{"id":791,"date":"2024-07-05T12:57:33","date_gmt":"2024-07-05T07:27:33","guid":{"rendered":"https:\/\/study.madeeasy.in\/?p=791"},"modified":"2025-07-16T14:58:12","modified_gmt":"2025-07-16T09:28:12","slug":"tangential-method-of-tacheometry","status":"publish","type":"post","link":"https:\/\/www.madeeasy.in\/study\/ce\/surveying\/tangential-method-of-tacheometry","title":{"rendered":"TANGENTIAL METHOD OF TACHEOMETRY"},"content":{"rendered":"<ul>\r\n<li style=\"text-align: justify;\">In the absence of stadia hairs, the tangential method of tacheometry is resorted to.<\/li>\r\n<li style=\"text-align: justify;\">This method is used when the staff is held too far from the instrument station and it is difficult to read the staff.<\/li>\r\n<li style=\"text-align: justify;\">Here the staff is fitted with two targets spaced at a fixed vertical distance (<em>s<\/em>) apart (say 2 m or 3 m). By sighting the two targets, the vertical angles \u00d8<sub>1<\/sub> and \u00d8\u00a0<sub>2<\/sub> are measured.<\/li>\r\n<li style=\"text-align: justify;\">From above three observations <em>s<\/em>, \u00d8<sub>1<\/sub> and \u00d8<sub>2<\/sub>, the horizontal distance <em>D <\/em>and vertical intercept <em>V <\/em>is arrived at as per the following three cases as described below.<\/li>\r\n<\/ul>\r\n<p style=\"text-align: justify;\"><strong>Case I: Both the Angles are at Elevation<\/strong><\/p>\r\n<p style=\"text-align: justify;\"><img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-477 aligncenter\" src=\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2024\/07\/both-the-angles-elevatio.jpg\" alt=\"Both the Angles are at Elevation\" width=\"729\" height=\"594\" \/><\/p>\r\n<p style=\"text-align: justify;\"><img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-478 aligncenter\" src=\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2024\/07\/angles-are-depression.jpg\" alt=\"Angles are at Depression\" width=\"640\" height=\"194\" \/><\/p>\r\n<p style=\"text-align: justify;\"><img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-480 aligncenter\" src=\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2024\/07\/tangible-method.jpg\" alt=\"\" width=\"545\" height=\"375\" \/><\/p>\r\n<p style=\"text-align: justify;\"><img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-481 aligncenter\" src=\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2024\/07\/depression.jpg\" alt=\"Depression\" width=\"651\" height=\"480\" \/><\/p>\r\n<p style=\"text-align: justify;\"><img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-482 aligncenter\" src=\"https:\/\/study.madeeasy.in\/wp-content\/uploads\/2024\/07\/instrument.jpg\" alt=\"Instrument\" width=\"507\" height=\"81\" \/><\/p>\r\n<p style=\"text-align: justify;\"><strong>Errors Due to Personnel Reasons<\/strong><\/p>\r\n<ul style=\"text-align: justify;\">\r\n<li style=\"list-style-type: none;\">\r\n<ul>\r\n<li><strong>Error due to faulty centering, levelling and bisections:<\/strong> If the tacheometer is not centered and levelled properly then errors may creep in.<\/li>\r\n<li><strong>Error due to non-verticality of staff:<\/strong> Often the staff may not be held perfectly vertical due to which error incurs. A plumb bob provided with the staff ensures the verticality of staff.<\/li>\r\n<li><strong>Error due to wrong reading of staff:<\/strong> The staff intercept if not read correctly then this introduces error. Thus it is always advisable to read the staff readings for all the three stadia wires and to check whether difference of readings of upper and middle stadia is equal to difference of readings of middle and lower stadia.<\/li>\r\n<li><strong>Error due to faulty reading of vertical angle:<\/strong> Tacheometry also involves the measurement of vertical angle and the same should be done precisely otherwise appreciable errors may occur in the results.<\/li>\r\n<\/ul>\r\n<\/li>\r\n<\/ul>\r\n<div id=\"ez-toc-container\" class=\"ez-toc-v2_0_79_1 ez-toc-wrap-left counter-hierarchy ez-toc-counter ez-toc-light-blue ez-toc-container-direction\">\n<div class=\"ez-toc-title-container\">\n<p class=\"ez-toc-title\" style=\"cursor:inherit\">Table of Contents<\/p>\n<span class=\"ez-toc-title-toggle\"><a href=\"#\" class=\"ez-toc-pull-right ez-toc-btn ez-toc-btn-xs ez-toc-btn-default ez-toc-toggle\" aria-label=\"Toggle Table of Content\"><span class=\"ez-toc-js-icon-con\"><span class=\"\"><span class=\"eztoc-hide\" style=\"display:none;\">Toggle<\/span><span class=\"ez-toc-icon-toggle-span\"><svg style=\"fill: #999;color:#999\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" class=\"list-377408\" width=\"20px\" height=\"20px\" viewBox=\"0 