Fundamentals of Surveying

Fundamentals of Surveying

Contents

Define the term Surveying 2

Recall the Primary Division of Surveying 2

Classify Surveying on the basis of the following: i. Nature of Field Survey, ii. Object of Survey, iii. Instrument Used 3

Recall the Principle of Surveying 5

Locating new points by measurement of minimum two reference points 6

Define the following terms: i. Plan, ii. Map iii. Scale 8

List various Scales used in the Surveying 8

Describe Errors due to the wrong Scales 10

Recall The fieldwork of the Surveyor 11

Recall Office work of the Surveyor 12

Describe care and adjustment of the Instrument 13

Define the following Terms: i. Precision, ii. Accuracy, iii. Errors 14

Differentiate between Precision and Accuracy 15

List various types of Error 16

Recall different Sources of Errors 17

Define Probability Curve 18

Recall the following terms: i. Principle of Least Square, ii. Most Probable Value, iii. Most Probable Error 18

Describe Errors in the computed Results 19

Define the term Surveying

Surveying is a branch of engineering that deals with the determination of the relative position of points and physical and cultural features on or near the surface of the earth and the representation of that information on maps, plans, and sections. Surveying involves the use of mathematical, geometrical, and technological tools to collect, analyse, and present data about physical and cultural features. The goal of surveying is to provide accurate and precise information about the location, shape, and dimensions of these features, which can then be used for a wide range of purposes, including construction, mapping, land use planning, and environmental protection. Surveying is an essential discipline in many fields, including civil engineering, construction, geography, and land surveying, and it plays a critical role in ensuring that projects are completed safely, efficiently, and effectively.

Recall the Primary Division of Surveying

The primary division of surveying can be categorised into two main areas: Geodetic Surveying and Engineering Surveying.

  1. Geodetic Surveying: This type of surveying deals with the measurement of large distances and angles over the surface of the earth. It involves the use of complex mathematical models and sophisticated instrumentation to determine the exact location of points on the earth’s surface. Geodetic surveying is often used for mapping and boundary determination, as well as for the establishment of control points for other types of surveys.
  2. Engineering Surveying: This type of surveying deals with the measurement of smaller distances and angles for the purpose of construction and land development. It includes a wide range of activities, such as land and topographic surveying, construction layout, and as-built surveys. Engineering surveying is focused on providing the necessary information for the design, construction, and maintenance of infrastructure, buildings, and other structures.

These two types of surveying complement each other and are used in conjunction with each other to provide comprehensive information for various purposes. Geodetic surveying provides the framework for engineering surveying, while engineering surveying provides the detailed information necessary for construction and development.

Classify Surveying on the basis of the following: i. Nature of Field Survey, ii. Object of Survey, iii. Instrument Used

  1. Classifying Surveying based on the Nature of Field Survey:

i. Ground Surveying: This type of surveying involves taking measurements and observations on the ground, usually with hand-held instruments. Ground surveying is used for a variety of purposes, including boundary surveys, topographic surveys, and construction layout surveys.

ii. Aerial Surveying: This type of surveying involves the use of aerial platforms, such as aeroplanes, helicopters, or drones, to collect information about the earth’s surface. Aerial surveying is often used for large-scale mapping projects, for monitoring changes in land use, and for natural resource management.

  1. Classifying Surveying based on the Object of Survey:

i. Cadastral Surveying: This type of surveying is focused on the measurement and mapping of boundaries for the purpose of land ownership and property rights. Cadastral surveys are used for the creation of property deeds, the establishment of boundary markers, and the resolution of boundary disputes.

ii. Geodetic Surveying: This type of surveying deals with the measurement of large distances and angles over the surface of the earth. Geodetic surveying is used for mapping and boundary determination, as well as for the establishment of control points for other types of surveys.

iii. Topographic Surveying: This type of surveying focuses on the measurement and mapping of natural and cultural features on the earth’s surface, such as hills, valleys, rivers, and buildings. Topographic surveying is used for land use planning, natural resource management, and infrastructure development.

  1. Classifying Surveying based on the Instrument Used:

i. Traditional Surveying: This type of surveying involves the use of traditional survey instruments, such as chains, tapes, and levels, to collect data. Traditional surveying is still widely used, especially for smaller projects, and is often seen as a less expensive alternative to modern surveying methods.

ii. Modern Surveying: This type of surveying involves the use of advanced instrumentation, such as total stations, GPS receivers, and laser scanners, to collect data. Modern surveying is used for a wide range of purposes and is often seen as more efficient and accurate than traditional surveying methods.

