Surveying-I Unit -1 PDF

SATHYABAMA INSTITUTE OF SCIENCE AND TECHNOLOGY DEPARTMENT OF Civil Engineering ` COURS...

SATHYABAMA INSTITUTE OF SCIENCE AND TECHNOLOGY DEPARTMENT OF Civil Engineering ` COURSE MATERIAL Subject Name: Surveying I Unit -I Subject Code:SCIA1303 Definition of Survey Surveying is the art of determining the relative positions of different objects on the surface of the earth by measuring the horizontal distances between them, and by preparing a map to any suitable scale. Thus, in this discipline, the measurements are taken only in the horizontal plane. Different methods and instruments are being used to facilitate the work of surveying. The primary aims of field surveying are:    To measure the Horizontal Distance between points.    To measure the Vertical elevation between points.   by measuring horizontal angles with To find out the Relative direction of lines reference to any arbitrary direction and   To find out Absolute direction by measuring horizontal angles with reference to a fixed direction. These parameters are utilized to find out the relative or absolute coordinates of a point / location. Objectives of Surveying    To collect field data;    To prepare plan or map of the area surveyed;    To analyze and to calculate the field parameters for setting out operation of actual engineering works.   To set out field parameters at the site for further engineering works. Division of Surveying The approximate shape of the earth can best be defined as an oblate tri-axial ovaloid. But, most of the civil engineering works, concern only with a small portion of  SATHYABAMA INSTITUTE OF SCIENCE AND TECHNOLOGY DEPARTMENT OF Civil Engineering ` COURSE MATERIAL Subject Name: Surveying I Unit -I Subject Code:SCIA1303 the earth which seems to be a plane surface. Thus, based upon the consideration of the shape of the earth, surveying is broadly divided into two types.    Geodetic Surveying   Plane Surveying Geodetic Surveying In this branch of surveying, the true shape of the earth is taken into consideration. This type of surveying is being carried out for highly precise work and is adopted for surveying of large area. Plane Surveying In this method of surveying, the mean surface of the earth is considered to be a plane surface. This type of survey is applicable for small area (less than 200 square kilometer). Thus for most of the Civil Engineering projects, methods of plane surveying are valid. This course is restricted to the different aspects of plane surveying. Henceforth, in this course work, the word surveying implies plane surveying. Classification of surveying Based on the purpose (for which surveying is being conducted), Surveying has been classified into:  Control surveying: To establish horizontal and vertical positions of control  points.   of land, also Land surveying: To determine the boundaries and areas of parcels  known as property survey, boundary survey or cadastral survey.  Topographic survey: To prepare a plan/ map of a region which includes natural  as well as and man-made features including elevation.  Engineering survey: To collect requisite data for planning, design and execution  of engineering projects. Three broad steps are 1) Reconnaissance survey: To explore site conditions and availability of infrastructures.  SATHYABAMA INSTITUTE OF SCIENCE AND TECHNOLOGY DEPARTMENT OF Civil Engineering ` COURSE MATERIAL Subject Name: Surveying I Unit -I Subject Code:SCIA1303 2) Preliminary survey: To collect adequate data to prepare plan / map of area to be used for planning and design. 3) Location survey: To set out work on the ground for actual construction / execution of the project.  Route survey: To plan, design, and laying out of route  such as highways,  railways, canals, pipelines, and other linear projects.  Construction surveys: Surveys which are required for establishment of points,  (after the plans have been lines, grades, and for staking out engineering works  prepared and the structural design has been done).  Astronomic surveys: To determine the latitude, longitude (of the observation station) and  azimuth (of a line through observation station) from astronomical  observation.  