0 24 24\" fill=\"none\"><path d=\"M6 6H4v2h2V6zm14 0H8v2h12V6zM4 11h2v2H4v-2zm16 0H8v2h12v-2zM4 16h2v2H4v-2zm16 0H8v2h12v-2z\" fill=\"currentColor\"><\/path><\/svg><svg style=\"fill: #999;color:#999\" class=\"arrow-unsorted-368013\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"10px\" height=\"10px\" viewBox=\"0 0 24 24\" version=\"1.2\" baseProfile=\"tiny\"><path d=\"M18.2 9.3l-6.2-6.3-6.2 6.3c-.2.2-.3.4-.3.7s.1.5.3.7c.2.2.4.3.7.3h11c.3 0 .5-.1.7-.3.2-.2.3-.5.3-.7s-.1-.5-.3-.7zM5.8 14.7l6.2 6.3 6.2-6.3c.2-.2.3-.5.3-.7s-.1-.5-.3-.7c-.2-.2-.4-.3-.7-.3h-11c-.3 0-.5.1-.7.3-.2.2-.3.5-.3.7s.1.5.3.7z\"\/><\/svg><\/span><\/span><\/span><\/a><\/span><\/div>\n<nav><ul class='ez-toc-list ez-toc-list-level-1 ' ><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-1\" href=\"https:\/\/www.madeeasy.in\/study\/ce\/surveying\/tangential-method-of-tacheometry\/#Instrumental-Errors\" >Instrumental Errors<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"https:\/\/www.madeeasy.in\/study\/ce\/surveying\/tangential-method-of-tacheometry\/#Error-Due-to-Natural-Causes\" >Error Due to Natural Causes<\/a><\/li><\/ul><\/nav><\/div>\n<h3 style=\"text-align: justify;\"><span class=\"ez-toc-section\" id=\"Instrumental-Errors\"><\/span>Instrumental Errors<span class=\"ez-toc-section-end\"><\/span><\/h3>\r\n<ul style=\"text-align: justify;\">\r\n<li><strong>Error due to faulty instrument constants:<\/strong> With continuous use of instrument (i.e., tacheometry), the instrument constants k and C may get changed. The erroneous effect due to this is cumulative in nature. Thus it is quite essential to verify the instrument constants regularly.<\/li>\r\n<li><strong>Error due to imperfect adjustment of instrument:<\/strong> Certain adjustments of the instrument are done in factory only and thus if instrument is having fault in its factory production, then error may get introduced.<\/li>\r\n<li><strong>Error due to stadia rod:<\/strong> Faulty divisions in stadia rod and improper standardization lead to errors.<\/li>\r\n<\/ul>\r\n<h3 style=\"text-align: justify;\"><span class=\"ez-toc-section\" id=\"Error-Due-to-Natural-Causes\"><\/span>Error Due to Natural Causes<span class=\"ez-toc-section-end\"><\/span><\/h3>\r\n<ul>\r\n<li style=\"text-align: justify;\"><strong>Wind:<\/strong> Very strong wind currents disturb the work and readings in field cannot be taken correctly. Apart from that, strong winds make it difficult to hold the staff truly vertical.<\/li>\r\n<li style=\"text-align: justify;\"><strong>Sun:<\/strong> In hot sunny days unequal expansion of instrument parts take place and is a source of error.<\/li>\r\n<li style=\"text-align: justify;\"><strong>Atmospheric refraction:<\/strong> Atmospheric refraction changes the path of line of sight thereby giving wrong staff readings. Thus for very long sights, read only the top and middle hair and multiply the difference of top and middle hair readings by two to get the staff intercept.<\/li>\r\n<\/ul>\r\n\r\n<p style=\"text-align: center;\"><a class=\"btn btn-danger\" role=\"button\" href=\"https:\/\/study.madeeasy.in\/ce\/surveying\/principle-of-stadia-method-of-tacheometry\/\" target=\"_blank\" rel=\"noopener\">&lt;&lt; Previous<\/a> | <a class=\"btn btn-success\" role=\"button\" href=\"https:\/\/study.madeeasy.in\/ce\/surveying\/principle-of-triangulation\/\" target=\"_blank\" rel=\"noopener\"> Next &gt;&gt;<\/a> <br \/><strong> Must Read: <\/strong> <a href=\"https:\/\/study.madeeasy.in\/subjects\/what-is-surveying\/\" target=\"_blank\" rel=\"noopener\"><strong>What is Surveying?<\/strong><\/a><\/p>\r\n<p>&nbsp;<\/p>\r\n","protected":false},"excerpt":{"rendered":"<p>In the absence of stadia hairs, the tangential method of tacheometry is resorted to. This method is used when the<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[203,2],"tags":[270,271,272],"class_list":["post-791","post","type-post","status-publish","format-standard","hentry","category-surveying","category-ce","tag-error-due-to-natural-causes","tag-errors-due-to-personnel-reasons","tag-instrumental-errors"],"_links":{"self":[{"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/posts\/791","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/comments?post=791"}],"version-history":[{"count":0,"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/posts\/791\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/media?parent=791"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/categories?post=791"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.madeeasy.in\/study\/wp-json\/wp\/v2\/tags?post=791"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}