Introduction to Surveying PDF

Introduction to Surveying At the end of the lesson, the student must be able to: 1. Define surveying. 2. Differentiate plane to Geodetic Surveying. 3. Know the development of surveying instruments & surveying measurements. “Surveying is the art of determining the positions of points on or near t...

Introduction to Surveying At the end of the lesson, the student must be able to: 1. Define surveying. 2. Differentiate plane to Geodetic Surveying. 3. Know the development of surveying instruments & surveying measurements. “Surveying is the art of determining the positions of points on or near the earth’s surface by means of measurement in the three elements of space; namely, distance, direction, and elevation.” – Rayner and Schmidt “Surveying is the art of measuring horizontal and vertical distances between objects, of measuring angles between lines, of determining the direction of lines, and of establishing points by predetermined angular and linear measurements.” – Davis, Foote, Anderson, and Mikhail. Surveys are divided into two general classifications, plane and geodetic. 1. Plane Surveying – is the type of surveying in which the earth is considered to be a flat surface, and where distances and areas involved are of limited extent that the exact shape of the earth is disregarded. 2. Geodetic Surveying – are surveys of wide extent which take into account the spheroidal shape of the earth. Development of Surveying Instruments  Surveying instruments were developed gradually. It is believed that, an extensive use of surveying instruments came about during the early days of the Roman Empire. This remarkable engineering ability of Romans is clearly demonstrated by their extensive construction of structures and buildings which continue to exist even up to this modern era. The following instruments were the early forerunners of our present-day surveying instruments. 1. Astrolabe. The astrolabe of Hipparchus is considered to be one of the best known of the measuring instruments that have come down from ancient times. It was developed sometime in 140 B.C., and further improved by Ptolemy. The instrument had a metal circle with a pointer hinged at its center and held by a ring at the top, and a cross staff, a wooden rod about 1.25 meters long with an adjustable cross arm at right angles to it. The known length of the arms of the cross staff allow distances and angles to be determined by proportion. It was originally designed for determining the altitude of stars. 2. Telescope. The invention of the telescope in. 1607 is generally accredited to Lippershey. In 1609, Galileo constructed a refracting telescope for astronomical observations. However, it was only when cross hairs for fixing the line of sight were introduced, that the telescope was fixed in early surveying instruments. 3. Early Transit. The invention of the transit is credited to Young and Draper who worked independently from each other sometime in 1830. Both men were able to put together in one instrument the essential parts of what has long been known as the universal surveying instrument. 4. Semicircumferentor. An early surveying instrument which was used to measure and lay off angles, and establish lines of sight by employing peep sights. 5. Plane Table. One of the oldest types of surveying instruments used in field mapping. It consists of a board attached to a tripod in such a way that it can be leveled or rotated to any desired direction. 6. Dioptra. The dioptra, which was perfected by Heron of Alexandria, was used in leveling and for measuring horizontal and vertical angles. It consists es- sentially of a copper tube supported on a standard and could be rotated in either a horizontal or vertical plane. For measuring horizontal angles, a flat circular disc with graduations in degrees is used. An arm containing sighting apertures at either end could be rotated to any desired position on the disc. 7. Roman Groma. The Roman surveyors used the groma instrument for aligning· or sighting as an points. It consisted basically of cross arms fixed at right angles and pivoted eccentrically upon a vertical staff. Plumb lines were suspended from the ends of the arms. By employing the groma two lines at right angles to each other could be established on the ground where it is set up. 8. Libella. The Assyrians and Egyptians are believed to be the first users of the libella.The instrument had an A-frame with a plumb line suspended from its apex and was used to' determine the horizontal. Archeologists are of the belief that the horizontal foundations of the great pyramids of Egypt were probably defined by this device. 