Mine surveys: Tocarry out surveying specific for opencast and underground mining purposes. Based on instruments:  Chain Surveying  Compass Surveying  Plane Table Surveying  Theodolite Surveying  Tachometric Surveying  Photographic Surveying Based on methods  Triangulation Surveying and,  Traverse Surveying  SATHYABAMA INSTITUTE OF SCIENCE AND TECHNOLOGY DEPARTMENT OF Civil Engineering ` COURSE MATERIAL Subject Name: Surveying I Unit -I Subject Code:SCIA1303 Triangulation Survey The selected survey stations are connected with survey lines in such a way resulting in the formation of network of triangles. This survey is useful in surveying larger areas with uneven site boundaries. The various formulas of the triangle are used to determine and area and various dimensions of the site. Transverse Survey The whole area is divided into various transverses for the easy surveying. Since this method involves division of survey area into various transverse, it is termed as Transverse Survey. Based on Object: 1. Geodetic Surveying 2. Mine Surveying 3. Archaeological Surveying, and 4. Military Surveying. Based on nature of field 1. Land Surveying 2. Marine Surveying and, 3. Astronomical Surveying Land Survey is further classified into following categories 1. Topographical Survey 2. Cadastral Survey 3. City Survey 4. Engineering Survey Land Survey This involved survey of objects in earth‟s surface.  SATHYABAMA INSTITUTE OF SCIENCE AND TECHNOLOGY DEPARTMENT OF Civil Engineering ` COURSE MATERIAL Subject Name: Surveying I Unit -I Subject Code:SCIA1303 Topographical Survey This survey is performed or determining the natural features of the country such as rivers, mountains, hills, valleys etc. and also artificial features such as canals, railways, roads, towns, villages etc. This helps to keep a record of existing natural features of the country. Cadastral Survey Cadastral Survey is similar to topographical survey. It only involves a little more precision and detailing in the process. Apart from determining the natural features, this method of survey also helps to determine boundaries of fields, houses and other properties. Cadastral Survey maps are drawn to a more larger scale as compared to topographical survey maps. This is performed in connection with town planning schemes such as drainage, water supply etc and for laying plots, roads, streets etc. City Survey City Survey is carried out in connection with various engineering works such as roads, railways etc and it also involves various works related to water supply sector such as reservoirs, wells etc. Engineering Survey Cadastral Survey is similar to topographical survey. It only involves a little more precision and detailing in the process. Apart from determining the natural features, this method of survey also helps to determine boundaries of fields, houses and other properties. Cadastral Survey maps are drawn to a more larger scale as compared to topographical survey maps. This is performed in connection with town planning schemes such as drainage, water supply etc and for laying plots, roads, streets etc.  SATHYABAMA INSTITUTE OF SCIENCE AND TECHNOLOGY DEPARTMENT OF Civil Engineering ` COURSE MATERIAL Subject Name: Surveying I Unit -I Subject Code:SCIA1303 Hydrographic or Marine Survey This involves survey of objects under water. Classification of Surveying Astronomical Survey This survey is conducted for the determining of latitudes, longitudes, azimuths, local time, etc. for various places on earth by observing heavenly bodies ( sun or the stars). Aerial Survey An aerial survey is conducted from aircraft. Aerial cameras take photographs of the surface of the earth in overlapping strips of land. This is also known as photographic survey. Aerial Survey Aerial survey is carried out by an aero plane in air. Astronomical Survey Principle of Surveying The fundamental principles upon which the surveying is being carried out are working from    To Work from the Whole to the Part and   To work from Part to the Whole Work from the Whole to the Part The whole area is enclosed by main station (Controlling Station) and main survey lines (Controlling lines). Then the area is divided into a number of parts by forming well conditioned triangles. The survey lines are measured very accurately by using tape or chain or any linear measurement equipments. Then the sides of the triangle measured. The purpose of working from whole to part is    To localize the errors and   To control the accumulation of errors.  