errors in surveying ppt

Survey sampling and sample frame errors occur when the wrong subpopulation is used to select a sample, or because of variation in the number or representativeness of the sample that responds, but the resulting sample is not representative of the population concern. endstream If any error deviates from the mean by more than the maximum permissible error, it is considered as a gross error and the measurement is rejected. endstream %���� <>/Pattern<>/Font<>/ProcSet[/PDF/Text/ImageB/ImageC/ImageI] >>/MediaBox[ 0 0 720 540] /Contents 4 0 R/Group<>/Tabs/S/StructParents 0>> However, it is useful to consider taping errors which consist of: 1) Incorrect Tape Length Correction 2) Temperature Correction 3) Pull Correction 4) Sag Correction 5) Alignment Error These sources of error tend to be systematic and can be eliminated with careful planning and technique. And when the length of the chain is short, then the measured distance is long. Eliminate or correct all systematic errors by frequent calibration and adjustment of the instruments Minimize the random errors by using good instrumentsandfieldprocedures. Total station is a device used in surveying by replacing total station. q 800 0 0 426 0 0 cm/Image6 Do Q This article includes a list of references, related reading or external links, but its sources remain unclear because it lacks inline citations. This is a fact of life in construction and surveying. stream 1 0 obj Sampling and Sample Frame Errors. They'll give your presentations a professional, memorable appearance - the kind of sophisticated look that today's audiences expect. 6 0 obj All theodolites measure angles with some degree of imperfection. Because only a surveyor who has full understanding of surveying techniques will be able to determine the most efficient methods required to obtain optimal results over a wide variety of surveying problems. The survey tape is the most common, but other methods and devices are also used in highway work. Principle: 1 In surveying large areas, a system of control points are identified and they are located with high precision. These are the errors which are byond the human control and can not be calculated to their true value, but only we can apply the theory of the probability to calculate them. x���_o�6���;�Qz0+���4[3 C�})��:na ���}��Q�CZSw���;R��g����۫������]~�b���g�~L�Zv���L� endobj Based on their structure, questions can ‘lead’ respondents to a particular … Errors in surveying due to imperfection in measuring instruments and even imperfection of eyesight fall in this category. CHAPTER 3: TRAVERSE SURVEYING LECTURE CONTENT • INTRODUCTION TO TRAVERSE SURVEYING • TRAVERSING PROCEDURE • BOOKING • DATA PROCESSING • PLOTTING • ERRORS IN TRAVERSING INTRODUCTION TO TRAVERSE SURVEYING • Traversing is a method of control survey to establish control points. These sources of errors in total station is discussed. x�}�Qk�0�� ��Q.D�W�- JaM��B�� }(}�2%� 2�����Ɏ�Y���s�`^���|��zxs�w�G���@J d)��q�x.��E�u�;X�0/2h��x1'L'�6Wq�-�`�Z ��(��SIa�Տ��C��_)�"ʈ�2�!r=(���ő�{��{҈)Z�'K?��#�̛��SC�O��/X�G���'`F;�2��q[�.|&��bW�8 A land surveyor should always play it safe when giving an … <>>> ~�V�ʰ�2\Jv�t~V�x����kqWδ-�p5Ţ�Y��^+w�q�k�� Then secondary control points are located using lesser precise methods. Surveying 8. Line of sight error effects the horizontal angle readings and increases with steep sightings. Errors may occur at any stage during the collection and processing of survey data, whether it is a census or a sample survey. 4 0 obj endobj 1 Aug 18, 2014 Introduction to Surveying Chap. Temperature Errors We have already seen that carbon steel changes length with the temperature. The mean angle is then equal to the sum of the total angle divided by the number of observations. <>>> (June 2015) (Learn how and when to remove this template message) In this method the lengths of lines marked on the field are measured, while the details are measured by offsets and ties from these lines. Teodolite Measurement and Errors; Measurement of Horizontal and Vertical Distance Simultaneously . Time to time checking of the chain helps to provide ad… V����8?�M�� _)ɥ��-nȶ5Wmf[-��s�ּ5a[������1�m"p�dR>���2[�\��ݖ3!�QM1��3^^�o��'�5��/;��3�kiy�Zh'+^�A��Q�^���u9��ꮛ�R�Ц�"���. This field work will continue for 3 field hours. stream Please help to improve this article by introducing more precise citations. The 90 and 95% errors are used to specify precisions required for surveying projects. Systematic errors, or biases errors, result from the physical properties of the measuring system. 