points of equal elevation. There are two primary methods of contouring:
1. Direct Method: In this method, the points on the contour lines are located directly in the field using a level and a staff. It is highly accurate but very time-consuming.
2. Indirect Method: In this method, a grid or a series of cross-sections is established, and the elevations of these points are determined. The contour lines are then interpolated between these points in the office. Common techniques under the indirect method include:
- Grid method (or Square method)
- Cross-section method
- Radial line method
Comparing the options:
- Option (a) Direct method is a standard technique.
- Option (b) Indirect method is the broad category of techniques.
- Option (d) Grid method is a specific type of indirect contouring.
- Option (c) Compass method is used for measuring directions (bearings) and plotting horizontal layouts (traversing), but it cannot measure elevations (vertical distance), which is the fundamental requirement for contouring. Therefore, it is NOT a technique of contouring.