SATHYABAMA INSTITUTE OF SCIENCE AND TECHNOLOGY DEPARTMENT OF Civil Engineering ` COURSE MATERIAL Subject Name: Surveying I Unit -I Subject Code:SCIA1303 This is being achieved by establishing a hierarchy of networks of control points. The less precise networks are established within the higher precise network and thus restrict the errors. To minimize the error limit, highest precise network (primary network) To locate a new station by at least two measurements (linear or angular) from fixed reference point The new stations should always be fixed by at least two measurements from fixed reference points. Linear and angular measurements are measured by using theodolite and prismatic compass. Thus the positions of main stations and direction of main survey lines are fixed. Operation in Surveying or characteristics of surveying Operation in Surveying consists of    Planning    Field Observation    Office Works   Setting out Works Planning To decide    The methods to be adopted for surveying;    The resources (instruments & personnel) to be used;   The control points / stations to be used (those already available and/ or to set up). The planning operation needs a-priori field visit and this is known as reconnaissance. Field Observation Field Observation involves    Collection of field data by making necessary measurements;   Recording of observed data in a systematic manner.  SATHYABAMA INSTITUTE OF SCIENCE AND TECHNOLOGY DEPARTMENT OF Civil Engineering ` COURSE MATERIAL Subject Name: Surveying I Unit -I Subject Code:SCIA1303 Before starting any field observation, the permanent adjustments of all the instruments need to be checked thoroughly by trained personnel and if required, it must be adjusted. Office Works Office Work involves    Processing, analyzing and calculation of observed data;    Preparation of necessary data (for making plan or map of the area);    Making of a plan or map of the area;  Computation  of relevant field parameters as per design for setting out engineering works at site. Setting out Works To locate and establish different parameters/ dimensions at the site as per design for further engineering works. Scales Representative Fraction The ratio of the distance on the drawing to the corresponding actual length of the object on the ground is known as the representative fractions. i.e.. Distance of the Object on Drawing R.F = Corresponding Actual distance of object on Ground Both the distances are in same unit. Scale is a fixed ratio that every distance on the plan bears with corresponding distance on the ground. Scale can be represented by the following method Representative Fraction For example 1, If a scale is 1 cm = 10 m  SATHYABAMA INSTITUTE OF SCIENCE AND TECHNOLOGY DEPARTMENT OF Civil Engineering ` COURSE MATERIAL Subject Name: Surveying I Unit -I Subject Code:SCIA1303 R.F. = 1 / 10 x 100 = 1 / 1000 or 1: 1000 For example 2, If a scale is 1 cm = 1000 m 0r 1 km R.F. = 1 / 1 x 1000 x 100 = 1 / 100000 or 1: 100000 This type of scale is called engineering scale. There are four main types of scales which are used for different purposes for measurements 1. Plain Scale 2. Diagonal Scale 3. Vernier Scale Plain Scale Plain Scale is one on which it is possible to measure two dimensions only. For example, measurements such as units and lengths, metres and decimetres etc.  SATHYABAMA INSTITUTE OF SCIENCE AND TECHNOLOGY DEPARTMENT OF Civil Engineering ` COURSE MATERIAL Subject Name: Surveying I Unit -I Subject Code:SCIA1303 Diagonal Scale On diagonal scale, it is possible to measure three dimensions such as metres, decimetres and centimetres, units , tens and hundreds; yards, feet and inches etc. A short length is divided into number of parts using the principle of similar triangle in which sides are proportional. 1-1 represent 1/10 PQ 2-2 represent 2/10 PQ 9-9 represent 9/10 PQ Vernier Scale A device used for measuring the fractional part of one of the smallest divisions of a graduated scale. It usually consists of a small auxiliary scale which slides alongside of the main scale. Least count of the vernier = the difference between smallest division on the main division and smallest division on the vernier scale.  SATHYABAMA INSTITUTE OF SCIENCE AND TECHNOLOGY DEPARTMENT OF Civil Engineering ` COURSE MATERIAL Subject Name: Surveying I Unit -I Subject Code:SCIA1303 Choice of Scale of a Map Scales are generally classified as large, medium and small as under. Large Scale: 1 cm= 10 m or less than 10 m Medium Scale: 1 cm = 10 m to 100 m Small Scale: 1 cm= 100 or more than 100 m Choice of Scale of a Map For most of engineering projects, the scale varies from 1 cm = 2.5 m to 100 m Small scale topographical maps are usually drawn to scale 1 cm = 1 km, a scale of 1 cm= 5 m to 50 m is generally used for plans prepared for subdivisions of land Choices of scale of a map  SATHYABAMA INSTITUTE OF SCIENCE AND TECHNOLOGY DEPARTMENT OF Civil Engineering ` COURSE MATERIAL Subject Name: Surveying I Unit -I Subject Code:SCIA1303 Conventional Signs  SATHYABAMA INSTITUTE OF SCIENCE AND TECHNOLOGY DEPARTMENT OF Civil Engineering ` COURSE MATERIAL Subject Name: Surveying I Unit -I Subject Code:SCIA1303  SATHYABAMA INSTITUTE OF SCIENCE AND TECHNOLOGY DEPARTMENT OF Civil Engineering ` COURSE MATERIAL Subject Name: Surveying I Unit -I Subject Code:SCIA1303 Methods of Linear Measurement The following methods are generally employed for the linear, measurement are as follows,  By Pacing or Stepping - The walking step of a man is considered as 2.5 Ft or 80 cm.  