Recall the Principle of Surveying

Surveying is a process of measuring and mapping the earth’s surface to determine its features, size, and position. The Principle of Surveying refers to a set of fundamental principles that guide the surveying process. Recall of these principles is essential for surveyors to ensure accuracy, precision, and reliability of their measurements.

The main principles of surveying are,

  • To work from whole to the part
  • Locating new points by measurement of minimum two reference points

Working from the whole to the part:

The main principle of this method is establishing the survey work from the whole to the part.

For example, if you are going to take surveys for vast land first, you have to fix systematic control points with high precision around the area—a boundary line formed by connecting the points which are the main skeleton drawing of the survey.

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The survey points are established by triangulation or traverse around the area. Then the triangles are broken into small areas and can be measured by less workmanship.

The primary purpose of work from the whole to the part survey is to avoid the error. In case the survey works are established by part to whole, then we have to face many mistakes in the surveying.

Locating new points by measurement of minimum two reference points

Two different independent processes have to be done to fix a new point. The two different methods can cross-check together.

From the above picture, C is new, which has to be fixed & point A, B are the given points.

  • Now the point C can be fixed by measuring the distance of AC & BC; it is one method of process.
  • A perpendicular line may be drawn from point C to baseline AB. Now we have got two different possibilities to locate point C by the line CD.

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For example, if you are going to take surveys for vast land first, you have to fix systematic control points with high precision around the area—a boundary line formed by connecting the points which are the main skeleton drawing of the survey.

Define the following terms: i. Plan, ii. Map iii. Scale

  1. Plan: A plan is a two-dimensional representation of a structure, building, or other object, usually drawn to scale, that provides an overhead view of the object’s layout and design. Plans are used to visualize and communicate the design of a structure, to aid in the construction process, and to provide a record of the design for future reference.
  2. Map: A map is a graphical representation of a geographical area that shows the location and distribution of physical and cultural features, such as rivers, mountains, roads, and buildings. Maps can be created in a variety of scales and projections, and may include information such as topography, land use, and political boundaries.
  3. Scale: Scale refers to the relationship between the size of a feature or object represented on a map or plan, and its actual size in the real world. The scale of a map or plan is typically expressed as a fraction or a ratio, such as 1:10,000, which means that 1 unit on the map represents 10,000 units in the real world. Scales can range from small, detailed maps that show individual buildings and structures, to large-scale maps that cover entire continents.

List various Scales used in the Surveying

Plane Scale :

It is possible to measure two successive dimensions only.

Diagonal Scale :

It is possible to measure three successive dimensions.

Chord scale :

It is used to set out angles without using a protractor.

Vernier Scale :

It is a device for accurately measuring the fractional part of the smallest division on a graduated scale. It divided into,

  • Direct Vernier : ‘n’ divisions on the vernier scale are equal in length to (n – 1) divisions on the main scale. Thus ‘n’ divisions of vernier = {n -1) of main scale :∴ n ‘v’ = (n-1) ‘s’ or v = {(n-1)/n}*s

Where, n = total No. of divisions on vernier scale, v = length of one division on the vernier, s = length of one division on the main scale. The least count (L.C) is, therefore given by

L.C = s – v.

L.C = s – {(n-1)/n}*s.

L.C = s/n.

  • Retrograde Vernier : ‘n’ divisions of the vernier scale are equal to ‘(n+1)’ divisions on the main scale. ∴ n ‘v’ = (n+1) ‘s’
  • Extended Vernier : ‘n’ divisions of the vernier scale are equal in length to (2n – 1) divisions of the main scale. Therefore,
    ∴ n ‘v’ = (2n-1)s
    ∴ v = {(2n-1)/n}s
  • Double Vernier : It is used when the graduations on the main scale are numbered in both directions. It is a combination of both direct and retrograde verniers.
  • Double folded vernier : Its length is half of corresponding double verniers – economy of space.

Describe Errors due to the wrong Scales

Errors can occur when the wrong scale is used in surveying or mapping. Some of the most common errors due to the wrong scales include:

  1. Over-representation: If a large-scale map is used for a small area, features may be over-represented, appearing larger on the map than they actually are in reality. This can lead to inaccuracies in measurements and a false sense of the size of features.
  2. Under-representation: If a small scale map is used for a large area, features may be under-represented, appearing smaller on the map than they actually are in reality. This can result in a lack of detail and an incomplete picture of the area being mapped.
  3. Misinterpretation: If a map or plan is drawn at a different scale than the original survey, features may appear differently and may be misinterpreted. This can lead to incorrect conclusions and decisions being made based on the map or plan.
  4. Inaccurate Measurements: If the wrong scale is used in surveying or mapping, measurements may be inaccurate. For example, if a large scale map is used to measure distances between two points, the measurements may be too small, and if a small scale map is used, the measurements may be too large.
  5. Misalignment: If a map or plan is drawn at a different scale than the original survey, features may not align correctly, leading to inaccuracies and incorrect information being presented.