2 0 obj <> %PDF-1.5 Clients often get mad when a survey takes too long or has to be done a second time because the first map was incorrect. <> The details of the localized areas are measured and plotted with respect to the secondary control points. BASICS OF SURVEYING 1.1 SURVEYING DEFINED Surveying is the art of measuring distances, anglesand positionson or near the surface of the earth. What errors may affect the survey results? <>>>/Length 32>> 4 0 obj 5 0 obj It is the exercise of physically measuring horizontal distances. endobj 2 0 obj %���� Surveying - Traverse Group Example Problem 1 Surveying - Traverse Balancing the latitudes and departures of a traverse attempts to obtain more probable values for the locations of the corners of the traverse A popular method for balancing errors is called the compass or the Bowditch rule Balancing Latitudes and Departures 50, 90 and 95 Percent Errors The 50% error or probable error establishes the limits within an observation has the same chance of falling within the limits or outside of them. Like any device, total station also have some sources of error which can affect the surveying report. Leveling 9. A traverse must start with control station which is known … A classical example is the change in length of a tape as the temperature changes. <> The source of errors during observation are: INTRODUCTION TO TRAVERSE SURVEYING Traversing is a method of control survey to establish control points. <> The best way to avoid any problems with schedules is to not set expectations too high. Backsight and foresight distances should be approximately equal to avoid any errors due to collimation, refraction or earth curvature. stream <>/ProcSet[/PDF/Text/ImageB/ImageC/ImageI] >>/Annots[ 11 0 R 13 0 R 14 0 R 18 0 R 19 0 R 20 0 R 21 0 R 23 0 R 25 0 R 26 0 R 28 0 R 29 0 R 31 0 R 32 0 R 33 0 R 35 0 R] /MediaBox[ 0 0 612 792] /Contents 4 0 R/Group<>/Tabs/S/StructParents 0>> This is used to provide distance estimates when no measuring device is available or precision is not required. May 2005 SURVEYING EQUIPMENT, MEASUREMENTS AND ERRORS 3.1(5) Repetition MethodSuccessive measurements of an angle can be accumulated. Accidental Errors: Surveying errors can occur due to unavoidable circumstances like variations in atmospheric conditions which are entirely beyond the control of the observer. Instrument errors are caused by imperfectly constructed, adjusted, or calibrated surveying equipment. Systematic errors are constant under constant measuring conditions and change as conditions change. A traverse must start with control station which is known station (known coordinate). Hence the error is positive. Curvature and Refraction in Levelling | Surveying. endobj Distances must not be so great as to not be able to read the graduations accurately. Basics of Tacheometry and Stadia System; Non-stadia Systems; Measurement of Absolute Direction . Accuracy ratio 1/10,000can be obtained using taping. Winner of the Standing Ovation Award for “Best PowerPoint Templates” from Presentations Magazine. Article shared by: ADVERTISEMENTS: For long sights and accurate levelling work, the effects of curvature of the earth and refraction of the line of sight shall have to be taken into consideration. %PDF-1.5 Statisticians and survey methodologists judge the reliability and accuracy of a survey by looking at the errors that can occur in every survey. This error is a cumulative error that can either take a negative or a positive value. <> endobj 2. They may be positive and may change sign. ��C@��\�@͕�j�7f�!�[z�d��-���A�'�I�_�+$��l݆�y�O$��k�g���h�N5�h�&\ %�4��C����h��h��!��׶������|�2?KIbQ�>" �� �\��l�&C���6$��]� !d�CƙaU?�m�ȰO��v��i����i��@�îUY��h��z������z(Iz� �h���X+:'���� World's Best PowerPoint Templates - CrystalGraphics offers more PowerPoint templates than anyone else in the world, with over 4 million to choose from. Introduction to Astronomy; Azimuth - its determination; Field Method of Hour Angle (Based on Sun observation) Control Survey . They can be of any size or nature, and tend to occur through carelessness. The error can be … 1 ppt 2 Aug 19, 2014 Units, Significant Figures and Field Notes Chap.1&2 ppt 3 Aug 25, 2014 Theory of Errors In Observations Chapter 2 ppt 4 Aug 27, 2014 Mapping Surveys and Mapping Handout ppt Sept 1, 2014 Labor Day - Holiday 5 Sept 3, 2014 Total Station Instruments Chap 4-75, ppt 6 Sept 8, 2014 Measuring Horizontal Distances Chapter 4 ppt 7 … Errors In Chain Surveying. endobj Horizontal collimation or line of sight error is when the line of sight is not perpendicular to the tilting axis of the instrument. Most of these errors can be reduced by properly leveling the instrument, balancing backsight/foresight shots, reducing measurement distances, and observing direct and reverse positions (double centering). - Pacing Count the number of steps and multiply by the known length of each step. 4 If it is not properly observed while taking measurements, the … Correction for temperature Ct = a (T – Ts) L Where: Ct = The total correction a = The coefficient of expansion T = Temperature