By Passometer - A small instrument just like a stop watch, The passometer is used for counting the number of steps automatically by some mechanical devices.  By speedometers - This is used for recording distances  By perambulator and, - It is a wheel fitted with a fork and handle. The wheel is graduated and shows a distance per revolution. There is a dial which records the number or revolutions.  By Chaining - This is an accurate method of measuring Distance. Accessories for Linear Measurements  Ranging Rods - Generally circular in section, of Diameter 25mm and length 2m.  Tapes - Cloth or linen tape, Metallic tape, Steel tape and Invar tape.  Arrows - Arrows made up of tempered steel wire of diameter 4 mm. One end of the arrow is bent into ring of Ø 50 mm and other end is pointed. Length 400 mm  ChainN - A Chain is prepared with 100 or 150 pieces of Galvanized mild steel wire of diameter 4mm. Two Brass handles are provided at the two ends of the chain.  SATHYABAMA INSTITUTE OF SCIENCE AND TECHNOLOGY DEPARTMENT OF Civil Engineering ` COURSE MATERIAL Subject Name: Surveying I Unit -I Subject Code:SCIA1303 Offset The lateral measurement taken from an object to the chain line is known as offset. Offset are taken to locate object with reference to the chain line. They may be of two kinds.    Perpendicular offset   Oblique offset  SATHYABAMA INSTITUTE OF SCIENCE AND TECHNOLOGY DEPARTMENT OF Civil Engineering ` COURSE MATERIAL Subject Name: Surveying I Unit -I Subject Code:SCIA1303 Perpendicular Offset When the lateral measurements are taken perpendicular to the chain line, they are called perpendicular offset. Perpendicular offset may be taken in the following ways, S.no Procedures Diagrams Building By setting a perpendicular by swinging the tape from the object 1 to the chain line. The point of the medium reading on the tape will be the base of the perpendicular. Object By setting a right angle in the ratio C 2 3:4:5 90 3m 5m A 4m B  SATHYABAMA INSTITUTE OF SCIENCE AND TECHNOLOGY DEPARTMENT OF Civil Engineering ` COURSE MATERIAL Subject Name: Surveying I Unit -I Subject Code:SCIA1303 Builder’s Squar By setting a right angle with help 3 of builder‟s square or tri-square 4 By setting a right angle by cross-staff or optical square Oblique Offset Any offset not perpendicular to the chain line is said to be oblique. Oblique offset are taken when the objects are at a long distance from the chain line or when it is not possible to set a right angle due to some difficulties such offset are taken in the following manner, Suppose AB is a chain line and P is the corner of a building. Two Points „a‟ and „b‟ are taken in the chain line. The chain ages of „a‟ and „b‟ are noted. The distances „ap‟ and „bp‟ are the oblique offset. When the triangle abp is plotted, the apex point p will represent the position of the corner of the building.  SATHYABAMA INSTITUTE OF SCIENCE AND TECHNOLOGY DEPARTMENT OF Civil Engineering ` COURSE MATERIAL Subject Name: Surveying I Unit -I Subject Code:SCIA1303 Perpendiculars offset are preferred for the following reasons,  They can be taken very quickly Building   The progress of survey is not hampered.  Oblique The entry in the field book is very easy Offset  The plotting of the offsets also becomes easy. P Number of offsets The offset should be taken according to the nature of the object. So, there is no A a b B hard and fast rule regarding the number of offsets. Some of the guidelines have to be followed while taking number of offsets,  When the boundary of the object is approximately parallel to the chain line, perpendicular offset are taken at regular intervals.  SATHYABAMA INSTITUTE OF SCIENCE AND TECHNOLOGY DEPARTMENT OF Civil Engineering ` COURSE MATERIAL Subject Name: Surveying I Unit -I Subject Code:SCIA1303 Boundary line Chain line    When the boundary is straight, perpendicular offsets are taken at both ends of it.     