Chapter 1


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Chapter 1

  1. 1. `BASIC SURVEYING NOTES CH# 1 SURVEYING Q1. Ans. What does surveying means? What is the purpose of surveying? Survey Collecting different type of information about something is called survey. Surveying In civil engineering, survey means to collect necessary information about a region and represent that information in the form of drawing, and the process is called surveying. Purpose of surveying     Q2. Ans. The basic purpose of survey is to get necessary information about an area. To prepare a plan in the form of a map. To represent area in the form of horizontal lines. To represent vertical distances in the form of contour lines. How surveying is classified? There are two basic types of surveying. 1) Geodetic survey. 2) Plane survey. Geodetic survey Survey in which curvature of earth is taken in account is called geodetic survey. The surface of earth is considered curved in geodetic survey. This type of survey is used for surveying on large scale. The government organizations mostly use this type of survey i.e. survey of Pakistan do this type of survey. Plane survey The survey in which curvature of earth is not taken in account is called plane survey. The surface of earth is considered flat in plane survey. This survey is mostly carried out for small areas. The correctiveness of this survey is less as compared to geodetic survey. In this survey the length is not taken greater than 15k.m and 260k.m2 area. Q3. Ans. Write down the basic principles of surveying? Basic principles of surveying are as follows. First principle  First of all survey is done for large area and then for small area. This principle is called whole to part. Second principle  For finding the position of any relative point during survey at least two measurements will be taken, i.e. i. Measurement of both the lines. ii. Measurement of both the angles. iii. Measurement of a line and an angle. Q4. State the instruments for taking linear and angular measurements. Instruments for taking linear measurement The following instruments are used taking linear measurements. Written By: Aadil Furqan Kundi Page 1
  2. 2. `BASIC SURVEYING NOTES        Pedometer Chain Steel Band Tape Tachometer Distance Meter Total Station Instruments for taking angular measurements The following instruments are used for taking angular measurements.  `Compass  Clinometer  Sextant  Theodolite  Total Station. Q5. Ans. Define chain surveying? State the principles of chain surveying. Chain surveying Type of survey in which we use chain for taking the measurements, on the basis of instrument used it is termed as chain survey. Chain survey is an ancient method of surveying which has not too much correctness. This survey is usually used for the less importance projects. In this survey chain is used to measure the lengths of the lines. Principles of chain surveying        Q6. Ans. Divide the area to be surveyed into number of triangles. Lines should run through the level ground. Offset should be short as possible. The sides and area are directly measured in the field. No angular measurements are taken. There should be one base line in a survey upon which surveyor forms the triangles. Stations should be visible. Enlist the advantages and disadvantages of chain survey. Advantages of chain survey Advantages of chain survey are as follows.  It is a simple way of carrying out survey.  The instruments used in chain survey are simple and cheap.  It does not require a highly educated surveyor. Little educated but experienced surveyors can carry out chain survey easily.  It is more suitable in small and level areas. Disadvantages of chain survey Chain survey has the following disadvantages.  This method is not suitable for hilly areas.  It is costly and time consuming if it is carried out for large scale survey.  This survey is not suitable for populated area because forming triangles there are difficult.  It is not a becoming way for survey of roads, railway lines and streams etc. Written By: Aadil Furqan Kundi Page 2
  3. 3. `BASIC SURVEYING NOTES Q7. Write short notes on the following. 1) Base line 2) Tie line 3) Check line 4) Offset Base line This line is the basic line of chain survey. This line is passed through the centre of the area. For passing the base line flat surface is selected. The correctness of survey depends on the base line. In chain survey first of all base line is measured and then other lines. Tie line During carrying out chain survey a surveyor attempts that no area remains without details. Some times a small area remains in the large lines and the area is greater than tape and that is why an extra line is passed to know the details which are called tie line. Check line Check lines are also called proof lines. The lines drawn for representing the other chain lines in chain survey map correctly and checking the details obtained from other check lines. This line connects a station with other chain lines. Offset line For measuring the points near the chain lines, the lines drawn to the relative points are called offset lines. Offset lines are of two types. 