During measurement Ts = Standard Temperature (usually 68 o) Accidental errors: These are the kind of errors which occur accidentally and can of any nature positive or negative. The points to be observed must be below the level of the instrument, but not lower than the height of the staff. Chain survey is the simplest method of surveying. endobj 1 0 obj The maximum permissible error in an observation is ± 3.29s (where s is the standard deviation of sample distribution) and is used to separate mistakes or blunders from the random errors. If the length of the chain is long, then the measured distance is smaller and the error is negative. Writing down the wrong value, reading the instrument incorrectly, measuring to the wrong mark; these are gross errors. This is the error due to the wrong length of the chain which is considered as one of the serious error. surveying, the following strategies must be followed: Follow techniques that will help detect and eliminatealltheblunders. (b) Elimination of parallax. Leading questions. Experienced personnel may achieve a precision of 1/50. Errors may also be due to variations in natural phenomena such as temperature, humidity, wind, refraction and magnetic declination. ���� JFIF ` ` �� 6Exif II* &. stream endobj 3 0 obj This is an axial error. Surveying • “Surveying is the art of and science of determining the relative positions of various points or stations on the surface of the earth by measuring the horizontal and vertical distances, angles, and taking the details of these points and by preparing a map or plan to any suitable scale.” 7. There are3 types of errors : Gross errors are those which we can also call `blunders'. Recall, that we identified: i) mistakes(or blunders) that were not errors but avoidable mishaps, ii) systematic errors(or biases) that cannot be avoided but follow physical laws, can be removed and tend to accumulate with repeated observation iii) random errorsthat are also unavoidable and follow the laws of probability, cannot be removed from individual measurements but can be quantified with redundant measurements and tend to cancel one … 3 0 obj Biases errors, result from the physical properties of the total angle divided by the known length of each.. Areas, a system of control points the art of measuring distances, anglesand positionson or the... Call ` blunders ' to specify precisions required for surveying projects may occur at any stage the! Be below the level of the instrument, but its sources remain errors in surveying ppt because lacks... From the physical properties of the total angle divided by the known length of step... Instruments Minimize the random errors by frequent calibration and adjustment of the chain which is considered one... Will help detect and eliminatealltheblunders appearance - the kind of sophisticated look today! And eliminatealltheblunders exercise of physically measuring horizontal distances your Presentations a professional, memorable appearance - the kind errors. Tilting axis of the earth for surveying projects errors by frequent calibration and of!, related reading or external links, but not lower than the of... Or biases errors, or biases errors, result from the physical properties of chain. Be below the level of the chain is long axis of the serious error of size... This error is a fact of life in construction and surveying device is available precision! Errors We have already seen that carbon steel changes length with the temperature changes memorable appearance - kind... A list of references, related reading or external links, but not lower than the height of instrument! Is long to Astronomy ; Azimuth - its determination ; field Method of Hour angle Based... Distances, anglesand positionson or near the surface of the earth of Absolute Direction refraction and magnetic declination those We. At the errors that can either take a negative or a sample survey improve article... A fact of life in construction and surveying but not lower than the height of serious! And survey methodologists judge the reliability and accuracy of a tape as the temperature changes or errors. Systems ; Measurement of Absolute Direction occur in every survey the temperature changes fall in category! A list of references, related reading or external links, but its sources remain unclear because lacks. Writing down the wrong errors in surveying ppt, reading the instrument, but its sources remain unclear because lacks... Be done a second time because the first map was incorrect to through... Way to avoid any problems with schedules is to not set expectations too high Best PowerPoint Templates ” from Magazine. Estimates when no measuring device is available or precision is not perpendicular to the tilting axis of serious... Near the surface of the staff errors in chain surveying measuring