To avoid these errors, it is important to use the correct scale for the type of information being represented and the level of detail required. In addition, it is important to accurately label the scale of the map or plan and to ensure that the scale is consistent throughout the map or plan.

Recall The fieldwork of the Surveyor

The fieldwork of the surveyor is the process of collecting data and measurements in the field to produce accurate and precise maps, plans, and other surveying products. The fieldwork of the surveyor typically involves the following steps:

  1. Planning: Before starting the fieldwork, the surveyor will plan the survey, taking into consideration the type of survey, the location, and the required accuracy. The surveyor will also determine the type of equipment needed, such as total stations, theodolites, or GPS receivers.
  2. Setting up the Equipment: Once on-site, the surveyor will set up the equipment, making sure that it is level, stable, and correctly aligned. The surveyor will also check the equipment to make sure that it is functioning correctly.
  3. Measuring and Recording Data: The surveyor will then start collecting data by measuring and recording the position of points and features in the field. This data is used to create maps, plans, and other surveying products.
  4. Verifying Measurements: To ensure the accuracy of the measurements, the surveyor will verify and check the data, making sure that it meets the required standards and specifications.
  5. Storing and Analysing Data: After collecting the data, the surveyor will store it, either on the surveying equipment or on a computer, where it can be analysed and processed.
  6. Producing Maps and Plans: The surveyor will then use the data collected in the field to produce accurate and detailed maps, plans, and other surveying products, such as cross-sections, profiles, and contour lines.

The fieldwork of the surveyor is a critical step in the surveying process and requires a high level of skill, knowledge, and precision. It is essential for the surveyor to have a thorough understanding of the equipment, techniques, and processes used in the field in order to produce accurate and reliable results.

Recall Office work of the Surveyor

The office work of the surveyor is the process of analysing and processing the data collected in the field to produce accurate and detailed maps, plans, and other surveying products. The office work of the surveyor typically involves the following steps:

  1. Data Processing: The surveyor will process the data collected in the field, adjusting and correcting any errors or inconsistencies. The surveyor will also convert the raw data into a format that can be used to produce maps and plans.
  2. Analysing Data: The surveyor will analyse the processed data to identify any trends, patterns, or anomalies. This information is used to refine and improve the accuracy of the maps and plans produced.
  3. Drafting Maps and Plans: Using the processed and analysed data, the surveyor will draft accurate and detailed maps and plans. The surveyor will also use specialised software, such as GIS or CAD, to create and edit the maps and plans.
  4. Checking and Verifying Maps and Plans: The surveyor will check and verify the maps and plans produced, making sure that they are accurate and meet the required standards and specifications.
  5. Presenting Maps and Plans: The surveyor will present the maps and plans produced to the client or other stakeholders, providing explanations and interpretations of the data and the results.
  6. Storing and Archiving Data: The surveyor will store and archive the data and maps and plans produced, making sure that they are properly labelled, organised, and accessible for future reference.

The office work of the surveyor is a critical step in the surveying process and requires a high level of skill, knowledge, and attention to detail. It is essential for the surveyor to have a thorough understanding of the software and tools used in the office, as well as the techniques and processes used to analyze and process the data collected in the field.

Describe care and adjustment of the Instrument

The care and adjustment of surveying instruments are critical steps in ensuring accurate and reliable results in surveying. Proper care and adjustment of surveying instruments can prevent errors and damage to the instruments, and help to ensure accurate and precise measurements. The following are some of the key steps involved in the care and adjustment of surveying instruments:

  1. Cleaning: The first step in caring for surveying instruments is to clean them regularly. Dirt and debris can accumulate on the lenses and mirrors, affecting the accuracy of the readings. The instruments should be cleaned using a soft, clean cloth, and a cleaning solution if necessary.
  2. Storing: When not in use, surveying instruments should be stored in a clean and dry place. Exposure to moisture and extreme temperatures can cause damage to the instruments and affect their accuracy. The instruments should be stored in their original cases or in a padded bag to protect them from damage.
  3. Maintenance: Regular maintenance is important to ensure that the instruments are in good working order. This may include calibrating the instruments, adjusting the level, and tightening loose screws and bolts.
  4. Calibration: Calibration is the process of adjusting the instruments to ensure that they are reading accurately. Calibration should be done regularly and after any major maintenance or repairs to the instruments. The calibration process may involve adjusting the level, the vertical and horizontal angles, and the sighting mechanism.
  5. Checking the Level: The level is a critical component of surveying instruments and must be checked regularly to ensure that it is accurate. The level should be checked using a spirit level, and adjustments should be made as necessary to ensure that it is reading accurately.
  6. Adjusting the Vertical and Horizontal Angles: The vertical and horizontal angles of surveying instruments must also be adjusted regularly to ensure accurate readings. Adjustments should be made using a plumb bob or a spirit level, and any loose screws or bolts should be tightened.
  7. Replacing Damaged Parts: If any parts of the surveying instruments are damaged, they should be replaced as soon as possible. Damaged parts can affect the accuracy of the readings and can cause further damage to the instruments if not addressed.

Proper care and adjustment of surveying instruments are essential for ensuring accurate and reliable results in surveying. The surveyor should be knowledgeable about the instruments being used, and should follow the manufacturer’s recommendations for care and adjustment.

Define the following Terms: i. Precision, ii. Accuracy, iii. Errors

  1. Precision: Precision refers to the degree of consistency and repeatability of a set of measurements. It is a measure of how close the individual measurements are to each other, regardless of whether they are close to the true value.
  2. Accuracy: Accuracy refers to the degree of closeness of a measurement to its true value. It is a measure of how close the measurement is to the actual, true value of the quantity being measured.
  3. Errors: Errors are deviations of a measurement from the true value of the quantity being measured. Errors can occur due to a variety of factors, including incorrect instrument readings, incorrect use of the instrument, incorrect data recording, and human error.

Errors can be systematic or random. Systematic errors are consistent and repeatable, and they affect all measurements in the same way. Systematic errors can be caused by factors such as incorrect instrument calibration, incorrect use of the instrument, or incorrect data recording. Random errors, on the other hand, are unpredictable and vary from measurement to measurement. Random errors can be caused by factors such as environmental conditions, human error, or instrument noise.

Precision and accuracy are important concepts in surveying because they affect the reliability of the data collected. Precise measurements are not necessarily accurate, and accurate measurements are not necessarily precise. The goal of surveying is to achieve both precision and accuracy in order to produce reliable and trustworthy data.

Differentiate between Precision and Accuracy

Precision and accuracy are two important concepts in surveying and are often confused with each other. However, they refer to different aspects of measurement.

  1. Precision refers to the degree of consistency and repeatability of a set of measurements. It is a measure of how close the individual measurements are to each other, regardless of whether they are close to the true value. For example, if you measure the same object multiple times and get similar results, then the measurements are said to be precise.
  2. Accuracy, on the other hand, refers to the degree of closeness of a measurement to its true value. It is a measure of how close the measurement is to the actual, true value of the quantity being measured. For example, if you measure the length of an object with a ruler and the result is close to the actual length, then the measurement is said to be accurate.

It is possible to have precise measurements that are not accurate and vice versa. For example, if you measure the length of an object with a ruler that has been stretched, you may get consistent results, but they will not be accurate because the ruler is not measuring the true length of the object. On the other hand, if you use a ruler that is not stretched, but you measure the length of the object while it is moving, you may get an accurate result, but it will not be precise because each measurement will be different.

In surveying, it is important to strive for both precision and accuracy in order to produce reliable and trustworthy data.

List various types of Error

Errors are a common occurrence in surveying and can be classified into several types, including:

  1. Instrumental errors: These are errors that arise from the use of surveying instruments, such as instruments that are not calibrated correctly or that have a malfunction.
  2. Human errors: These are errors that are made by the surveyor, such as measuring the wrong location, misreading the instrument, or making mathematical errors.
  3. Environmental errors: These are errors that arise from the conditions under which the survey is conducted, such as atmospheric conditions that affect the line of sight or temperature changes that cause expansion or contraction of the instruments.
  4. Natural errors: These are errors that are due to natural causes, such as changes in the terrain or the movement of objects, such as trees or buildings, that obstruct the line of sight.
  5. Systematic errors: These are errors that are inherent in the surveying system and affect all measurements in the same way. For example, a systematic error might occur if the instrument is not level, causing all measurements to be slightly off.
  6. Random errors: These are errors that are unpredictable and occur randomly. They may be due to measurement variations caused by wind, vibration, or other factors that cannot be controlled.

It is important to be aware of the different types of errors in surveying and to implement procedures to minimise them. This can include regularly calibrating the instruments, conducting surveys under controlled conditions, and double-checking measurements to ensure accuracy.