9. Vernier. The vernier is a short auxiliary scale placed alongside the graduated scale of an instrument, by means of which fractional parts of the smallest or least division of the main scale can be determined precisely without having to interpolate. It was invented in 1631 by a Frenchman name Pierre Vernier. Surveying instruments employ either a direct or retrograde vernier 10. Diopter. An instrument developed by the Greeks sometime in 130 B.C., and known to be their most famous surveying instrument. The diopter was used for leveling, laying off right angles, and for measuring horizontal and vertical angles. Since the telescope was not yet invented during the time the diopter was used, peep sights were employed for sighting and in aligning the device. 11. Compass. The magnetic compass came into wide use during the 13th century for determining the direction of lines and in calculating angles between lines. It was first introduced for use in navigation. The compass consists of a magnetized steel needle mounted on a pivot at the center of a graduated circle. The needle continues to point toward magnetic north and gives a reading which is dependent upon the position of the graduated circle. 12. Gunter’s Chain. The Gunter's chain, which was invented by Sir Edmund Gunter in 1620, was the forerunner of instruments dsed for taping distances. It is 66 ft long and contains 100 links, so that distances may be recorded in chains and in decimal parts of the chain. Each part, called a link, is 0.66 ft or 7.92 inches long. 13. Chorobates. This instrument was designed for leveling work. It consisted of a horizontal straight-edge about 6 meters long with supporting legs, and a groove 2.5 cm deep and, 1.5m long on top. Water is poured into the groove and when the bar is leveled so that water stood evenly in the groove without spilling, a horizontal line is established. 14. Merchet. The merchet was a device for measuring time and meridian. It was first used by the Chaldeans in about 4,000 B.C. It consisted of a slotted palm leaf through which to sight and a bracket from which a plumb bob was suspended. -By sighting through the 'slot and past the plumb bob string, a straight line could be projected. Surveying Measurements Measurement is the process of determining the extent, size or dimensions of a particular quantity in comparison to a given standard. In surveying, measurements may be directly or indirectly. 1. Direct Measurements is a comparison of the measured quantity with a standard measuring unit or units employed for measuring quantity of that kind. 2. Indirect Measurements. When it is not possible to apply a measuring instrument directly to a quantity to be measured an indirect measurement is made. Units of Measurement 1. Linear, Area, and Volume Measurements. Using the prefixes, the following linear units are derived. 1 kilometer (km) = 1000 meters 1 meter (m) = 1000 millimeters 1 millimeter (mm) = 1000 micrometers 1 micrometer (𝜇𝑚) = 1000 millimicrometers 1 millimicrometers (m𝜇) = 1000 million micrometers 1 meter (m) = 10 decimeters 1 decimeter (dm) = 10 centimeters 1 centimeter (cm) = 10 millimeters 2. Angular Measurements. The SI unit for plane angle is the radian. The radian is defined as an angle subtended by an arc of a circle having a length equal to the radius of the circle. 2𝜋 rad = 360 deg 1 rad = 57 deg a. Sexagesimal units are the degree, minute, and second. The unit of angle used in surveying is the degree which is defined as 1/360th of a circle. 1 degree = 60 minutes 1 minute = 60 seconds Divisions of seconds are given in tenths, hundredths, and thousandths. 0 degrees ‘ minutes ‘’ seconds The primary unit of angular measurement in the metric system is the radian. A radian is defined as the angle between radius lines from either end of an arc of radius length. The use of radians and the value of 57.29578° will be mentioned again when dealing with circular and spiral curves. Another unit is the grad or gon. A grad is defined as 1/400 of a circle. The grad is widely used in much of the world as part of the metric system, even though the radian is the primary unit. Convert the following angles to decimal degrees and angles to degrees-minutes-seconds. b. Centesimal units. In this system the circumference of a circle (360 deg) is divided into 400 grads. The grad is divided into 100 centesimal minutes or 0.90 degree, and the minute is subdivided into 100 centesimal seconds or deg 00 min 32.4 sec. Grads are usually expressed in decimals. For example, 194g 45c 82cc  Significant Figures Some general rules regarding significant figures are: Rule 1 – Zeroes between other significant figures are significant, as, for example in the following values each of which contains 4 significant figures: 12.03, 35.06, and 4009. Rule 2 – For values less than one, zeroes immediately to the right of the decimal are not significant. They merely show the position of the decimal such as in the following values which contain three figures: 0.00325, 0.000468, and 0.0230. Rule 3 – Zeroes placed at the end of decimal numbers are significant such as: 169.30, 366.00, and 11.000. These three values all have significant figures.  