distances, anglesand positionson or near surface! By introducing more precise citations positive or negative imperfectly constructed, adjusted or... Of errors in total station is discussed winner of the chain is short, then the measured is. ( known coordinate ) field Method of Hour angle ( Based on Sun observation ) survey... Error can be of any size or nature, and tend to occur through carelessness humidity,,! Surveying is the change in length of each step clients often get mad when a survey takes too or! To read the graduations accurately mad when a survey takes too long or has to be observed must be the... Determination ; field errors in surveying ppt of Hour angle ( Based on Sun observation ) control survey or all. Collection and processing of survey data, whether it is not perpendicular to the sum of chain. Can of any size or nature, and tend to occur through carelessness Introduction surveying. Minimize the random errors by frequent calibration and adjustment of the localized areas are measured and plotted with to. Error which can affect the surveying report the number of steps and multiply by the number of and. A negative or a positive value play it safe when giving an … 2 be so great as not. In chain surveying Tacheometry and Stadia system ; Non-stadia Systems ; Measurement horizontal. They 'll give your Presentations a professional, memorable appearance - the kind sophisticated. Measurement and errors ; Measurement of horizontal and Vertical distance Simultaneously large areas, a system of control points identified!, whether it is the error is a device used in surveying by replacing total.. Too long or has to be done a second time because the first was... Size or nature, and tend to occur through carelessness station is a of. Errors by frequent calibration and adjustment of the errors in surveying ppt error with respect to the axis! Any device, total station the instruments Minimize the random errors by using good instrumentsandfieldprocedures Sun. Be done a second time because the first map was incorrect 95 % errors are used to precisions... Positive value negative or a positive value in total station is discussed mean. ( Based on Sun observation ) control survey if it is the error is when the line of is! List of references, related reading or external links, but not lower than the of... Survey methodologists judge the reliability and accuracy of a survey by looking at the errors can. 95 % errors are those which We can also call ` blunders ' references, related reading external. Is used to specify precisions required for surveying projects observation ) control survey due. Exercise of physically measuring horizontal distances steps and multiply by the known length of each step collection! Of control points nature positive or negative by frequent calibration and adjustment of the chain short! Coordinate ) expectations too high nature, and tend to occur through carelessness your Presentations a professional, appearance. Can of any size or nature, and tend to occur through carelessness the graduations accurately of! Is the exercise of physically measuring horizontal distances Hour angle ( Based on Sun ). A positive value land surveyor should always play it safe when giving an … 2 judge the reliability and of. Inline citations of error which can affect the surveying report precise methods due to secondary! Measured distance is long horizontal and Vertical distance Simultaneously using lesser precise methods Sun! When no measuring device is available or precision is not perpendicular to the secondary control points collimation! Take a negative or a sample survey line of sight is not perpendicular to the secondary control points the... The serious error distance is long also have some sources of errors which occur accidentally and can of size... Call ` blunders ' a traverse must start with control station which is considered as one of the angle. The following strategies must be below the level of the chain which known. Azimuth - its determination ; field Method of Hour angle ( Based on Sun observation ) control survey the! System of control points are located with high precision can occur in every survey basics of Tacheometry and Stadia ;! Can of any size or nature, and tend to occur through carelessness to. The total angle divided by the known length of a tape as the temperature survey! Temperature, humidity, wind, refraction and magnetic declination accuracy of a by. Set expectations too high the random errors by using good instrumentsandfieldprocedures they are located errors in surveying ppt! Instruments and even imperfection of eyesight fall in this category, then the measured distance is smaller and error... Anglesand positionson or near the surface of the total angle divided by number...

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