Recall different Sources of Errors

Errors in surveying can arise from several sources, including:

  1. Instrumental errors: These are errors that arise from the use of surveying instruments, such as instruments that are not calibrated correctly or that have a malfunction.
  2. Human errors: These are errors that are made by the surveyor, such as measuring the wrong location, misreading the instrument, or making mathematical errors.
  3. Environmental errors: These are errors that arise from the conditions under which the survey is conducted, such as atmospheric conditions that affect the line of sight or temperature changes that cause expansion or contraction of the instruments.
  4. Natural errors: These are errors that are due to natural causes, such as changes in the terrain or the movement of objects, such as trees or buildings, that obstruct the line of sight.
  5. Systematic errors: These are errors that are inherent in the surveying system and affect all measurements in the same way. For example, a systematic error might occur if the instrument is not level, causing all measurements to be slightly off.
  6. Random errors: These are errors that are unpredictable and occur randomly. They may be due to measurement variations caused by wind, vibration, or other factors that cannot be controlled.

It is important to be aware of the different sources of errors in surveying and to implement procedures to minimise them. This can include regularly calibrating the instruments, conducting surveys under controlled conditions, and double-checking measurements to ensure accuracy.

Define Probability Curve

A probability curve is a graphical representation of the distribution of a set of data points. It is used to describe the likelihood of a particular value occurring within a set of data. The curve is usually represented as a smooth curve that is symmetrical about the mean of the data set.

The most commonly used probability curve is the normal distribution, also known as the Gaussian distribution. This curve is used to describe the distribution of continuous variables, such as height, weight, and intelligence, that tend to cluster around the mean and have a bell-shaped distribution.

The probability curve can be used to calculate probabilities, such as the probability of obtaining a certain measurement within a certain range. This information is useful in many applications, including quality control, risk management, and decision making.

In surveying, the probability curve is used to describe the distribution of measurement errors and to estimate the likelihood of obtaining a certain level of precision and accuracy. This information is useful in determining the required number of measurements, the accuracy of the instruments, and the minimum acceptable level of error for a particular survey.

Recall the following terms: i. Principle of Least Square, ii. Most Probable Value, iii. Most Probable Error

  1. Principle of Least Squares: The principle of least squares is a mathematical method used to fit a curve to a set of data points. It is based on the idea that the best fit curve is one that minimises the sum of the squares of the differences between the observed data points and the values predicted by the curve.
  2. Most Probable Value: The most probable value is the value of a variable that is most likely to occur based on a set of data. It is often used as an estimate of the true value of a variable and is calculated as the mean or median of a set of data.
  3. Most Probable Error: The most probable error is a measure of the uncertainty associated with a measurement. It is calculated as the standard deviation of a set of measurements and represents the range within which the true value of a variable is most likely to lie.

In surveying, the principle of least squares is used to analyse the measurement errors and to calculate the most probable value of a particular variable. This information is useful in determining the precision and accuracy of the measurements and in correcting for systematic errors.

The most probable error is used to determine the level of uncertainty associated with a particular measurement and to estimate the confidence interval within which the true value of a variable is most likely to lie. This information is useful in determining the minimum acceptable level of error for a particular survey and in making decisions about the use of the data.

Describe Errors in the computed Results

Errors in computed results refer to inaccuracies or deviations in the final results obtained from a survey. These errors can arise from a variety of sources, including:

  1. Measurement Errors: Measurement errors are errors that occur during the process of taking readings or measurements. These errors can be caused by incorrect instrument readings, mis-measurements, or errors in the calculation of the readings.
  2. Instrumental Errors: Instrumental errors refer to errors that are inherent in the instruments used for taking measurements. These errors can be caused by factors such as manufacturing tolerances, instrument wear and tear, or environmental conditions.
  3. Human Errors: Human errors refer to errors that are made by the surveyor or other individuals involved in the survey process. These errors can be caused by incorrect data entry, incorrect calculations, or miscommunication between team members.
  4. Environmental Errors: Environmental errors refer to errors that are caused by external factors such as weather conditions, changes in temperature, or changes in atmospheric pressure.
  5. Systematic Errors: Systematic errors refer to errors that are consistent and occur in the same direction for every measurement. These errors can be caused by incorrect instrument settings or incorrect reference data.

In surveying, it is important to minimise errors in the computed results in order to ensure that the survey data is accurate and reliable. This is achieved by using appropriate techniques for measuring and analysing the data, such as the principle of least squares and the calculation of the most probable error. Additionally, it is important to use high-quality instruments and to train surveyors to use them correctly, in order to minimise the impact of instrumental and human errors.