Based on their structure, questions can ‘lead’ respondents to a particular … These sources of errors in total station is discussed. %���� 3 0 obj Surveying 8. 1 0 obj endobj 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 may also be due to variations in natural phenomena such as temperature, humidity, wind, refraction and magnetic declination. Sampling and Sample Frame Errors. <>>>/Length 32>> The error can be … Winner of the Standing Ovation Award for “Best PowerPoint Templates” from Presentations Magazine. Basics of Tacheometry and Stadia System; Non-stadia Systems; Measurement of Absolute Direction . stream 2 0 obj Total station is a device used in surveying by replacing total station. The points to be observed must be below the level of the instrument, but not lower than the height of the staff. Accidental errors: These are the kind of errors which occur accidentally and can of any nature positive or negative. Time to time checking of the chain helps to provide ad… The details of the localized areas are measured and plotted with respect to the secondary control points. Introduction to Astronomy; Azimuth - its determination; Field Method of Hour Angle (Based on Sun observation) Control Survey . %PDF-1.5 Backsight and foresight distances should be approximately equal to avoid any errors due to collimation, refraction or earth curvature. This is an axial error. stream <> <> ��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+:'���� <> 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�"���. BASICS OF SURVEYING 1.1 SURVEYING DEFINED Surveying is the art of measuring distances, anglesand positionson or near the surface of the earth. Statisticians and survey methodologists judge the reliability and accuracy of a survey by looking at the errors that can occur in every survey. 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. (June 2015) (Learn how and when to remove this template message) Instrument errors are caused by imperfectly constructed, adjusted, or calibrated surveying equipment. The best way to avoid any problems with schedules is to not set expectations too high. Principle: 1 In surveying large areas, a system of control points are identified and they are located with high precision. Systematic errors, or biases errors, result from the physical properties of the measuring system. They may be positive and may change sign. Then secondary control points are located using lesser precise methods. It is the exercise of physically measuring horizontal distances. q 800 0 0 426 0 0 cm/Image6 Do Q 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. Writing down the wrong value, reading the instrument incorrectly, measuring to the wrong mark; these are gross errors. 2. Errors in surveying due to imperfection in measuring instruments and even imperfection of eyesight fall in this category. 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 Clients often get mad when a survey takes too long or has to be done a second time because the first map was incorrect. Accuracy ratio 1/10,000can be obtained using taping. endobj Like any device, total station also have some sources of error which can affect the surveying report. Line of sight error effects the horizontal angle readings and increases with steep sightings. <>/Pattern<>/Font<>/ProcSet[/PDF/Text/ImageB/ImageC/ImageI] >>/MediaBox[ 0 0 720 540] /Contents 4 0 R/Group<>/Tabs/S/StructParents 0>> 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. 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. ���� JFIF ` ` �� 6Exif II* &. 4 2 0 obj The mean angle is then equal to the sum of the total angle divided by the number of observations. Accidental Errors: Surveying errors can occur due to unavoidable circumstances like variations in atmospheric conditions which are entirely beyond the control of the observer. stream May 2005 SURVEYING EQUIPMENT, MEASUREMENTS AND ERRORS 3.1(5) Repetition MethodSuccessive measurements of an angle can be accumulated. All theodolites measure angles with some degree of imperfection. <>/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>> 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. The source of errors during observation are: INTRODUCTION TO TRAVERSE SURVEYING Traversing is a method of control survey to establish control points. This is used to provide distance estimates when no measuring device is available or precision is not required. stream If the length of the chain is long, then the measured distance is smaller and the error is negative. Chain survey is the simplest method of surveying. The survey tape is the most common, but other methods and devices are also used in highway work. endobj And when the length of the chain is short, then the measured distance is long. - Pacing Count the number of steps and multiply by the known length of each step. There are3 types of errors : Gross errors are those which we can also call `blunders'. Errors In Chain Surveying. <> A traverse must start with control station which is known station (known coordinate). x���_o�6���;�Qz0+���4[3 C�})��:na ���}��Q�CZSw���;R��g����۫������]~�b���g�~L�Zv���L� This error is a cumulative error that can either take a negative or a positive value. They'll give your presentations a professional, memorable appearance - the kind of sophisticated look that today's audiences expect. This article includes a list of references, related reading or external links, but its sources remain unclear because it lacks inline citations. Temperature Errors We have already seen that carbon steel changes length with the temperature. The 90 and 95% errors are used to specify precisions required for surveying projects. Horizontal collimation or line of sight error is when the line of sight is not perpendicular to the tilting axis of the instrument. endobj Experienced personnel may achieve a precision of 1/50. They can be of any size or nature, and tend to occur through carelessness. A traverse must start with control station which is known … 3 0 obj <>>> 4 0 obj If it is not properly observed while taking measurements, the … Errors may occur at any stage during the collection and processing of survey data, whether it is a census or a sample survey. Systematic errors are constant under constant measuring conditions and change as conditions change. Please help to improve this article by introducing more precise citations. %PDF-1.5 World's Best PowerPoint Templates - CrystalGraphics offers more PowerPoint templates than anyone else in the world, with over 4 million to choose from. (b) Elimination of parallax. What errors may affect the survey results? Distances must not be so great as to not be able to read the graduations accurately. 4 0 obj 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. 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. 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). Leading questions. Eliminate or correct all systematic errors by frequent calibration and adjustment of the instruments Minimize the random errors by using good instrumentsandfieldprocedures. surveying, the following strategies must be followed: Follow techniques that will help detect and eliminatealltheblunders. A classical example is the change in length of a tape as the temperature changes. Teodolite Measurement and Errors; Measurement of Horizontal and Vertical Distance Simultaneously . endobj ~�V�ʰ�2\Jv�t~V�x����kqWδ-�p5Ţ�Y��^+w�q�k�� %���� endobj A land surveyor should always play it safe when giving an … endstream This is the error due to the wrong length of the chain which is considered as one of the serious error. 1 0 obj <> 6 0 obj endstream This is a fact of life in construction and surveying. endobj 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. 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 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. Hence the error is positive. endobj Curvature and Refraction in Levelling | Surveying. 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) <>>> 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 … This field work will continue for 3 field hours. 1 Aug 18, 2014 Introduction to Surveying Chap. Leveling 9. 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. 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