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Questions and Answers
What is the primary method of measuring distance used for reconnaissance surveys?
What is the primary method of measuring distance used for reconnaissance surveys?
Which instrument is designed to automatically record the number of paces taken?
Which instrument is designed to automatically record the number of paces taken?
What factors can affect the length of a person's pace according to the content?
What factors can affect the length of a person's pace according to the content?
Which device is best suited for measuring distance with a smooth route?
Which device is best suited for measuring distance with a smooth route?
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What mechanism does an odometer use to determine distance?
What mechanism does an odometer use to determine distance?
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What is a key feature of the perambulator for measuring distance?
What is a key feature of the perambulator for measuring distance?
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Which method is described as being very rough for determining distance?
Which method is described as being very rough for determining distance?
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How does a pedometer differ from a passometer?
How does a pedometer differ from a passometer?
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What is the primary reason that a slight deviation from the line affects pacing accuracy?
What is the primary reason that a slight deviation from the line affects pacing accuracy?
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What must be ensured before applying proper tension to the tape during measurement?
What must be ensured before applying proper tension to the tape during measurement?
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Which accessory is used to maintain horizontal alignment during distance measurement?
Which accessory is used to maintain horizontal alignment during distance measurement?
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In tachymetry, what is the primary method used to compute distances?
In tachymetry, what is the primary method used to compute distances?
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What is an essential factor affecting the precision of the stadia method?
What is an essential factor affecting the precision of the stadia method?
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Who introduced the stadia method in 1771?
Who introduced the stadia method in 1771?
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What physical characteristic of the equipment is crucial for stadia measurements?
What physical characteristic of the equipment is crucial for stadia measurements?
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Which of the following could lead to inaccuracies when using the tachymetric method?
Which of the following could lead to inaccuracies when using the tachymetric method?
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What is the first step in the procedure of taping for measuring distance?
What is the first step in the procedure of taping for measuring distance?
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Which type of error is due to the physical condition of the tape such as kinks or defects?
Which type of error is due to the physical condition of the tape such as kinks or defects?
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When measuring the horizontal distance from a slope, which formula correctly applies the zenith angle?
When measuring the horizontal distance from a slope, which formula correctly applies the zenith angle?
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What should a surveyor do if the measuring tape is found to be longer than the actual distance?
What should a surveyor do if the measuring tape is found to be longer than the actual distance?
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Which procedure involves ensuring that the tape remains level with respect to the ground?
Which procedure involves ensuring that the tape remains level with respect to the ground?
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Which of the following is NOT a step involved in the process of tapping distances?
Which of the following is NOT a step involved in the process of tapping distances?
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When measuring distance between two existing points, how should a short tape be handled?
When measuring distance between two existing points, how should a short tape be handled?
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What kind of error can occur due to environmental conditions such as temperature or wind?
What kind of error can occur due to environmental conditions such as temperature or wind?
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What is the most probable value (mpv) based on a series of measurements?
What is the most probable value (mpv) based on a series of measurements?
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In surveying, horizontal distance is defined as:
In surveying, horizontal distance is defined as:
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Which of the following methods is NOT listed as a technique of distance measurement?
Which of the following methods is NOT listed as a technique of distance measurement?
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What must be done to determine an individual's pace factor for distance pacing?
What must be done to determine an individual's pace factor for distance pacing?
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Which of the following statements about pacing as a measurement technique is FALSE?
Which of the following statements about pacing as a measurement technique is FALSE?
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Which of the following is an example of horizontal distance measurement?
Which of the following is an example of horizontal distance measurement?
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What is one advantage of using tachymetry in distance measurement?
What is one advantage of using tachymetry in distance measurement?
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Why is it important to walk naturally while calibrating one’s pace?
Why is it important to walk naturally while calibrating one’s pace?
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What is the primary requirement for the line of sight when using the stadia method?
What is the primary requirement for the line of sight when using the stadia method?
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In the equation D = Ks + C used in the stadia method, what does K represent?
In the equation D = Ks + C used in the stadia method, what does K represent?
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What is the purpose of the subtense bar method in distance measurement?
What is the purpose of the subtense bar method in distance measurement?
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Which of the following instruments is NOT typically used for measuring distances mechanically?
Which of the following instruments is NOT typically used for measuring distances mechanically?
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In photogrammetry, what type of photographs are used for making measurements?
In photogrammetry, what type of photographs are used for making measurements?
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What measurement technique involves pacing to ascertain distances?
What measurement technique involves pacing to ascertain distances?
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What is the length of the subtense bar used for distance measurement?
What is the length of the subtense bar used for distance measurement?
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Which method employs trigonometric functions for distance determination?
Which method employs trigonometric functions for distance determination?
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Study Notes
Introduction to Surveying
- Surveying is a field of engineering that involves determining the precise relative positions of points on the Earth's surface.
Methods of Measuring Distance
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Direct Measurement:
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Pacing is an approximate method used in reconnaissance surveying. It involves counting steps while walking a given distance.
- The average length of a step depends on the individual, age, height, physical condition, and the terrain.
- Passometer is a pocket instrument that automatically records the number of paces.
- Pedometer is similar to a passometer but registers the distance walked.
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Odometer measures distance by counting the revolutions of a wheel.
- This is often used to measure distances traveled by vehicles.
- Speedometer can be used to approximate distance by measuring speed and time traveled.
- Perambulator measures distance automatically using a single wheel and a dial.
- Judging Distance: This method is a rough estimation based on experience.
- Time Measurement: A rough estimate of distance can be obtained by knowing the average time taken to travel a certain distance by walking or horseback.