Wire Fencing Chain line  When the boundary is zigzag, perpendicular offset are taken at every point of bend to represent the shape of the boundary accurately. In such a case, the interval of the offsets may be irregular. Zigzag Boundary  SATHYABAMA INSTITUTE OF SCIENCE AND TECHNOLOGY DEPARTMENT OF Civil Engineering ` COURSE MATERIAL Subject Name: Surveying I Unit -I Subject Code:SCIA1303   the chain line perpendicularly, the chain age of the intersection point When a road crosses is to be noted. R O A a b D Chain line   When a road crosses a chain obliquely, the chain ages of intersection points „a‟ and „b‟ c R are noted. Then at least one offset is taken a O b on both sides of the intersection points. Chain line A More offsets may be taken depending on the D nature of the road. Here, perpendicular offsets are taken at „c‟ and„d‟.   and When the building is small, its corners are fixed by perpendicular or oblique offsets  the other dimensions are taken directly on the field and noted in the field book.   When the building is large. Zigzag in shape and oblique to the chain line, then the corners are fixed by perpendicular or oblique offsets. Then the full plan of the building is drawn on a 5m separate page along with the entire dimension. Building 1m 3m Chain line  SATHYABAMA INSTITUTE OF SCIENCE AND TECHNOLOGY DEPARTMENT OF Civil Engineering ` COURSE MATERIAL Subject Name: Surveying I Unit -I Subject Code:SCIA1303 Limiting length of offset The maximum length of the offset should not be more than the length of the tape used in the survey. Generally, the maximum length of the offset is limited to 15 m. however also depends upon the following factors.    The desired accuracy of the map    The scale of the map    The maximum allowable deflection of the offset from its true direction and,   The nature of the ground. Direct Measurements When the distance between points / stations are measured directly, usually by using tape, is known as direct method. Ranging: When the distance to be measured is more than a tape length, a straight line is required to be laid between the points/ stations along which measurements are to be carried out. The process of laying out a straight line between points is known as ranging. There are two types of Ranging 1. Direct Ranging 2. Indirect Ranging Direct Ranging When the end stations are inter visible, ranging is being carried out directly. The intermediate points are placed at distances having interval less than one tape length. Direct ranging  SATHYABAMA INSTITUTE OF SCIENCE AND TECHNOLOGY DEPARTMENT OF Civil Engineering ` COURSE MATERIAL Subject Name: Surveying I Unit -I Subject Code:SCIA1303 The intermediate points are found by moving a ranging pole in transverse direction and thus, points are selected in such as way that the end points and the intermediate points lie in a straight line (Figure) In this method, two flags, one ranging pole and a bunch of pegs are required in a team of at least one surveyor and one assistant. Indirect Ranging When the end stations between which a straight line is to be laid, are not inter visible, indirect method of ranging is being adopted. It is being carried out either by reciprocal method or by random line method. There are two types of Indirect Ranging 1. Reciprocal Ranging 2. Random Line Method Reciprocal Ranging Figure shows the field operations involved in reciprocal ranging. Let A and B are the two end points whose distance is required to be found and are not inter visible. To fix the intermediate points in a straight line between these points, two more points say C and Reciprocal Ranging  SATHYABAMA INSTITUTE OF SCIENCE AND TECHNOLOGY DEPARTMENT OF Civil Engineering ` COURSE MATERIAL Subject Name: Surveying I Unit -I Subject Code:SCIA1303 D are chosen in such a way that D & B are visible from C and C & A from D. Then, direct ranging is being carried out alternatively along DCA and CDB for a number of times so that ACDB lie in a straight line. Random Line Method In this method, (Figure) a random line such as BQ is being laid such that R is visible from Q. A perpendicular QR is being erected at Q and measure its distance. Then the desired distance BR is being calculated using distance formula. In laying the line BR, intermediate points are established first. These are laid by taking offset from the random line at distances calculated by using the method of similar triangle such as Ranging by Random Line Method After locating the intermediate points on the line BR, the obstructions get cleared to make the end points intervisible. Then, direct ranging is being carried out to obtain a extended continous straight line.