Rounding Off Numbers Rounding off a value is the process of dropping one or more of the final digits so that the value contains only the significant figures required for further computation or for portraying the final results. The following procedures of rounding off values are generally accepted: 1. Digit is less than 5. When the digit to be dropped is less than 5, the number is written without the digit. Thus, 24.244, rounded off to the nearest hundredths, becomes 24.24 24.24, rounded off to the nearest tenths, the value becomes 24.2 2. Digit is equal to 5. When the digit to be dropped exactly 5, the nearest even number is used for the preceding digit. Thus 26.175, rounded off to the nearest hundredth become 26.18 156.285 would be 156.28 3. Digit is greater than 5. When the digit to be dropped is greater than 5, the number is written with the preceding digit increased by one. Thus, 226.276, rounded off to the nearest hundredth becomes 226.28 226.28 rounded off to the nearest tenths would be 226.3 Seatwork: 1. Convert the angles of a triangle to radians and show a computational check: (a) 91°30′16″ (b) 48°47′50″ 2. Convert 63.4550 to Degrees-Minutes-Seconds Surveying Field Notes Surveying field notes constitute the only reliable and permanent record of actual work in the field. Notes must be complete, legible, concise and comprehensive, and logically arranged according to recognized practice. Types of Notes The following are the five common types of notes kept in practice. 1. Sketches. A good sketch will help to convey a correct impression. Sketches are rarely made to exact scale, but in most cases they are made approximately to scale. They are drawn freehand and of liberal size. 2. Tabulations. A series of numerical values observed in the field are best shown in a tabulated format. Tabulated form of note keeping conveys the required information in a simple and definite manner. 3. Explanatory Notes. Explanatory notes provide a written description of what has been done in the field. These are employed to make clear what the numerical data and sketches fail to do. 4. Computations. Calculations or one kind and another form a large part of the work of surveying. Most surveying-type computations are made algebraically by the use of simple arithmetical steps and trigonometric functions. In some instances, graphical solutions using accurately scaled drawings are used. 5. Combination of the Above. The practice used in most extensive surveys is a combination of the above types of notes. The surveyor should be able to determine for himself which type of combination would be most logical to use in portraying the type of data gathered in the field. Information Found in Field Notebooks 1. Title of the Field Work or Name of Project. The official name of the project or title of the field work should always be identified. The location of the survey and preferably its nature or purpose should always be stated. 2. Time of Day and Date. These entries are necessary to document the notes and furnish a timetable, as well as correlate different surveys. 3. Weather Conditions. Temperature, wind velocity, typhoons, storms, and other weather conditions, such as fog, sunshine, and rain have a decided effect upon accuracy in surveying operations. 4. Names of Group Members and their Designation. The chief of party, instrumentman, tapeman, an other members of the survey party must be identified. This information will be necessary for documentation purposes and other future reference. From this information, duties and responsibilities can easily be pinpointed among the survey party members. 5. List of Equipment. All survey equipment used must be listed, including its make, brand, and serial number. The type of instrument used, and its adjustment, all have a definite effect on the accuracy of a survey. Proper identification of the particular equipment used in isolating errors in some cases. The Field Survey Party The following is a list of persons who may compose a field survey party. 1. Chief of Party – the person who is responsible for the overall direction, supervision, and operational logistical and technical requirements, and problems of a field survey operation. Prior to the execution of a survey project, he consults or confers with superiors regarding the project to be undertaken. - he is responsible for submitting survey reports and records, and sees to it that these are complete, accurate and adheres to prescribed technical standards and specifications.  - He prepares cost estimates of survey projects, and receives and disburses all cash expenses of the survey party. - He may be called upon to act as an expert witness in court on matters relating to technical description of land and other surveying matters. 