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Pacing is an approximate method used in reconnaissance surveying. It involves counting steps while walking a given distance.
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Chaining:
- The most common method of measuring distance, using a chain or steel tape.
- Chains are adequate for general surveying work. Steel tapes are used for greater precision.
Measurement of Distance: Chaining
- Chaining involves using a chain (or steel tape) to measure distance.
- The most common methods used for chaining are:
- Determining the distance between two points
- Laying out a known distance between two points
Steps in Chaining
- Lining in: Establishing a straight line between two points.
- Applying Tension: Holding the chain taut while measuring.
- Plumbing: Ensuring the tape is level and horizontal while measuring.
- Marking Tape Lengths: Placing pins at each full tape length.
- Reading the Tape: Interpreting distances on the graduated tape.
- Recording the Distance: Noting the total distance measured.
Slope Measurements
- On slopes, measurements are typically taken horizontally.
- There are two scenarios:
- Measurements are made directly along the slope, but the vertical or zenith angle needs to be calculated.
- The horizontal distance is calculated from the slope distance with trigonometric functions.
Taping Error
- Instrumental Error: Errors caused by defects in the tape itself, such as variations in length.
- Natural Error: Variations in tape length caused by environmental factors like temperature, wind, and stretching due to weight (sag).
- Personal Error: Caused by human error like careless chain handling, incorrect pin placement, misreadings, etc.
Tape Error Correction
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Measuring between two existing points:
- If the tape is longer than the standard length, the measured distance will be shorter. Add a correction.
- If the tape is shorter than the standard length, the measured distance will be longer. Subtract a correction.
Most Probable Value
- The most probable value of a measurement is the arithmetic mean (average).
- The most probable value is considered closest to the true value when repeated measurements are made under similar conditions.
Measurement of Horizontal Distances
- Determining precise horizontal distance is a fundamental operation in surveying.
- When points are at different elevations, the horizontal distance is measured between plumb lines at the points.
Types of Distances
- Vertical: Height difference between two points.
- Horizontal: The shortest distance between two points projected onto a level plane.
- Slope: The distance measured along an inclined line.
Techniques of Distance Measurement
- Pacing: Counting steps to determine distance.
- Taping: Using a chain or steel tape for measuring distances.
- Tachymetry: Measuring distances indirectly using instruments like transits or theodolites.
- Graphical and Mathematical Methods: Utilizing graphic and mathematical techniques like Pythagorean Theorem and trigonometry.
- Mechanical Devices: Using specialized devices such as passometers, pedometers, odometers, and speedometers.
- Photogrammetry: Measuring distances from images captured by cameras, often used in aerial surveying.
Distance by Pacing
- Pace Factor: The average length of an individual's step.
- To determine your pace factor, walk a known distance and count the number of paces taken.
- Accuracy in pacing is dependent on factors like pace length consistency, terrain, and walking speed.
Distance by Taping
- Taping is a common method of measuring distances using a chain or steel tape.
- The accuracy of taping depends on the quality of the tape, the skills of the person performing the measurement, and the precautions taken.
Taping Steps
- Ensure the tape is free of loops.
- Prepare the ground for marking points.
- Apply proper tension to the tape while measuring.
- Mark points with stakes or other markers.
- Read and record the distances measured.
Taping Accessories
- Plumb Bob: Used for aligning points and ensuring the tape is horizontal.
- Hand Level: Assists in keeping the tape level while measuring.
Distance by Tachymetry
- Tachymetry or tacheometry measures distances indirectly using optical geometry.
- It involves using instruments (like a transit or theodolite) to determine angles and subtense intervals on a graduated rod.
- These observations are then used in trigonometric calculations to calculate distances.
Stadia Method
- A rapid technique within tachymetry that utilizes a telescope with stadia hairs and a graduated rod.
- The stadia method enables quick horizontal distance calculations.
- The stadia constant (C) and the stadia interval factor (K) are essential for calculating distances.
- The equation D = Ks + C is used to compute the distance (D) based on the stadia interval (s).
Subtense Bar Method
- Uses a precisely measured bar (typically 2 meters long) with target marks at each end.
- The distance is measured by the angle subtended by the bar at the instrument.
- The bar is accurately positioned and the angle is measured with a theodolite or transit.
Distance by Graphical and Mathematical Methods
- Distance Formula: Using coordinates of two points to calculate distance.
- Pythagorean Theorem: Calculating the distance with a right triangle and the lengths of its sides.
- Trigonometric Functions: Using sine, cosine, and tangent functions to calculate distance.
- Plotting Points: Using a map or a scaled drawing to determine distances.
- Plane Table Surveys: Utilizing a plane table and alidade to record measurements and create a map.
- Triangulation: Calculating unknown distances based on a series of interconnected triangles.
Distance by Mechanical Devices
- Passometer: Counts steps taken by a person.
- Pedometer: Measures the distance walked by a person.
- Odometer: Measures distances traveled by a vehicle.
- Speedometer: Measures the speed and can be used to determine distances traveled.
- Perambulator: Automatically measures distance using a wheel and readings on a dial.
Distance by Photogrammetry
- Photogrammetry is the science of obtaining accurate measurements from photographs.
- It involves using aerial photographs taken from aircraft or satellites.
- Through analysis of the images, distances between points on the ground can be calculated.
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Description
Test your knowledge on the fundamental methods of measuring distance in surveying. This quiz covers various tools and techniques used in the field, including pacing, pedometers, and odometers. Perfect for students and professionals in engineering and surveying!