1) Right offset 2) Oblique offset Right offset This offset is taken perpendicularly to the chain line. Offset taken at that point of chain line, the length of that point is called reduced distance (R.D). Oblique offset The points located near the chain line, the lines connecting these points with the chain line at other than right angle are called oblique offset. For representing any one point at least two oblique offsets are taken. Q8. Ans. What are the main types of ranging? Ranging Before measuring the line, the line is possibly directed on the ground with help of ranging rod. This process of directing is called ranging. OR The process of making number of intermediate points straight on the survey line joining two stations in the field so that the length between them may be measured correctly. Types of ranging The chain line is ranged in two ways. 1) Direct ranging 2) Indirect ranging Direct ranging This method is used that time when both the borders of line are clearly seen and the surface of earth is flat. For ranging the line the ranging rods are arranged at both the ends of the survey line. Before arranging the ranging rods the stations are foreordained with the help of pegs. Ranging rods are just arranged behind the pegs and then more rods are arranged. Indirect ranging Written By: Aadil Furqan Kundi Page 3
  4. 4. `BASIC SURVEYING NOTES This method of ranging is adopted that time when there is any slope or cliff between the ends of the line. This method is also adopted that time when the length of the line is too long that the ranging rods at the ends of the line can not be seen conjunctively. This method is also called reciprocal ranging. IMPORTANT TERMS Engineering survey Survey which is carried out for the determination and estimation of quantities for designing engineering works such as roads, building, bridges etc. Military survey This survey is carried out for fixing points of strategic importance for armed force purposes. Mine survey The survey carried out for excavation in earth for getting out metals and mineral wealth such as coal, gypsum, gold etc. Geological survey The survey carried out to find out about the earth’s surface is called geological survey. Division based upon field of surveying Land survey 1) Topographical survey The survey carried out for ascertaining description of features of geographical area such as township, railways, roads etc. 2) Cadastral survey The surveys carried out for fixing the property lines, calculation of areas of landed properties, preparation of revenue maps of states are called cadastral surveys. This survey is generally plotted to a larger scale than the topographic survey. 3) City survey The survey carried out for laying out plots and construction of plumbing, drainage works etc. Marine survey The survey carried out for the determining level of water, depth of water, mean sea level, navigation, harbor works, and discharge of water from the sea is called marine survey. Astronomical survey The survey carried out for determining well and absolute location of different places and direction of any line on the surface of earth by making observation with heavenly bodies i.e. sun and stars is called astronomical survey. Geographic information system Geographic information system is such a system in which the data obtained from survey is saved, processed and maps are prepared. It is briefly known as G.I.S. the data may be obtained from the total station and global positioning system devices etc. Method of chain survey For doing the chain survey of an area the following the following are steps are taken. 1. Reconnaissance 2. Preparation of index plan Written By: Aadil Furqan Kundi Page 4
  5. 5. `BASIC SURVEYING NOTES 1. 2. 3. 4. 5. 6. 3. Selection of station points 4. Selection of base line 5. Chaining 6. Drawing work Reconnaissance: - the area for which survey is to be done is checked and looked to its prominent details like tracks, drainage, sewerage system, populated area, railway track and roads etc. this step of looking into the general details of an area is called reconnaissance. Preparation of index plan: - index plan is also called “key plan”. After doing the reconnaissance rough sketch of the complete area is prepared. The general details of the area are shown in this sketch. This sketch is called index plan. Selection of station points: - after doing the reconnaissance and preparation of index plan, station points are selected on the ground. During selecting the station points, it is kept in mind that two stations must be at certain distance that they are visible to each other and their should be no obstacle between them. Selection of base line: - after the selection of station points, the base line is passed through the center of the area. During the selection of base line it is attempted that no point should be away from the base line so that all the important details can be checked out. The correctness of survey of an area depends upon this line. Chaining: - in this step the base line and other lines are measured and the details of the points around the base are noted. In this step first of all base line is measured and then other lines. Drawing work:- after the completion of field work, all the details of the area are represented on the map. Before making the drawing, the area surveyed is pondered over and is attempted that no details may remain in showing the map. First of all a suitable scale is selected and then sketch is prepared. All the details are shown by specific symbols. Written By: Aadil Furqan Kundi Page 5