2. Assistant Chief of Party – the person whose duty is to assist the chief of party in the accomplishment of the task assigned to the survey part. He takes over the duties of the chief of party during the absence of the chief. - He conducts ground reconnaissance and investigates sites of a proposed project to gather necessary data prior to the start of a survey work. - He is primarily responsible for the employment of surveying equipment, instruments and accessories used in the survey operation. - He prepares field and office reports and survey plan for submission to the chief party. 3. Instrumentman – the person whose duty is to set up, level, and operate surveying instruments. - He sees to it that instruments to be used in a survey operation are in good working condition and in proper adjustment. - He also assists the technician in the operation of electronic surveying equipment. - He works in coordination and as a part of an instrument party and exercises limited supervision over personnel doing manual tasks. 4. Technician – the person who is responsible for use and operation of all electronic instruments required in a field work operation. - It is his duty to see to it that these equipment are functioning properly, are regularly calibrated, and are in proper adjustment. - He is also responsible for the establishment of a two- way communication link by radio between members of the survey party where distant stations or long survey lines are involved. 5. Computer – the person whose duty is to perform all computations of survey data and works out necessary computational checks required in a field work operation. - He is responsible for the utilization of electronic calculators, computerized surveying systems or equipment. 6. Recorder- the person whose duty is to keep a record of all sketches, drawings, measurements and observations taken or needed for a field work operation. - He keeps table of schedules of all phases of work and the employment of the members of the survey party. - He does clerical task related to surveying in the office and undertakes limited cartographic jobs. 7. Head Tapeman – the person responsible for the accuracy and speed of all linear measurements with tape. - He determines and directs the marking of stations to be occupied by the surveying instruments and directs the marking of stations to be occupied by the surveying instruments and directs the clearing out of obstructions along the line of sight. - He inspects and compares tapes for standard length prior to their use in taping operations and is responsible for eliminating or reducing possible errors and mistakes in taping. 8. Rear Tapeman- the person whose duty is to assist the head tapeman during taping operations and in other related work. 9. Flagman – the person whose duty is to hold the flagpole or range pole at selected points as directed by the instrumentman. - He helps the tapeman in making measurement and assists the axeman in cutting down branches and in clearing other obstructions to line of sight. - Where electronic distance measuring instruments are used, he is responsible for setting up reflectors or targets. 10. Rodman – the person whose primary duty is to hold the stadia or leveling rod when sights are to be taken on it. 11. Pacer – the person whose duty is to check all linear measurements made by the tapeman. - He assists the tapeman in seeing to it that mistakes and blunders in linear measurements are either reduced or eliminated. - He may also perform the job of a rodman. 12. Axeman/Lineman – the person whose duty is to clear the line of sight of trees, brush, and other obstructions in wooded country. - He is also responsible for the security and safety of the members of the survey party at the survey site. - The axeman is usually provided not only with an ax but a rifle or a sidearm as well. If this member is to carry any firearm, it should be seen to it that he is advisable to request military or police authorities for needed security or hire authorized security guards. 13. Aidman – the person whose duty is to render first aid treatment to members of the survey party who are involved in snake and insects bites, accidents, and other cases involving their health, safety, and well being. - he may designated as an assistant instrumentman. 14. Utilitymen – the persons whose duties are to render other forms of assistance needed by the survey party or as directed by the chief of party. - where a survey vehicle is used, a utilityman is designated as a driver. - if the survey party has to camp out for days in the field, utilitymen are responsible for setting up the camp site. They are responsible for the handling and transporting of surveying equipment, accessories, and supplies. - the laying of concrete monuments, markers and signals at designated points are also their responsibility.